THE ELECTREC MOMENTS OF SOME
ALEPHATIC HYDROCARBQNS AND THE
ELECTRIC MOMENTS AND
CONFORMATEONAL ANALYSIS OF SOME
D UHALCGENO - AND DEKETO - CYCLOH EXANES

Thests for the Degree of DE. D.
MICHKGAN STATE UMVERSETY
James Marquess Canon

1961

mm”- ._ flmw .__—$ 4-

THESlS

 

This is to certify that the

thesis entitled

The Electric Moments of Some Aliphatic Hydrocarbons
and the Electric Moments and Conformational
-Ana1ysis of Some Dihalogeno- and Kiketo-Cyclohexanes

presented by

Jame s Marque 56 Canon

has been accepted towards fulfillment
of the requirements for

Ph. D. degree in hemistry

 

 

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Michigan State

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ABSTRACT

THE ELECTRIC MOMENTS OF SOME ALIPHATIC HYDROCARBONS
AND THE ELECTRIC MOMENTS AND CONFORMATIONAL
ANALYSIS OF SOME DII-IALOGENO- AND DIKETO-CYCLOHEXANES

by James Marquess Canon

The electric moments of 2-methy1propane, 2-methy1butane,

cis-Z-butene, trans-Z-butene, 3-methy1-l-butyne, 3,3-dimethy1-1-

 

butyne, £1318: l, Z-dibromocyclohexane, gals: l-bromo-Z-chlorocyclo-
hexane, m—l, 2-dichlorocyclohexane, and 1, 4-cyclohexanedione have
been measured in the vapor phase. Small moments were found for both
Z-methylpropane and Z-methylbutane. A value of the electric moment of

cis-Z-butene somewhat smaller than expected may be explained by con-

 

sideration of the resonance structures. The variation of electric moment
with structure in the aliphatic mono-acetylenes may be attributed to
dipole-induced-dipole interaction and calculated from polarizability data.
Energy differences between conformational isomers of the halogen
compounds were calculated from the data. For 1, 4-cyclohexanedione

the experimental data permitted qualitative limits to be set for the

difference in energy between conformational isomers.

THE ELECTRIC MOMENTS OF SOME ALIPHATIC HYDROCARBONS
AND THE ELECTRIC MOMENTS AND CONFORMATIONAL
ANALYSIS OF SOME DIHALOGENO- AND DIKETO-CYCLOHEXANES

BY

Jame s Marque s 3 Canon

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCT OR OF PHILOSOPHY

Department of Chemi stry

1961

ACKNOWLEDGMENT

The author wishes to express his sincere
appreciation to Professor M. T. Rogers for his
guidance and encouragement throughout the
course of his graduate studies.

. He wishes further to acknowledge gratefully
the assistance of Mr. Forest E. Hood and Mr.
Frank Betts in the construction of the experimental
apparatus.

Gratitude is also extended to the National
Science Foundation and to The Upjohn Company for

grants of financial assistance which have in part
supported this research.

**#********

ii

VITA

James Marquess Canon
Candidate for the degree of

Doctor of Philo s Ophy

Major Field of Study: Physical Chemistry
Minor Fields of Study: Organic Chemistry and Physics
Biographical:

Born, March 13, 1924 in Waco, Texas

Bachelor of Arts in Economics, University of Michigan,
Ann Arbor, Michigan, 1950

Bachelor of Science in Chemistry, Western Michigan
University, Kalamazoo, Michigan, 1955

Graduate Studies in Physical Chemistry and Allied
Sciences, Michigan State University, East Lansing,
Michigan, 1955-1960

iii

TABLE OF CONTENTS

INTRODUCTION .........................
THEORY .............................
EXPERIMENTAL METHODS ..................

The Capacitance Cell . . .................
Capacitance Measurement .................
Temperature Control and Measurement .........
Pressure Measurement . . . ...............
The Material Handling System ...............

PROCEDURES ..........................

Constant Temperature Bath ................
Measurements .......................
Low Boiling Materials ...................
High Boiling Materials ..................

DATA AND CALCULATIONS ..................

The Cell Constant and the Dielectric Constant of
Ammonia ........................
Molar Volumes and Molar Polarization ........
Molar Refractions .......... . ........ . .
Dipole Moments and Distortion Polarizations ......

RESULTS .............................
ANALYSIS OF ERROR . . . ..................
DISCUSSION OF RESULTS . ..................
SUMMARY ............................
LITERATURE CITED . . . . ..................

iv

LIST OF TABLES

TABLE

II.

III.
IV.

VI.
VII.
VIII.
IX .

XI.
XII.
XIII.
XIV.

‘ XV.
XVI.
XVII.
XVIII.

XIX.
XX.

XXI.

XXII.

. Vapor Phase Electric Moments of Hydrocarbons . . . .

Solution Electric Moments and Isomeric Energy Dif-
ferences in Substituted Cyclohexanes ..........

Physical Constants of Subject Materials .........

Calculated Dielectric Constants of Ammonia ......

. Vander Waal's Parameters . . . . . . . . . . .....

Capacitance-Pressure Data for Z-Methylpropane . . . .
Molar Polarization Data for Z-Methylpropane ......
Capacitance-Pressure Data for Z-Methylbutane .....

Molar Polarization Data for Z-Methylbutane .......

. Capacitance-Pressure Data for cis Z-Butene ......

 

Molar Polarization Data for cis Z-Butene ........

 

Capacitance-Pressure Data for trans Z-Butene .....

 

Molar Polarization Data for trans Z-Butene .......

 

Capacitance-Pressure Data for 3-Methy1-l-butyne . . .
Molar Polarization Data for 3-Methyl-1-butyne .....
Capacitance-Pressure Data for 3, 3-Dimethy1-l-butyne.
Molar Polarization Data for 3, 3-Dimethy1-l-butyne . .

Capacitance-Pressure Data for 1, 2-Dibromocyclo-
hexane .........................

Molar Polarization Data for l, 2-Dibromocyclohexane .

Capacitance-Pressure Data for l-Bromo-Z-Chloro-
cyclohexane ......................

Molar Polarization Data for l-Bromo-Z-Chlorocyclo-
hexane ..................... . . . .

Capacitance-Pressure Data for 1, 2-Dichlorocyclo-
hexane . .........................

Page

15
41
42
44
45
47
48
50
51
53
54
56
57
59
61

63
63

64

64

65

LIST OF TABLES - Continued
TABLE

XXIII.
XXIV .
XXV.
XXVI.
XXVII.

XX VIII.
XXIX .

XXX .

Molar Polarization Data for 1, 2-Dichlorocyclohexane. .

Capacitance—Pressure Data for l, 4-Cyclohexanedione
Molar Polarization Data for 1, 4-Cyclohexanedione . .
Dipole Moments of Hydrocarbons ..........

Dipole Moments and Isomeric Energy Differences of
Substituted Cyclohexanes . . . . . . .........

Experimental Error .................. . .. .

Group Polarizabilities . . . . . . . ...........

Energy Differences Between Conformational Isomers

for Some trans-1, Z-Dihalogenocyclohexanes .......

 

vi

Page

65
66
66
68

68
73

79

84

LIST OF FIGURES

FIGURE ' Page
1. The capacitance cell ................... . 17
2. Block diagram of heterodyne-beat apparatus ...... 18
3. The balancing network .................. l9
4. The heterodyne-beat apparatus ............ .. 22
5. The constant temperature bath ........... . .. 25
6. The temperature control circuit ............. 27
7. The pressure switch .................. _, 3O
8. The manometer control system ............. 31
9. The materials handling system ............ . 33

10. Molar polarization versus the reciprocal of the abso-

lute temperature for 2-methy1propane .......... 46

11. Molar polarization versus the reciprocal of the
absolute temperature for 2-methy1butane ........ 49

12. Molar polarization versus the reciprocal of the
absolute temperature for cis-Z-butene ......... 52

 

13. Molar polarization versus the reciprocal of the
absolute temperature for trans-Z-butene ........ 55

 

14. Molar polarization versus the reciprocal of the
absolute temperature for 3-methy1-1-butyne ...... 58

15. Molar polarization versus the reciprocal of the
absolute temperature for 3, 3-dimethy1-1-butyne . . . . 62

vii

INTRODUCTION

In 1912 P. Debye (1) showed that when the dielectric constant of
a substance is not a constant, but varies with temperature, the explana-
tion is to be found in consideration of the distribution of positive and
negative electrical charges in molecules of the substance. This concept,
the electric dipole moment, was subsequently developed by Smyth (3),
Errara (4), and others (2, 5) in terms of individual bond moments which
combined to yield the molecular moment. As a further development of
this point of view moment values were empirically assigned (6, 7) to a
large number of Specific inter-atomic bonds, the vector addition of
which could be used to predict with considerable accuracy the electric
moments of many molecules. Finally, and perhaps more important than
a basis for the prediction of the property itself, a series of conventions
came into being by means of which variance between predicted and
measured values could be explained. These conventions, which ranged
from the somewhat qualitative inductive effects, through steric electro-
static repulsions and attractions, to the quantum mechanical concept of
resonance were, until the 1950's, virtually the only experimentally
supported insight into the electronic configurations of molecules.

The electric moments of thousands of polar molecules have been
determined over the years, but of these only a few--1ess than 400--have
been determined in the vapor phase, the only state in which, in theory,
the Debye equation strictly applies. In some instances experimental
results have been rendered ambiguous by reason of the unknown inter-
ferences of the solvent in solution measurements while in other instances
vapor phase measurements have failed to yield satisfactory values of

small moments because of experimental error.

The aim of the present work has been to employ vapor phase investi-
gation to determine the moments of an assortment of hydrocarbons which
would be expected to have small moments but have either not been reported
or have been reported to be zero, and to re—examine the moments of
l, 4-cyclohexanedione and of a group of 2321' 1, 2-dihalogenocyclohexanes
previously measured in solution and employed in the calculation of iso-
meric energy differences.

The moments of a number of hydrocarbons previously investigated
in the vapor phase are listed in Table I and the previously determined
moments and isomeric energy differences (16, 17, 18) of the substituted

cyclohexanes in Table II.

Table I--Vapor Phase Electric Moments of Hydrocarbons

 

 

====
Compound u Debye Reference
Methane 0 11
Ethane 0 8
O 11
0 10
Propane 0 11
O 11
0. 083 47
n-Butane O 14
Z-Methylpropane O 14
0. 132 46
n-Pentane 0 12
n-Hexane O 9
0 12
n-Heptane 0 9
0 12
Ethylene O 8
PrOpene O. 34 11
0. 35 10
1-Butene 0. 30 14
O. 38 8
trans-Z-Butene 0 14
2-Methy1propene O. 49 14
Acetylene O 11
Propyne O. 72 14
0. 78 15
0. 75 21
l-Butyne 0.80 15
l-Pentyne 0. 86 15
l-Hexyne 0. 89 15
l-Heptyne 0. 87 15

 

Table II--Solution Electric Moments and Isomeric Energy Differences in
Substituted Cyclohexanes

 

 

 

L _= m
A E"
.u o Cal/Mole
Compound Debye T C Benzene CC14 Reference
trans-1, 2-Dibromo-
cyclohexane 2. 14 10 -80 -500 18
2. 13 30
2. 14 50
2. 11 25 -70 -400 19
-70 ~700 17
trans-l-Bromo-Z-
chlorocyclohexane 2. 49 25 370 19
560 -220 17
trans-1, 2-Dichlorocyclo-
hexane 2. 52 30 400 -50 18
2. 50 50
2. 66 40 300 16
2. 67 25 650 19
820 140 17
c_i_s_-1, 2-Dibromo-
cyclohexane 3. 06 25 19
cis-l-bromo-Z-
chlorocyclohexane 3. 16 25 19
cis-1, 2-Dichloro- .
cyclohexane 3. 13 25 19
3. 1 30 18
3 13 25 16
1, 4-Cyclohexanedione 1. 3 25 1900 20

 

3:: _ .
AE - Eax1a1 ' Eequatorial

THEORY

All the material media may be roughly classified, with respect to
their electrical properties, as either conductors or dielectrics. The
former characteristically contain charges, electrons or ions depending
upon the conductor, which are free to move through the conductor under
the influence of an electric field, while the latter generally respond to
an electric field only through polarization mechanisms.

The electrons and nuclei of all molecules are sufficiently mobile
that when a molecule is placed in an electric field a small displacement
occurs between these negative and positive electrical centers creating
an electric dipole. This polarization which is a function of the strength
of the electric field from which it derives may be expressed in vector

notation as;

_I~_>_= X (1)

in which E, the polarization, is the induced dipole moment per unit
volume, 1‘3 is the intensity of the applied. field and X is the electric
susceptibility.

The charge per unit volume of a dielectric due to polarization may
be shown to be - V P. If one takes the total charge enclosed in the
surface of the dielectric to be the sum of the charge, q, on the charged

bodies present, and the polarization charge, then, by Gauss law;

-I§-gg=4w[q-IV-2dT1 . (2)

in which ds is an element of surface and d7 is an element of volume.

. By Gauss' theorem this becomes

Ig-da=4n[q-Ig-_d_s,1

_

from which

IQ; + 4111:) ° ds = 4Trq

The quantity in parenthesis is a vector called the displacement whicih

depends upon the charge, q, only.

1935”“!
P.

= E + 417P (3)

The ratio of the diSplacement to the applied field is constant for
static and low frequency alternating fields for dielectrics at constant

temperature and is called the dielectric constant, e .

D

E: e (4)

Combining this relation with equations (1) and (3) gives:

2=(1+4nX)§ (5)

and
e: 1' + 411 X (6)

The electric intensity inside the region occupied by a single atom
in a dielectric in an electric field may be separated into three parts.
The first part is that due to the applied field, which, if the charge from
which the field derives is immediately adjacent to the surface of the
dielectric or separated from the surface by vacuum only, is equal to

the diaplac ement D.

E=_I_)

The second part is that due to the surface charge of polarization of the

dielectric which may be shown to be:

LE“

= -41TP

The third part is that due to the surface charge of polarization inside

the hypothetical spherical cavity occupied by the atom which is;

i=1"?
3

The effective field in the region occupied by the atom is then;

Eefi = 131+ 3232. + £33

gee = .13 + gm: (7)
3
The polarization, as was stated above is proportional to the field

from which it derives. This relation, in the case of the effective field,
Eeff' requires a new constant of proportionality, a, called the
polarizability.

E= a Eeii (8)

Combining equation (8) with equations (1) and (7) gives

j‘XE =a§ (1+gj‘rX) (9)
3

Combining equation (9) with equation (6) gives;

 

= —na (10)

The polarization, P, which was used in the derivation of this
relation was the total induced dipole moment per unit volume. ' If there

are n individual induced dipoles 2 per unit volume then

 

I: = up (11)
and equation (10) becomes
5 - 1 4
= _ 12
e + Z 3Tr n a ( )

which is the Clausius-Mosotti (22, 23) equation for the induced electronic

and atomic polarization of a dielectric in an electric field.

If the negative electrical center of a molecule does not coincide
with the positive electrical center in the absence of an applied field, the
molecule is said to possess a permanent electric moment. ' In the presence
of an electric field these permanent electric dipoles are influenced away
from the completely random orientation due to thermal agitation and
toward alignment in the direction of the field, giving rise to an orientation
polarization. ‘

Denoting the permanent electric moment of the individual molecular
dipole by E.’ the potential energy of the dipole in the external field is given
by:

U_= 'P-Eeff cos 0 (13)

in which 0 is the angle between the dipole and the field. The average value

of U over the entire sample is given by;

U

 

U: [U expfic-T dU
_U (14)
. —— dU
fexP kT

from which

— _ [cos 6 exp. x cos 0 dcos 6
H _ H Texp. x cos 6 dcos 6

 

in which

X = HEeff
kT

The solution to this equation is known as the "Langevin function" '

(24), and is given by;

IL- : p.(coth x - )

.le

which for most ordinary electric fields reduces to

I; ucoth x
11X
3
- = H2 Eeff
1‘ 3kT

 

(15)

As in Equation 11

E=nh

Substituting this relation into Equation 15 gives

l'U

z nu" Eeif
3kT

which, as in equations (8), (9) and (10) gives

5-1

_ 41rnp.z
6+2 -

__ 16
9kT ( 1
For a dielectric the polarization of which is due to both permanent

and induced dipoles, equations (12) and (16) are combined to give;

6 -1 __ 4 p.
6 + 2 _ 31m (0' +
which is known as the Debye equation (1).

 

(17)

The number of particles per unit volume of a gas at one atmosphere
is given by;

L"; (18)
V

in which N is Avogadro's number and V is the volume of a gram molecular
weight of the gas at the temperature in question. Combining equations
(17) and (18) gives;

5 - 1
6 + 2

 

~_41Ta 411,12 .1_
V‘ 3 + 9R T-

 

PM (19)
If experimental values of the left hand side of equation (19), which

is the total molar polarization, PM, are plotted against the reciprocal

of the absolute temperature the resulting line is straight except in certain
special cases to be treated below

(20)

10

The intercept of this line is Po, the sum of induced atomic and electronic
polarizations,

P0 = PA + PE
while the slope B is the coefficient of the second term on the right and

may be used to calculate the permanent dipole moment, #-

 

4 11
B = 2
9R 1‘
u = 0.0128 x10"18 «l B esu. cm. (21)
. , 4 . .
An approx1mate value of the quantity 3- TI’ (1 may be obtained by sub-
stituting the Maxwell relation;
6 = r2002 (22)

where rpm is the refractive index of the dielectric at infinite wave

length, into Equation 12 (25).
2

_ _1 "’ x 4TTQ A
PE — 71:2 v —————3 A PC (23)
n... + 2

The value of P0 calculated in this way using refractive indices
measured with visible light is in error by the amount of the atomic
polarization. The positions of nuclei are unaffected by light of these
wave lengths with the result that only the electronic polarization, PE,
occurs.

It has been shown (2, 3, 4, 5) that the net permanent electric moment
of a molecule can, in most cases, be considered to be the vector sum of
all of the individual bond dipoles in the molecule, the angles of addition
being simply the appropriate bonding angles. However, when a molecule
is so constructed that bond dipoles may change their directions relative
to one another by rotation about bonds in the molecule, the resultant
net moment may not be so simply treated. In those instances in which

the rotation is perfectly free and all relative orientations equally probable

11

the resultant molecular moment has been shown to be a mean square sum
of the individual bond moments (13). In other instances, when differences
in energy exist between various conformations of the molecule, some
orientations are more probable than others and no uniform relation exists
between the individual bond moments and the net dipole moment, because
the latter changes as temperature variations give rise to redistributions
of the probability between the various conformations of different energy.

The study of the polarization of molecules of the latter type does
not yield a linear relation of that quantity with reciprocal temperature
as predicted by the discussion leading to equation (19), but rather a line
which is slightly curved, and which, consequently, will not yield a unique
value for the dipole moment. Such a study is, however, anything but use-
less, for, since the variation of the moment with temperature is related
to the energy difference between conformational isomers, it may be used
to study this energy difference, a quantity which, for many compounds,
may not be obtained by any other means.

The net electric moment measured for a material composed of two
species having different moments may be expressed, as a first approxi-
mation, by the following expression:

‘2 Z
2 _ n1 $112+ “2 m3
n1 ‘1' n2

 

n; (24)

in which the ni are the numbers of molecules having the moments mi.
The distribution between the two energy levels represented by the mi may

be expressed as the ratio of the Boltzman distribution factors;

ni . -(Ei/RT)

= gle (25)

-E -E
: .g_2‘3.( 2 1)/RT (26)

n1 g1

12

in which the gi are the products of the partition functions and the

degeneracies or statistical weights of the levels, and the Ei are the total

molar energies of the levels. R is the molar Boltzmann constant and T

is the absolute temperature.
Combining these relations yields
“2 _ mi‘ + ae-AE/Rng
l + aemAE/RT
a = i2.
81

which may be rearranged to give

2 z

m - H
-AE = RT 1n —z-——-zl
31H ' m2)

(27)

(28)

from which AE may be calculated from moments measured at specific

temperatures.

EXPERIMENTAL METHODS

Materials

 

Instrument grade (99. 9 mole per cent) 2-methy1pr0pane was obtained
from The Matheson Co. Inc. , Joliet, Illinois. Research grade <3_i_s-2-butene
(99. 3 mole per cent) and w—Z-butene (99. 8 mole per cent) were obtained
from Phillips Petroleum Company. 2-Methylbutane, obtained from K 81. K
Laboratories, Long Island City, New York, was distilled through a fractionat-
ing column of approximately six theoretical plates, dried over metallic
sodium and redistilled. A fresh sample of each material was introduced
into the vacuum system described below, where it was purified to the extent
of removing uncondensable materials by freezing with dry ice and pumping
on the thawing solid.

3-Methy1-1-butyne and 3, 3-dimethyl-1-butyne were synthesized by a
procedure similar to that described by Ivitsky (26) and purified by distil-
lation. These materials were stored in the vacuum system over sodium
sulfate and fractionated there immediately before eaCh run by distillation
between traps.

trans- 1, 2-Dichlorocyclohexane and trans- 1, Z-dibromocyclohexane

 

 

were synthesized by addition of the respective halogen to cyclohexene (27).

trans-l-Bromo-2-chlorocyclohexane was synthesized by bubbling HCl into

 

a. slurry of N-bromosuccinimide, chloroform and cyclohexene (19). All
three materials were purified by vacuum distillation. 1, 4-Cyclohexane-
dione was obtained from K 81 K Laboratories, Long Island City, New York,
and purified by recrystallization from water and benzene.

‘ Ammonia was obtained from Ohio Chemical and Surgical Company.
It was condensed in the system on metallic sodium and further purified

by repeated distillation between traps and by degassing as described above.

13

1'}

14

The physical constants of the experimental materials are given in

Table III.

Dielectric Constant Determination

 

The method employed for the determination of the dielectric constant
depended upon the measurement of the difference in the capacitance of a
condenser alternately filled with a vapor and evacuated. The total capaci-
tance of the condenser and its leads corresponding to each of these

conditions is given respectively by;

CT

Co'l‘Cf

CT CX+ Cf

in which CT is the total capacitance, Cf is the fixed capacitance of the
leads, CO is the capacitance of the condenser only, evacuated, and Cx is
the capacitance of the condenser only, filled with vapor. The difference

in capacitance for these conditions is;
AC : CX " CO.

Substituting the dielectric constant, e, as defined by the expression;

.= Cx

6X __
Co

the change in capacitance is given by;
AC = C0 (EX - 1)

which may be rearranged to give;

6 -1= —— (29)

The quantity AC was measured using ammonia to obtain CO by
equation (29), and again measured using the material under investigation

to obtain 6X by equation (29).

15

Table III--Physical Constants of Subject Materials

 

 

 

 

 

m.p. b.p d.

Compound 0C 0C g ./ml. T7
3-MethY1-1-butyne 29.0 0.6727“? 1 3756?;
3,3-Dimethy1—l-butyne -78.21 37.7 0.667820 1 3736;;
cis-2-Butene -138,9 3_72 0.6350 _____
trans-Z-Butene -105.6 0.94 0.635° .....
Z-Methylpmpane -145.0 -12.2 0.6108’25 1 35143-5
2-Methy1butane -159.6 27.95 0.619720 1 35983
trans-1, 2-dibromo-

cyclohexane -2.5 92.3 1.78425 1 5507;;
trans-2-dichloro-

cyclohexane -6.3 71.1 , 1.1839-20 1 4903
trans-l-bromo-Z-

chlorocyclohexane -18. 77. 1.4.7925 1 5173;;

1, 4-cyclohexanedione 78. ---- -----

 

16

The Capacitanc e C ell

 

The condenser for which AC was measured consisted of five nickel
plated copper cylinders pressed together coaxially using small rectangular
Teflon spacers (32). It was enclosed in a Pyrex glass cell schematically
represented in Figure l. The cell was provided with access to a vapor
handling system and a pressure switch and fitted axially with a deep well
into which a bundle of copper wires was inserted to assist in temperature
equilibration of the enclosed Space.

The innermost, middle and outermost cylinders of the condenser
were connected together by a platinum wire lead silver soldered into the
cylinders. This lead was led to ground by means of a tungsten electrode
sealed through the cell wall. A lead from the two intermediate cylinders
was led through the cell wall in the same way, and connected by means of

a rigid coaxial cable to the measuring circuit.

Capacitanc e M ea sur em ent

 

Since only the values of changes in the capacitance of the cell
corresponding to changes in its condition were required for the calculation,
the method of measurement involved only a means of detecting such changes
and a calibrated means of reversing the effect.

The circuit employed, called a heterodyne-beat circuit, a block
diagram of which is shown in Figure 2, consisted of a balancing or measur-
ing network and a type of beat-note null-point detector.

The balancing network (32), diagramed in Figure 3, consisted of an
arrangement of variable condensers connnected in parallel with the cell.
The capacitance of the network was the sum of the capacitance of the cell
and the total capacitance of the variable branch, so that for a change, AC,
in the capacitance of the cell the capacitance of the network changed by an
equal amount and by an equal and opposite change in the capacitance of the
variable branch, the capacitance of the network was restored to its original

value .

l7

 

 

To material handling
system

A / To pressure switch

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I, ‘3‘
To ground % \"’ ‘To measuring circuit
-1 r
' l
' l
| I
' I
LJ
W N
Teflon \
Spacers \ Nickel plated
fl / copper cylinders
v
1

 

 

 

 

 

Figure 1. The Capacitance Cell

 

18

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ixed
~Frequency
Oscillator
Oscillosc0pe
Mixer 0‘ Frequency
Standard
, Variable
Frequency
Oscillator
1 r ——————————— 1
I l
' 1
l . —- .
' Variable F3611 l Balancmg
. Branch 1 Network
| l I l
I
c.___._ _ ____._____.|

 

Figure 2. Block diagram of heterodyna-beat apparatus.

 

19

 

 

T To detector circuit

 

 

 

c ell l

 

 

 

 

 

 

 

 

 

 

 

 

 

—_l_—

 

Figure 3. The balancing network.

C1 General Radio IOO'IIOOHHf precision variable
condenser Type 722N.

C2 General Radio 10‘-105p+1f decade condenser.
c3 1751...: variable air condenser. '
C4 Primary standard condenser.

C5 335111.11 variable air condenser.

C6 IOuuf ceramic trimmer.

 

20

The null-point detector (32, 33), shown in Figure 4, consisted (of
five elements, a crystal controlled 500 kc oscillator, a variable frequency
oscillator having the measuring network in its tuning circuit, a mixing
circuit in which the signals from the two oscillators were subtracted, a
cathode ray oscillosc0pe, and a reference frequency oscillator employing
an‘American Time Products Inc. type R2003 thermally compensated bi-
metallic fork frequency standard.

The tuning circuit of the variable frequency oscillator was an
inductance-capacitance (L-C) resonant 100p. . The frequency of oscillation
of the resonant loop determined the frequency of the oscillator and was

itself determined by the value of its elements according to the expression;

f = 1 (30)

ZTI'JLC

in which .f is the frequency, L is the inductance and C is the capacitance.

 

Since the inductance, L, was fixed in (value, the frequency of the variable
oscillator depended upon the value of C, which consisted of the measuring
network. A change in the capacitance of the cell was, therefore, detect-
able as a change in the frequency of the oscillator, and restoration of the
original value of the capacitance of the balance network by adjustment of
the variable branch resulted in restoration of the original signal frequency.
The signal from the variable oscillator was combined with that from
the fixed oscillator in the mixing circuit, resulting in a new signal having
a frequency equal to the difference between these two. This signal, which
was subject to some synchronization near the zero beat (equal frequency
setting) was led to the horizontal deflection plates of a cathode ray
oscilloscope while a 400 cycle signal generated by the reference oscillator
was led to the vertical deflection plates. The resulting figure on the
face of the tube was a Lissajous figure which was circular or elliptical

when the mixer signal frequency was 400 cycles.

21

Figure 4.

Capacitors (1111f)

C7, C8, C10, C17 107
C23 10"
C22 2. 5 x 105
C16, C20, C21, C24 105
~ C12 104
C9,C13,C15 5 x103
C11 2. 5 x 103
C18 25
C17 335
C14, C19 50
Resistors (kohm)
R1, R7 20
R2, R3, R26 500
R4, R6, R11, R22 15
R5 25
R8 27
R9 50
R10, R18, R19, R25 47
Miscellaneous
X 500 kilocycle crystal
L 200 (lb.
. RFC Radio-frequency choke

Legend

400 volt electrolytic
25 volt electrolytic

600 volt paper
600 volt paper
600 volt paper
500 volt paper
mica

mica

variable air
ceramic trimmer

R12
R13
R14, R16, R18, R23
R15
R17
R20
R21
R24

7
0.7
100
22
33
0.2
82

22

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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23

It was thus possible, by adjusting the variable. branch of the balance
network to obtain a circular Lissajous figure on the oscilloscope, changing
the condition of the cell, and restoring the original figure by making a
calibrated adjustment of the variable branch, to measure the change in
capacitance corresponding to the change in condition of the cell.

The components of the variable branch of the balance network, which
are listed in the legend of Figure 2, were chosen to' give a calibrated range
of variability of about 1. Suuf with a maximum of linearity. The derivative
of the balancing network with respect to the calibrated precision variable

condenser C1, is:

dill : C32 (31)
dCl (C1+ C2 + C3)2

 

It is apparent from this equation that for large values of C2 the curve is
substantially linear and that the range of variability is to a large extent
a matter of choice since it may be altered significantly by altering either
C2 or C3 or both.

The scale of the precision variable condenser, C1, which had ten
thousand divisions, was calibrated against the primary standard capacitor,
C4. With C3 set for its maximum value and C2 set for 30, 000uuf this
calibration was;

dCT

__ ,e 88f
dCl — O'COOIS scale div.

The primary standard employed for the calibration (34) had 2600
scale divisions of which only the central 200 were used. The capacitance
change per scale division of this condenser was 0. 001057uuf per scale
division.

All of the circuit elements except the primary standard condenser,
, C4, the oscilloscope and the reference frequency oscillator, which are

temperature compensated, were inclosed in a wooden box lined with

24

grounded c0pper screen as an electrostatic shield. The temperature of

the box was controlled at about 40°C by a sealed mercury thermo-

regulator and thyratron relay. The heating element was a 50 watt
incandescent light bulb. Power for all units except the oscilloscope

was regulated by means of a Stabiline Type 1E5 1002 A.C. voltage regulator

manufactured by The Superior Electric Company, Beverly, Massachusetts.

Temperature Control and Measurement

 

The capacitance cell was suspended by means of a copper frame in
a constant temperature bath which is shown in Figure 5. The bath con-
sisted of a massive cast aluminum cylinder seven inches in diameter with
a hole in its center only slightly larger than necessary to allow insertion
of the cell and its frame. Two spirals of No. 18 Nichrome resistance
wire, separated from the block and from each other by asbestos paper,
were wound around the bath and terminated in ceramic terminals. The
outermost coil was connected directly to a power transformer to be used
as ballast heat at higher temperatures. The innermost coil was connected
to a temperature control circuit.

Temperature regulation was accomplished through a saturable
reactor, the current in which was controlled by the phase sensitive
detector circuit (35) diagramed in Figure 6. The temperature sensing
element was a 100 kohm, 2% thermistor inserted in a small hole drilled
vertically into the wall of the aluminum bath.

. The top of the bath was closed by mounting the pressure switch,
described below, in the ring which served to anchor in place the frame
in which the cell was suspended.

Temperature was measured by means of a copper-constantan
thermocouple, and a Leeds 81 Northrop Model K-2 potentiometer using
National Bureau of Standards conversion data. The reference junction

was a slurry made from solid distilled water in a Waring blender.

25

 

 

To manometer control To manometer control

system system
\ / It

To material
handling system

   

fo?‘

   
  
  
   

To temperature
regulator \

 

 

To temperature

To potentiometer
II" regulator

\

V.v.v.v

To measur 5““

ing/r2“:-

To power
trans-
former

 

  
  

W
"A’Av.v.‘

. ‘V‘v I "v.
AV‘V‘V‘ I '.v:$:€

 

 

 

 

- on
DOC-0": .-

A

.noo-w—
{QII.IUV~V

 

 

 

 

 

 

 

Figure 5. Constant temperature bath.

 

C25, C26, C31, C34
C27, C29

C28, C32, C33, C35
C30

R27, R30, R34
R28, R32, R36, R41
R29

R34, R35, R39, R40
R33

R38

26

Figure 6 . Legend

Capacitors (11f)

Resistors (kohm)

T Thermistor
B Balance resistor
Ratio arm

SR Saturable reactor

0.05

0.25
10.0

0.5

2000

50
1000
500
10

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28

The hot junction of the thermocouple, supported by a double-barrel
ceramic tube was tightly wedged between the wall of the cell and the
cell support frame in such a way that the junction hung in the space
between. Although this arrangement allowed measurement of the
temperature of the bath rather than that of the cell it was found prefer-
able to one in which the thermocouple was placed in the tube in the center
of the cell, because the heat conducted out of that region by the thermo-
couple wires tended to disrupt temperature equilibrium between the
plates and produce drift in the capacitance of the cell.

The entire bath was enclosed in a wooden box 24 inches on each
edge and surrounded by expanded mica insulation.

With this arrangement temperatures at the junction location varied
less than 0. 2°C/hr above 400°C with short range variations of o. 1°C or

less. At lower temperatures control was slightly better.

Pressure Measurement

 

All vapor pressures were measured using an absolute mercury
manometer and cathetometer. The manometer, which was constructed
from 16 mm diameter Pyrex tube, was surrounded by a 5 inch Pyrex
tube closed at both ends by wooden blocks. A thermometer was hung
in the dead air space thus created.

All pressures were reduced to 00C mercury temperature and
corrected for the thermal expansion of the stainless steel scale of the
cathetometer according to the following equation;

P =P-P [ dt-B(t-20)

 

] (32)

O 1 at
in which
0
PO - pressure reduced to 0 C mercury temperature
P = observed pressure
. . 0
t = ambient pressure in C

29

1. 818 x 10‘4c,m3/0C cubical coefficient of
expansion of mercury

9
ll

0 . . . .
10 x 10'6cm/ C linear coeff1c1ent of expansmn
of stainless steel scale

‘CD
ll

Pressure measurements involving the hydrocarbon series were
made with the manometer open to the system and the vapors in direct
contact with the mercury column. The substituted Cyclohexanes,
however, were rather involatile and required constant application of
heat to create sufficient vapor pressure for the measurement.

In handling the latter materials the cell and vapor handling unit were
isolated from the rest of the system to prevent condensation of the
vapors, and pressures were transmitted by the pressure switch and
manometer control system to the manometer where they were measured
in the usual way.

. The pressure switch, which is shown schematically in Figure 7
(36), consisted of a circular nickel diaphragmwelded at its periphery
between two circular half- shells of nickel clad steel, and surmounted
at its center with a silver plated copper contact. The upper half— shell
was fitted at its center with another silver plated contact well insulated
electrically from the half— shell, and adjustable in height. COpper tubes
issued from the enclosed spaces formed by the two half- shells, the
lower one being sealed into the cell using aaKovar glass to metal seal
and the upper one leading to the manometer control system.

-The manometer control system which is shown in Figure 8 con-
sisted of a vacuum pump separated from the manometer and pressure
switch by a needle valve, a venting system for the manometer and
pressure switch consisting of a hypodermic needle with its point ground
off butted against the rubber faced armature bar of a relay, and circuitry
for actuating the relay upon the closing of the two contacts of the pressure

switch.

30

 

 

 

 

szumofiimoowrr

, Figure 7. The pressure switch.

Teflon gasket

Bakelite insulators

Fiber insulation

Teflon packing

Gland

Air balancing connection

Diaphragm case made from nickel clad steel
Nickel

Steel

. 003 inch Nickel diaphragm

Proces s gas connection

- Adjustable contact

 

 

31

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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To cell TC-l 117. NGT
V\ S -l—
N ' 19.25
g To manometer . O i
To pump

110 V AC

 

Figure 8. The manometer control system.

Plate relay
Blunt hypodermic needle
Rubber faced armature bar of P
11-inch coil spring
Two filament transformers wired in series
-1 1 megohm i— watt
2 15 kilohms ;- watt
-3 250 ohms 10 watt
1 0. 008 (if

owww~m<z¥u

 

32

In operation the vacuum pump, working through the needle valve,
reduced the pressure in the control system until it was slightly less
than that in the cell. The pressure switch contacts'then closed,
actuating the relay, drawing the armature bar away from the vent
and allowing the pressure in the system to increase until it was equal
to or slightly greater than that in the cell. The pressure differential
then opened the contacts allowing the vent to close. This cycle repeated
itself at small intervals during operation of the apparatus, holding the
mercury level in the manometer practically constant.

The pressure indicated by the manometer when the transmitter
was in use was subject to some variation over a wide range of pressures,
the variation being greater or less depending upon the adjustment of
the movable contact in the pressure switch. These variations were
charted at each temperature at which the transmitter was used and

appropriate corrections made to experimental readings.

The Materials Handling System

 

A vacuum system constructed from Pyrex tube, schematically
diagramed in Figure 9, was used for purification, handling and storage
of materials. The upper half of the system was used with subject
materials and the lower half was used with ammonia. . The system was
provided with access to a Kontes Glass Company Type-A McLeod-
‘Lippincott gauge having a range of 0. 001 to l. 0 mm Hg and to a series
of four drying tubes containing, variously, NaZO, CaSO4‘ and Mg(‘ClO4)z.

Two interchangeable parts were made for the link which connected
the cell to the system. One of these, shown attached to the system,
was used with the hydrocarbons and the other, shown in the box, was

used with the substituted cyclohexanes.

33

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PROCEDURES

Preliminary to making a series of measurements it was frequently
found necessary to remove all T-bore stopcocks in the system, clean
both the plug and the barrel with a mixture of petroleum ether and chloro-
form and regrease them. The grease used for this purpose was Dow
Chemical Company High Vacuum Stopcock Grease: Twice during the
period in which the system was in use it was cleaned throughout using

a mixture of 20 m1. of 50% aqueous KOH and 80 ml. of ethyl alcohol.

 

Constant Temperature Bath

Adjustment of the bath temperature was always carried out at least
eight hours in advance of its anticipated use to allow complete temperature
equilibration of the components of the cell. Adjustment was made, with
the detector in place, by setting the ratio and the balance controls of the
Wheatstone bridge of which the detector is the unknown arm. Balance of
the thermistor resistance at its temperature was detected by a gradual in-
Crease in the milliammeter reading as the ratio potentiometer was
advanced from zero, terminated by a sharp drop in this reading when the
balance point was reached. Further advance of the ratio potentiometer
resulted in another more gradual increase in the milliammeter reading
usually terminated by the destruction of the thermistor, the symptom of
which was the complete absence of a drop in the reading as the ratio
potentiometer was advanced from zero through the scale. At this point
it might be well to note that condenser C30 may be destroyed by too
great an instantaneous unbalance in the bridge. The symptom for this
difficulty was maximum current through the milliammeter regardless

of control settings .

34

35

The procedure for the temperature adjustment was as follows:

1. With saturable reactor set for manual control, and its power-
stat set at some relatively high value, and the booster
powerstat on and set at about 75 volts, the bath was allowed

to heat and its progress followed using the thermocouple.

2. When the thermocouple registered a temperature about 150

less than that desired both powerstats were turned off.

3. When thermocouple readings leveled off the balance point of
the controller was located, starting with the largest balance
resistor, by advancing the ratio potentiometer from zero.
Progressively smaller values of the balance resistance were
then substituted to bring the balance point near the center of

the ratio potentiometer scale.

4. A setting of the saturable reactor powerstat was chosen which
would require that about 2milliamperes of current flow to

maintain the balance temperature.

5. If sufficient power could not be taken from the saturable
reactor a small amount of power was added from the booster.
_ This amount never exceeded 25 volts, however, even at

temperatures above 200°C .

6. If the temperature established in this way was not satisfactory,
the ratio was adjusted in the appropriate direction to provide

more or less power at balance.

It was found that the temperature could be changed by about 35°C

by changing the balance resistance one scale unit with no change in ratio.

36

Measurements

 

The procedure for finding the Lissajous figure consisted of
evacuating the cell, setting the precision variable condenser to a value
about 100 divisions below its upper limit and tuning using C4 until the
circular figure was located and its rotation almost stopped. The figure
was then stopped with either C5 or C6. In routine practice it was not
necessary to readjust C5 although the figure had frequently to be adjusted
using C4 or C6 to compensate for drift in oscillator frequencies, which
was almost always present to a greater or less degree.

The drift mentioned here derived from two sources; changes in
ambient conditions resulting in changes in the values of the many air
condensers in the circuits, and changes taking place in the cell as a
result of the cooling of the plates by the subject gase s.. In order to
cancel the effects of these changes upon the measurement a procedure
was adopted which consisted of making sets of eight or more capacitance-
pressure measurements with alternate measurements corresponding to
reverse changes in condition. Thus,a measurement of_AC and AP for a
pressure reduction was followed after a fixed equilibration period by a
measurement of AC and AP for a similar pressure increase. This was
followed after the same equilibration period by a repetition of the first
measurement and so forth.

The procedure for making the measurement consisted of allow-
ing the vapor to evaporate from the trap in which it was condensed,
usually the one nearest the cell, until a pressure of about-i— atmosphere
was attained. After the equilibration period capacitance and pressure
were recorded and vapor was withdrawn by condensing in one of the
traps until the pressure was reduced to about 100 mm. The equilibration
period was again observed and readings made, following which the

. . 3
pressure was increased again to about 4 atmOSphere. Temperature was

37

recorded about every half hour or when a significant change took place.
It was usually checked during every equilibration period.

The pressure range used was chosen to avoid the adsorbtive
effects which were shown to occur at low pressures and minimize the

effects of non-idealities of the gases at higher pressures.

Low Boiling Materials

 

The procedures described below are typical of those employed
in measurements involving ammonia, which was used for obtaining the
cell constant, as well as those involving the subject materials.

The usual procedure for handling the hydrocarbon materials was
to introduce them into the system by condensing them in the trap fitted
for this purpose and degassing them as described in the section on
materials. The lighter materials were introduced into the system
studied and discarded while the acetylenes were stored in the system
permanently. The material being studied was condensed in the trap
nearest the cell in sufficient quantity to last the experiment and evaporated
into the cell as occasion demanded. Withdrawals were made by condens-
ing the vapor in the appropriate trap on the manifold.

At the end of a run with one of the materials the parts of the
system which had been used were completely evacuated and washed
several times with dry air. Before the next compound was studied the

system was washed with its vapors.

High Boiling Materials

 

The procedures practiced in making the measurements on substi-
tuted cyclohexanes differed primarily in the handling of the materials.
' Small quantities of the materials were introduced into the heating
flask which was substituted for the trap nearest the cell. The sample

was degassed and the flask and cell isolated from the vacuum system,

38

and pressure and capacitance were recorded. The entry tube to the
cell was heated to 170°C with a heating tape and the flask was heated
by a sand bath held at 1650C. Heating was continued until pressure
equilibrium was attained,and pressure and capacitance were read
immediately. The sand bath was then removed and a dry ice bath
substituted to condense the vapors. An equilibration time was allowed
which corresponded to the time necessary for the pressure build up,
and pressure and capacitance were again measured. This pr6cedure
was repeated several times with fresh samples of each material.
Pressures of these vapors were 'measured by means of the
pressure transmitter. The necessary plot of variation between trans-
mitted pressure and true pressure was made before the measurements
at each temperature by introducing dry air into the system and measur-
ing its pressure directly and by transmission. If the variations
determined in this way were large, the height of the movable contact of

the pressure switch was adjusted and variations again plotted.

DATA AND CALCULATIONS

The following pages contain tabulated capacitance, pressure,
and temperature data for the ten compounds studied and calculations
leading to the molar polarization, PM, at each temperature. Plots of
PM as a function of the reciprocal temperature are also presented
although the sloPes and intercepts of these lines were determined by
the method of least squares for the purpose of calculating the results.

As was mentioned above, pressure-capacitance data was taken
in sets of eight or more measurements in alternate directions of change
at each temperature. The ratio of the average capacitance change in
1111f to the average corrected pressure change in mm, dC/dP, was con-
verted to AC, the capacitance change per atmosphere. AC was then

used with the cell constant to calculate the quantity (6-1) by Equation 29.

The Cell Constant and the Dielectric
Constant of Ammonia

 

 

Capacitance-pressure data was taken for ammonia at each
temperature and converted to AC as above. This value was then used
with the appropriate dielectric constant to calculate CO by Equation 29.
The dielectric constants of ammonia were calculated at several
temperatures by the Debye equation using published dipole moment and
Po values (28, 29, 30), and molar volumes calculated from the following

equation of state (31).

RT 7
=—+B+——-
V P RT

(33)

625 0.494 x 108
13:2.36x10-3-—T—z — T,

 

. . 16
7=-259.1x.1o-6+§Qf§_§_3 035;: o

 

39

40

The calculated dielectric constants were plotted as a function of
temperature on a large graph from which the value corresponding to any
temperature could be taken. The data for this plot as well as corres-

ponding values of the molar volume are tabulated in Table IV.

Molar Volumes and Molar Polarization

 

The total molar polarization in the form of the Debye equation

expressed by Equation 19;

requires the molar volume at one atmosphere of pressure at each
temperature at which the calculation is to be made. These were calcu-

lated using Van derWaalsl equation
V3 - (b + RT)/V’2 + aV— ab=0

The parameters, a and b, which are listed in Table V, were estimated

from critical constants using the following expressibns

27R7‘T:
: —— (34)
64pC
RT _
b: 815—;— (35)
C

When critical data were unavailable the parameters were estimated

by structural analogy with compounds for which critical data were

available (37) .

Molar Refractions

 

Since the dipole moments of the substituted cyclohexanes were
expected to vary, they were determined for each molar polarization

value by calculating PE by equation 23, and using the equation

41

>’.<
Table IV--Calculated Dielectric Constants of Ammonia

 

O

 

T, C ’1? 1 -(5-l)x10°
300 24.60 6000
310 25.43 5639
320 26.25 5311
330 27.07 5013
340 27.89 4735
350 28.71 4489
360 29.53 4257
370 30.36 4043
380 31.18 3845
390 32.00 3664
400 32.82 3496
410 33.64 3337
420 34.46 3192
430 35.28 3054
440 36.10 2928
460 37.74 2694
480 39.39 2495
500 41.03 2312

 

::<
At one atmOSphere pressure.

42

Table V--Van derWaalS‘ Constants

 

 

t ====
Compound a 17: atm. b 1. mole"1 Reference
mole"z

2-Methylpropane 12. 9 0. 11 37
2-Methy1butane l8. 1 0. 14 37
cis-Z-Butene 12.8 0.11 38
trans- Z-Butene 12. 9 0.11 38
3—Methy1-1-butyne 13.4 0.11
3, 3-Dimethy1-1-butyne 16. 5 0.12
trans- 1, 2-Dibromo-

cyclohexane 30. 87 0. 17
trans- l-Bromo-Z-

chlorocyclohexane 31. 88 0. 18
trans-1, 2-Dichloro

cyclohexane 33. 33 0. l9
1, 4~Cyclohexanedione 32. 32 0. l6

 

43

 

p. = 0.0128 N/(PM - PE)T (36)

3,, - 1
a, + 2
refraction was calculated by summation of refraction equivalents for

The quantity T1 V, which is referred to as the molar

the sodium D line of the various atoms in the molecule (13).

Dipole Moments and Distortion Polarizations

 

The slopes and intercepts of the PM vs l/T plots for hydrocarbon
vapors were calculated by the method of least squares which provides
parameters for the line yielding the minimum squared deviation of the
points from the line. The parameters were calculated using the follow-

ing relations;

PM = y 1/T = x
y = a + bx
a. = Na b 2 Nb
D "13"
Na = Zyi Ex: - ExiExiyi
i 1 i i
Nb= n ifxwi - fivfixi

D

nEx? - 2-2
11 (1x1)

Dipole moments of the hydrocarbons were calculated by Equation
20 using slopes obtained in this way while those. of the substituted cyclo-
hexanes were calculated by the same equation using slopes derived from
single experimental points and the molar refraction.

Energy differences between conformational isomers of the various

substituted cyclohexanes were calculated using Equation 27.

44

Table VI--Capacitance-Pressure Data for 2-Methy1propane

 

 

 

 

 

 

 

a I =====
dC 1111f dP mm dC‘ 1111f dP mm dC 1111f dP mm
T = 451. 38°K T = 425.08°K T = 385.13°K

(cont.) (cont.)
0.076 106.03 0.082 101.48 0.301 352.43
0.080 108.07 0 076 98.30 0.319, 371.46
0.082 108.81 0.079 97.70 0.331 375.64
0 080 108 07 0.085 102.98 0.346 392.82
0.078 110.95 0.083 106.11 0.321 382.86
0.118 160.36 1.517 1934.26 0.319 363.67
0.078 107.52 3.829 4409.14
0. 070 107. 32 dC/dP = 0.784 x10'3
0.083 107.27 dC/dP = 0.868 x10'3
0.072 99.90
0.070 103.39
0.118 157.42 'T==405.720K
0.072 97.66 T = 367.39°K
0.076 105.43 0.271 327.75
0.081 104.83 0.284 340.45 0.340 365.92
0.077 102.69 0.272 344.83 0.339 368.01
0.087 117.63 0.277 327.35 0.352 380.76
0.084 116.78 0.257 318.74 0.351 381.60
1.482 2030.13 0.268 327.25 0.353 378.86
0.273 332.56 0.332 375.68
dc/dr>= 0.7303(10‘3 0.258 312.45 0.352 381.95
0 257 312.15 0 353 381.15
0.230 267.52 0.345 372.99
0.219 267.87 0.334 370.70
'T==425.080K1 0.290 352.04 0.361 376.37
3.156 3829.96 3.812 4133.99

0.069 96.13
0.074 91.40 dC/dP = 0.824 x10"3 dC/dP = 0.922 x10"3
0.084 , 106.13

.0.084 105.63
0.079 102.20
0.088 108. 32 T = 385.13°K T = 350.56°K
0.110 159.74 '
0.079 102.43
0.077 98.84 .
0.079 100.34
0.078 98.54
0.080 100.44
0.131 157.55

.318 364.40
.314 358.77
.303 358.37
.319 366.64
.330 371.32
.308 350.76

.358 386.38
.358 378.47
.358 366.82
.361 377.92
.373 379.96
.357 365.27

OOOOOO
OOOOOO

 

45

Table VI - Continued

 

 

 

dC 1111f dP mm dC 1111f dP mm dC 1111f dP mm
T = 350.56°K T = 335.67°K T = 320.06°K
(cont.) (cont.)
0.360 372.49 0.371 367.01 0.384 352.83
0.371 382.00 0.366 362.98 0.352 342.32
0.351 359.10 0.369 362.43 0.377 348.64
0.350 361.64 0.366 362.23 0.371 350.29
0.350 364.97 0.383 378.27 0.371 354.22
3.947 4095.02 0.390 375.43 0.398 365.22
0.393 390.11 0.378 357.81
dC/dr>= 0.964rt10'3 0.399 392.21 0.381 354.96
0.372 361.93 0.382 354.06
0.359 355.61 0.369 349.24
4.469 4418.78 0.396 364.63
T‘z 335.67°K; 0.394 372.94
dC/dP>= 1.011x10'3 4.553 4267.16
0.353 347.99
0. 348 362.58 dC/dP = 1.067 x10"3

 

Table VII--Molar Polarization Data for 2-Methylpr0pane.

 

 

T AC 10°x (as-1) 106x(—§1—1)— ’17 Pm 103x 1/T

oK puf/atm (6+2) cc/mole cc/mole (0K)”l
451.38 0.5548 1643 547.4 36770 20.13 2.215
425.08 0.5958 1746 581.9 34600 20.13 2.353
405.72 0.6262 1852 617.0 33000 20.36 2.465
385.13 0.6597 1952 650.2 31280 20.34 2.597
367. 39 0. 7007 2048 682. 2 29820 20. 34 2. 722
350.56 0.7326 2142 713.5 28420 20.28 2.853
335.67 0.7684 2246 748. 1 27180 20.33 2.979
320.06 0.8033 2348 782.1 25870 20.23 3.124

 

cc
mole

 

46

 

21—1—

 

 

 

 

1 1 1 1 1 1 1 1 1
2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.
1/T0Kx103
Figure 10. Molar polarization versus the reciprocal of the

absolute temperature for 2-methylpropane.

47

Table VIII--Capacitance-Pres sure Data for 2-Methy1butane

. d
.7

dC 1111f

-
4

dP’nun

dC uuf

dP’nun

dP’nun

 

 

T = 452.69°K

OOOOOOOOOOOOOOOO

.096
.092
.110
.107
.088
.178
.085
.104
.100
.088
.100
.096
.089
.091
.087
.087

 

H

.598

105.
114.
.65
109.
107.
104.
199.
100.
107.
105.

98.
105.
101.
100.
104.

88.

112

23
69

71
52
33
15
45
22
28
70
23
09
84
98
89

1765.

96

dC/dP = 0. 905 x

T = 425. 34°K
0.104 100
0.097 98.
0.096 105.
0.104 104.
0.098 95.
0.095 95.
0.047 47
0.099 110
0.099 109.
0.108 113

.29

49
76
32
11
01

.80
.00

35

.98

10'3

T = 425. 34°K
(cont.)
.102 105.57
.150 149.34
.095 93.66
.095 94.26
. 095 96. 75
.098 99.64
.104 103.67

OOOOOOO

 

1.686 1723.00

dC/dP = 0.973 x

T = 405.68°K

 

0.331 325.92
0.334 324.13
0.317 319.90
0.323 314.22
0.320 316.33
0.316 312.30
0.307 303.24
0.310 311.55
0.364 351.63
0.339 336.84
3.261 3216.06

dC/dP = 1. 014 x

T = 385.09°K

0.331 317.18

10-3

10'3

 

dC uuf
T = 385.09°K
(cont.)
0.423 388.
0. 398 374.
0.401 369.
0.387 360.
0.357 337.
0. 366 346.
0.254 237
0.281 267.
0.369 343.
0. 360 333.
0. 324 299.
4.251 3976.

T = 367. 36°K

.356
.395
.385
.388
.389
.386
.386
.386
.398
.384
.396
.249

OOOOOOOOOOO

 

A.

317.
346.
339.
340.
340.
337.
339.
343.
342.
342.
340.

3730.

54
40
57
80
79
76

.79

12
97
51
50
93

dC/dP = 1. 069 x

64
27
10
20
70
36
50
74
69
69
55
39

10'3

dC/dP = 1.139 x10"3

 

48

Table VIII - Continued

 

i m

dC p.111 dP mm dC 1111f

dP mm dP mm

dC uuf

 

T = 350.53°K T = 335.73°K T = 320.03°K

 

0.432 361.41 0.413 330.82 0.452 343.42
0.417 336.86 0.408 328.18 0.443 335.25
0.454 384.32 0.412 331.77 0.430 327.53
0.472 392.13 0.402 323.95 0.434 335.70
0.434 382.78 0.411 329.78 0.443 333.91
0.462 372.32 0.414 331.12 0.423 325.29
0.407 352.41 0.408 326.54 0.546 422.62
0.446 370.98 0.415 334.90 0.544 407.24
0.381 318.46 0.425 338.98 0.402 311.70
0.386 326.42 0.414 332.26 0.433 .330.07
0.490 407.08 0.412 334.06 0.541 408.04
0.497 395.23 0.418 335.25 0.519 '398.13
. 5.278 4400.40 4.952 3977.61 5.610 4278.90

dC/dP = 1.199 x10'3 dC/dP = 1.245 x 10-3 dC/dP = 1.131 x 10'3

 

Table IX--Molar Polarization Data for 2-Methy1butane

 

 

ll

 

 

 

AC ’17 PM 103 x 1/T
T°K upf/atm 106x(e-l) 106x 2:;2 cc/mole cc/mole (0K)"l
425.69 0.6878 2037 678.5 36780 24.96 2.209
425.34 0.7395 2167 721.8 34410 24.84 2.351
405.68 0.7706 2279 759.1 32860 24.94 2.465
385.09 0.8124 2404 800.8 31140 24.94 2.597
367.36 0.8656 2530 842.6 29670 25.00 2.722
350.53 0.9112 2664 887.2 28260 25.07 2.852
335.72 0.9462. 2766 921.2 27020 24.89 2.979
320.03 0.9964 2913 970.1 25700 24.93 3.125

 

49

 

 

 

 

 

 

26 r
1_
'— 0
25—1: 0
e "r' 0
PM 1— O
0
cc _.
mole
l l l l l l l I
24 T

l
T l l T I l T l
2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1.3.2

1/T°K x 103

Figure 11. Molar polarization versus the reciprocal of
the absolute temperature for 2-methy1butane.

50

Table X--Capacitance-Pressure Data for cis-2-Butene

 

 

 

 

 

 

dC uuf dP mm dC uuf dP mm dC uuf dP mm
T = 451.66°K T = 425. 26°K T = 384.13° K
(cont.)
0 072 98.21 0.081 97.20 0.320 357.18
0.071 102.89 0.082 98.35 0.322 353.44
0.079 105.62 0.084 100.98 0.342 365.59
0.078 102.39 0.087 103.08 0.319 353.79
*0.073 101.49 0.090 107.86 0.319 352.20
0.068 99.10 0.084 102.03 0.342 376.35
0.101 143.71 0.079 99.34 0.339 371.47
0.080 104.79 0.086 105.27 0.335 370.97
0.081 108.30 0.083 102.58 0.345 379.89
0.078 99.69 0 079 96.30 0.347 383.14
0.074 100.64 0.079 99.29 0.334 378.29
0.073 101.58 1.579 1889.63 0.321 342.89
0.115 151.13 3.985 4385.20
0.088 113.28 dC/dp = 0.836 x10'3
0. 090 115. 28 dC/dP = 0.909 x10"3
0 076 96.85
0.071 92.62
0.073 95.06 T = 405.76°K
1.441 1932.63 T‘z 367.75°K:
0.303 348.98
dc/dr>= 0.7463(10'3 0.284 330.37 0.349 359.45
0.310 361.10 0.338 352.33
0.320 367.10 0.323 339.13
0.313 362.25 0.322 338.13
1?: 425.26°K: 0.305 356.72 0.331 340.66
0.299 347.80 0.324 350.27
0.091 104.47 0.313 367.73 0.339 334.79
0.088 106.56 0.316 365.53 0.319 356.70
0.092 104.32 0.303 352.88 0.356 366.75
0.089 104.47 0.302 352.13 0.366 357.64
0.092 105.57 0.306 358.41 0.329 357.44
0.085 101.13 3.674 4280.04 0.338 358.49
0.128 150.83 4.034 4211.78

dC/dP = 0.858 x 10-3
dC/dP = 0.958 x10"3

 

51

Table X - Continued

 

dC 1111f dP mm dC 1111f dP mm dC 1111f dP mm

 

T = 350.57°K T = 335.69°K T = 319.99°K

 

 

 

0.367 364.80 0.361 357.26 0.401 352.62
0.352 354.74 0.392 366.82 0.383 346.60
0.363 349.56 0.391 365.57 0.400 354.91
0.380 368.63 0.374 349.99 0.392 352.23
0.404 384.57 0.389 353.02 0.386 342.12
0.373 372.32 0.391 363.33 0.380 340.73
0.352 344.33 0.386 357236 0.379 335.80
0.347 351.05 0.371 352.73 0.380 340.88
0.365 368.53 0.387 359.05 0.387 345.76
0.373 364.90 0.382 359.50 0.397 355.61
0.369 358.77 0.375 351.38 0.403 357.90
0.361 365.74 0.374 345.71 0.394 354.12
4.406 4347.94 4.573 4281.72 4.682 4179.29

dC/dP = 1.013 x10"3 dC/dP = 1.068 x 10"3 dC/dP = 1.120 x10"3

 

Table XI--Molar Polarization Data for cis-Z- Butene.

 

 

N

 

AC 1 v 13M 103 x 1 /T

TOK upf/atm 106x(€- 1) 106x (ET-2.) cc/mole cc/mole (OK)-l
451.66 0.5670 1679 559.4 37810 21.15 2.214
405.76 0.6521 1929 642.6 33000 21.21 2.465
385.13 0.6908 2044 680.9 31300 21.31 2.597
367.75 0.7281 2128 708.8 29850 21.16 2.719
350.57 0.7699 2251 749.8 28420 21.31 2.853
335.69 0.8117 2373 790.4 27180 21.48 2.979
319.99 0.8512 2488 828.7 25870 21.44 3.125

 

52

 

22 ‘—

cc
mole

 

l l L
T T T I 771
.7 2.8 2.9 .3.0 3.1 3.2

 

 

 

l
I

2.6 2
l/Ton103

Figure 12. Molar polarization versus the reciprocal of
the absolute temperature for cis-2-butene.

 

53

Table XII--Capacitance-Pressure Data for trans-Z-Butene

 

 

 

 

 

dC uuf dP mm dC 1111f dP mm dC 1111f dP mm
T = 451. 20°K T = 425.03°K T = 385.11°K
(cont.)

0.074 99.60 0.072 99.11 0.306 348.92
0.078 102.04 0.066 87.86 0.320 360.87
0.079 103.48 0.080 102.21 0.320 365.80
0.081 103.33 0.119 153.61 0.319 357.78
0.079 125.77 0 071 98.21 0.321 370.48
0.102 149.00 0 077 106.52 0.315 369.23
0.070 101.29 0.083 105.33 0.317 358.18
0.078 102.49 0.087 112.79 0.301 346.52
0.074 105.33 0.081 104.03 0.318 366.14
0.082 108.69 1.433 1847.75 0.332 373.80
0.065 93.32 0.309 356.93
0.070 93.87 dC/dF>= 0.776x10-3 0.320 354.50
0.086 114.69 3.798 4329.15
0.115 154.13
0.063 85.11 dC/dP = 0.877 x10'3
0.071 94.17 T = 405.78%
0.083 112.45
1.350 1828.76 0.313 375.61

0.296 358.76 T‘2 367.76°K:

dC/dP = 0.738 x10'3 0. 302 358.61
0.317 377.60 0.324 360.70
0.313 375.96 0.330 357.78
0 0.299 360.57 0.333 358.27

1:: 425.03:K 0.306 370.23 0.329 353.60

0.197 231.05 0.355 379.69
0.080 100.52 0.299 349.14 0.355 380.98
0.086 101.81 0.285 344.33 0.257 299.17
0.083 106.44 0.277 348.95 0.254 276.12
0.083 102.61 3 204 3850.81 0.355 379.79
0.077 99.67 0.360 385.16
0.074 96.67 dC/dI>= 0.832x10-3 0.331 356.38
0.075 94.73 0.326 351.85
0.066 90.50 3.909 4219.49
0.073 96.13

dC/dP = 0.926 x10'3

 

Table XII - Continued

54

 

 

 

 

 

===r=

dC 1111f dP mm dC uuf dP mm dC uuf dP mm
T = 350.52°K T = 335.67°K T = 320.07°K

0.355 358.62 0.364 354.54 0.384 357.56
0.357 367.24 0.359 356.98 0.379 363.63
0.370 378.89 0.353 354.39 0.383 359.55
0.363 379.88 0.369 358.78 0.384 349.69
0.353 367.64 0.366 362.11 0.373 352.38
0.368 366.49 0.354 349.81 0.370 344.71
0.343 369.38 0.362 351.80 0.364 339.68
0.355 369.08 0.360 360.42 0.382 364.97
0.371 384.42 0.362 353.54 0.393 365.77
0.360 378.69 0.358 355.24 0.385 353.07
0.368 365.50 0.358 355.84 0.376 356.44
0.363 377.25 0.369 354.94 0.387 365.32
4.326 4473.08 4.334 4268.39 4 560 4272.74

dC/dP = 0.967 x10-3

dC/dP = 1.015 x10"3 dC/dP = 1.067 x10"3

 

Table XIII-~Molar Polarization Data for trans-Z-Butene.

 

 

 

AC 1 ’9’ PM 10%. 1/T

T°K 1111f /atm 10°x(€- l) 106x gig-i;— cc/mole cc/mole (OK)-1
451.20 0.5609 1661 553.4 ~‘ 36760 20.34 2.216
405.78 0.6323 1870 623.0 33000 20.56 2.464
385.11 0.6665 1933 657.2 31290 20.56 2.597
367.76 0.7038 2057 685.2 29850 20.45 2.719
350.52 0.7349 2148 715.5 28410 20.33 2.853
335.67 0.7714 2252 751.1 27180 20.42 2.979
320.07 0.8109 2370 789.4 25880 20.43 3.124

 

55

 

214..

 

cc
mole —

 

20 -1-

 

 

 

J
T
2

l 1 I l l 1
I I
.5 2

l
I I I I I
2.2 2.3 2.4 .6 2.7 2.8 2.9 3.0 3.1

l/T °K x103

Figure 13. Molar polarization versus the reciprocal of
the absolute temperature for trans-2-butene.

 

3.

2

56

Table XIV--Capacitance-Pressure Data for 3-Methy1-l-Butyne

 

 

 

 

 

 

= w
dC uuf dP mm dC 1111f dP mm dC 1111f dP mm
T = 433.50°K T = 381.53°K T = 367.50°K
0.127 101.93 0.158 104.39 0.148 95.17
0.132 106.06 0.135 91.68 0.148 94.72
0.132 106.41 0.151 106.77 0.146 94.92
0.128 104.52 0.144 103.14 0.153 94.67
0.141 114.03 0.144 102.09 0.136 103.68
0.127 101.38 0.142 103.04 0.173 99.95
0.132 105.32 0.144 98.35 0.149 97.51
0.131 105.12 0.143 101.00 0.149 95.30
0.125 99.64 0.149 f 91.10 0.157 101.16
0.127 102.93 1.461 1006.19 0.117 95.33
0.125 100.34 0.158 94.34
1.427 1147.68 dc/dr>= 1.452x10'3 0.146 96.53

0.145 95.54
dC/dP = 1. 243 x10"3 0.139 92.75
0 0.147 97.08
T = 375.70 K 0.149 99.02
0 2.243 1452.44
T7: 411.98 K: 0.591 367.64
0. 558 366.00 dC/dP = 1. 544 x 10'3
0.144 97.38 0.571 356.34
0.122 89.26 0.549 346.83
0.118 97.13 0.554 353.05 0
0.115 97.03 0.551 352.85 T‘= 350.55:K
0.125 97.83 0.575 358.47
0.141 107.29 0 549 346.68 0.633 380.18
0.138 106.79 0.515 337.87 0.575 347.17
0.149 109.18 0.541 335.18 0.481 290.95
0.134 102.26 0.538 335.03 0.502 303.80
0 131 105.69 6.092 3855.94 0.532 320.78
0.130 104.10 0.520 331.71
0.133 103.85 dc/dr>= 1.580x10-3 0.669 ~398.08
1.600 1217.79 0.642 382.75
0.568 343.47
dC/dP = 1. 314 x10“3 0.614 364. 33

 

57

Table XIV -' Continued

 

w

 

 

dC 1111f dP mm dC 1111f dP mm dC 1111f dP mm

T = 350.55°K T = 335.68°K T = 320.03°K
(cont.) (cont.)

0.577 347.00 0.586 336.34 0.677 359.25

0.570 342.47 0.638 366.14 0.618 332.96

6.883 4152.66 0.637 366.44 0.638 342.52

0.590 339.75 0.682 361.24

dC/dP>= 1.657rt10-3 0.591 338.75 0.589 371.93

0.449 258.34 0.581 311.85

0.465 261.63 0.660 352.78

0 6.904 3947.92 0.627 337.74

1‘2 335 68 K 0.626 330.22

dC/dP = 1.749 x10"3 0.622 333.61

0.603 341.47 0.466 251.66

0.581 334.80 0.492 263.06

0.592 335.40 7.228 3894.82

0.589 338.34
0.583 330.52 dC/dP = 1.869 x 10"3

 

Table XV--Molar Polarization Data for 3-Methy1-1-Butyne.

-
—_fl

 

N

 

AC 1 v P 103 x 1/T

TOK upf/atm 10°x( -l) 106x:—:;—2—))- cc/mole cc/gole (0K)-l
433.50 0.9447 2798 931.8 35280 32.87 2.307
411.98 0.9986 2955 984.0 33500 32.96 2.427
381.53 1. 104 3256 1084.0 30970 33.57 2.621
375.70 1.201 3308 1102.0 30490 33.80 2. 662
367.50 1.159 3439 1145.0 29800 34. 12 2.721
350.55 1.259 3680 1225.10 28400 34.79 2.843
335.68 1.329 3885 1293.10 27160 35.12 2.979
320.03 1.420 4151 1382-0 25850 35.73 3. 125

 

58

 

36-—

354%

CC

 

mole

33-1

 

.32 ‘—

I I I I L I I I I

 

 

 

I I I l f I h l
2.2 2.3 2.4 2.5 2.6 '2.7 2.8 .

1/T°K x 103

Figure 14. Molar polarization versus the reciprocal of
the absolute temperature for 3-methy1-1-butyne.

59

Table XVI--Capacitance-Pressure Data for 3, 3-Dimethy1-l-Butyne

dC 1111f

dF’nnni

 

dC 1111f

dF’nmni

dC 1111f

dF’nnni

 

T = 433.98°K

.138
.132
.138
.135
.151
.129
.127
.140
.118
.113
.341

0000000000

 

H

103.
95.
96.
97.

105.
95.
95.
97.
85.
88.

962

57
46
10
80
86
66
81
90
71
74
.61

dC/dP = 1. 393 x

T = 412.10°K

.139
.129
.138
.141
.142
.157
.162
.150
.147
.162
.167
.159
1.793

000000000000

 

97.
88.
87.
89.
95.
106.
109.
104.
95.
109.
107.
104.

78
92
22
76
89
79
93
30
39
18
54
20

10-3

1196

.90

dC/dP = 1.498 x10'3

T : 381.55°K

000000000000000

N

.137
.164
.165
.166
.193
.172
.164
.171
.161
.166
.130
.155
.154
.164

.162

.1;
N
as

86.50
95.77
97.36
102.99
111.25
95.07
101.69
104.78
102.79
99.50
79.12
96.35
96.15
102.33
100.04

1471.69

dC/dP = 1.647 x

T = 375.70°K

0000000000

.626
.658
.622
.603
.631
.619
.614
.601
.590
.606

343.05
366.79
342.80
334.84
345.89
341.61
337.52
327.82
325.83
333.19

10-3

T : 375.70°K

'(cont.)
320.
324.
7.332 4044.32

0.573
0.589

25
73

dC/dP = 1.812 x10"3

T : 367.45°K

.171
.160
.175
.178
.156
.175
.165
.171
.166
.154
.153
.154
.157
.151

.286

00000000000000

N

93.
92.
97.
97.
90.
102.
97.
99.
96.
90.
87.
90.
88.
86.

56
22
60
60
82
63
00
89
23
86
47
21
73
99

1321.

81

dC/dP = 1.741 x

T = 350. 54°K

0.560
0.567
0.560

294.
300.
297.

63
15
81

10-3

 

60

Table XVI - Continued

 

dC 1111f dP mm dC 1111f dP mm dC uuf dP mm

 

 

T = 350.54°K T = 343. 22°K T = 333.45°K
(cont.) ', (cont.) (cont.)
0.548 291.49 0.189 97.78 dC/dr>= 2.000x10-3
0.598 316.18 0.198 102.06
0.661 352.78 0.193 101.31
0.679 357.61 0.210 106.64
0.650 343.47 1.565 816.07 T‘z 320.12°r:
0.658 354.32
0.613 329.28 dc/dr>= 1.918}{10'3 0.719 340.08
0.636 339.83 0.704 339.08
0.562 303.14 0.672 318.91
7.292 3880.69 0 0.672 317.32
T“: 333.45:K 0.729 343.72
dC/dP = 1.879 x10’3 0.661 312.95
0.201 101.68 0.659 311.10
0.188 94.86 0.692 328.78
0 0.207 104.47 0.720 338.49
1?: 343.22:K 0.167 83.59 0.754 353.67
0.196 103.35 0.185 90.70 0.761 356.76
0 196 103.30 0.193 97.43 0.721 .336.85
0.197 103.35 0.208 101.36 8.464 3997.71

 

.556 777.91

1...:

0.186 98.28
dC/dP = 2.117 x10‘3

 

61

Table XVII--Molar Polarization Data for 3, 3-Dimethy1-l-butyne.

 

~

 

0 AC (01) v PM 103x 1/T

T K uuf/atm 10°x( -l) 10°x(—€—+-_—2-)- cc/mole cc/mole‘ ( K)"l
433.98 1.059 3137 1045 35250 36.84 2.304
412.10 1.139 3371 1122 33420 37.50 2.427
381.55 1. 252 3692 1229 30890 37. 96 2.621
375.70 1. 377 3792 1262 30400 38. 37 2.662
367.45 1. 323 3926 1307 29720 38.84 2.721
350.54 1.428 4174 1389 28290 39. 30 2.853
343.22 1.458 4276 1423 27680" 39.39 2.914
333.45 1.520 4458 1484 26860 39.86 3.000
320.12 1. 609 4703 1565 25750 40. 30 3.124

 

62

 

41

404

39-5

cc
mole

 

38-

37-

 

 

36 I

I I J I I I
I

 

 

‘—

1
I
2.2 213 214 2.5 2.'6 2.7 218 219 3.'0 3.1 3.

1/T°K x 103

Figure 15. Molar polarization versus the reciprocal of the
absolute temperature for 3, 3-dimethy1-1-butyne.

63

*Table XVIII--Capacitance-Pressure Data for 1, 2-Dibromocyclohexane.

 

 

 

 

 

 

dC 1111f dP mm dC 1111f dP mm
T = 448.46°K T = 467.53°K
0.467 122.7 0.461 125.4
0.464 119.7 0.432 119.8
0.459 118.2 0.524 146.6
0.454 115.2 0.494 139.5
0.539 142.0 0.467 128.9
0.501 132.1 0.445 125.9
0.465 122.7 0.505 143.4
0.453 120.4 0.478 137.2
3.802 993.0 3.806 1066.7
dC/dP = 3.820 x 10-3 dC/dP = 3.568 x10'"3

 

Table XIX--Molar Polarization Data for 1, 2-Dibromocyclohexane.

 

 

0 AC (64) ”.7 PM 103x1/T Po
T .K 1111f /atm 10°x-(—€+—Z-)— cc/mole cc/mole (0K)"1 ccmole'l
448.46 2.910 2707 36120 97.78 2.230 43.26

467.53 2.717 2516 37720 94.90 2.139 43.26

 

64

Table XX--Capacitance-Pressure Data for 1-Bromo-2-Chlorocyclohexane.

 

 

 

 

 

======= w
dC 1111f dP mm dC 1111f dP mm
T = 448.46°K T = 467.53°K
1.009 236.1 0.680 178.0
0.988 236.1 0.673 178.0
1.035 240.3 0.673 183.2
1.010 240 3 0.682 183.2
1.046 253.3 0.965 243.8
1.051 253.3 0.959 243.8
0.604 145.9 0.900 237.5
0.606 145 9 0.921 .237 5
7.349 1751.2 6.453 1685.0
dC/dP = 4.196 x10"3 dc/dP = 3.829 x10‘3

 

Table XXI--Molar Polarization Data for 1-Bromo-2-Chlorocyclohexane.

 

M
N

 

AC ( _1) v PM 10%: 1/T Po
TOK puf/atm 106x???” cc/mole cc/mole (0K)‘l ccmole'l
448. 46 3.189 2966 36100 107. 07 2. 230 40. 36

467.53 2.910 2694 37700 101.56 2.139 40.36

 

65

Table XXII--Capacitance-Pressure Data for l, 2-Dichlorocyclohexane.

 

 

dC 1111f

dP mm

dC 1111f

dP mm

 

T = 441.83°K

.703
.702
.733
.728
.776
.775
.844
.824
6.086

0000000

0

283.
283.
309.
309.
323.
323.
329.
329.

2719074"

dC/dP = 2.443 x10-3

NmmJ-‘suir-‘H

2

o
T = 468.22 K

.649
.638
.885
.885
.557
.548
.162

000000

 

4:-

291.1
291.1
405.5
405.5
246.8
246.8

dc/dP = 2. 207 x10"3

 

Table XXIII--Molar Polarization Data for 1, 2-Dichlorocyclohexane.

 

N

 

AC ( _1) v PM 102x l/T PO
TOK 1111f /atm 106x (—:—+—ZT cc/mole cc/mole ( K)"1 cc mole'l
490.25 1.493 1355 39570 53.62 2.040 27.73
468.17 0. 844 1400 37720 52. 81 2.136 27. 73

 

66

Table XXIV--Capacitance-Pressure Data for 1, 4-Cyclohexanedione.

 

 

 

 

dC 1111f dP mm dC uuf dP mm
T = 490. 25°K T = 468.17°K
0.136 75.0 00085 70.9
0.146 75.0 0.072 70.9
0.167 84.7 0.076 59.5
0.172 84.7 0.061 59.5
0.110 53.5 0.084 70.1
0.100 53.5 0.067 70.1
0.111 54.1 0.445 401.0
0.109 54.1

1.051 534.6 dC/dP = 1.110 x10-3

dC/dP = 1.965 x10"3

 

Table XXV--Molecular Polarization Data for l, 4-Cyclohexanedione.

 

 

 

 

 

AC ’17 P 10%. a/T P
0 6 (6'1) M 0 -1 O 1
T K puf/atm 10 x (6+2) cc/mole cc/mole ( K) cc mole'
490.25 1.493 1355 39570 53.62 2.040 27.73

468.17 0.844 1400 37720 52.81 2.136 27.73

 

RESULTS

Dipole moments and values of PO and PE of the hydrocarbons
are givenin Table XXVI. Dipole moments and differences between Ea,
the energy of the isomer having substituents oriented axially to the ring,
and Ee' the energy of the isomer with equatorially oriented substituents

in the substituted cyclohexanes, are listed in Table XXVII.

67

68

Table XXVI--Dipole Moments of Hydrocarbons

=_7 w I

 

 

11. P0 PE *

Compound Debye cc cc

2-Methy1propane 0. 18 19. 74 20. 67
2-Methy1butane 0. 10 24. 78 25. 29
trans-2-Butene 0 20. 44 20.17
cis-Z-Butene 0.24 20.35 20.17
3-Methy1-1-butyne 0. 78 24. 07 23. 29
3, 3-Dimethy1-l-butyne 0.83 27.15 27.91

 

:1:
Calculated by Equation 23.

Table XXVII--Dipole Moments and Isomeric Energy Differences of
Substituted Cyclohexanes

|J. AB: Eaa-Eee
Compound T, °C Debye Cal/mole

 

trans- l, 2-Dibromo

cyclohexane 177 2. 00 -332
196 l. 99 -358
trans- 1, 2-Dichloro-
cyclohexane 170 2. 28 7 102
196 2. 30 152
trans- l-Bromo-Z-chloro—
cyclohexane 196 2. 17 -72
219 2. 21 - 19
1, 4-Cyclohexanedione 196 1. 39 ---

218 1.44 ---

 

ANALYSIS OF ERROR

Uncertainty in the values of 11 calculated by Equation 20 were

determined from the total differential of 11 given by;

1
11 = 0.0128 b7
0.0064 db
9111 =—1-—
b2—

in which b is the SIOpe, defined in the case of the hydrocarbons as;

0.4
II
I

1:
‘0

Z

Z

The differential of the slope is
db = ——"z——
du = dPM - dPi/I
1
dV: (— z- 1112) 9T

1 1 1 1 1 1
db = (E ‘ E11) (9PM ' dPM) ' (PM-PM) (3.7." T2) dT

(T - T,)

Taking the twoA PM as equal and maximizing the term gives

20 P 1 1
_ —-—M— - — - .—
T T'

for the uncertainty of the lepe and

69

7O

. 1 1
000064 2 6PM + (PM-PM) (T2 - T92) 6T (37)
‘5“: ‘T— 1 1
b?- (71" "W

for the uncertainty of u.

The quantity 6? was determined by recalculating values of PM

M
using the equations used for the original calculations, and values
altered by the amount of the experimental uncertainty in the appropriate
direction to yield the greatest change in PM.

Uncertainty in the values of ( e -1)NH3 consists of possible
systematic error resulting from the use of erroneous values of u and
P0 in the calculation and random error associated with the determination

of values of ( from the plot.

6 -1)NH3

The first of these was shown to be negligible by comparing values
of the cell constant measured using ammonia, carbon dioxide and sulfur
dioxide. The second was judged on the basis of the smallest increment

which could be read, to be not more than
- = + 3 10‘6
6 (€ 1)NH3 _ X

Error in the value of AC depended upon the 'precision with which
the capacitance and pressure could be read, and, to a somewhat greater
extent, upon drift of the apparatus. Since the latter source of error
does not lend itself to arbitrary analysis, deviations from the mean
dC/dP for each of the hydrocarbons and ammonia at each temperature
were averaged to obtain an experimental value for the overall uncertainty

of (SAC. This value is;
6 ACNH3= 6 ACK = j; 0. Oluuf/atm
Using these values and data taken at the median temperatures,
the uncertainty in the cell constant was found to be

71

Error in the determination of V resulting from the use of inexact
values of Vander Waal's parameters has little effect upon the value of
the dipole moment because approximately the same correction is applied
to each value of PM and the whole line is lowered relatively uniformly.
Thus a difference of about 0. 5% of the volume occurred between
corrections, amounting to over 1% of the volume, calculated at the
extremes of temperature for Z-methylbutane. This correSponds to a
contribution of less than 0. 05% of the volume by a given molar volume.
Assuming that this increment is in error by not more than 50%, the
value of V was taken as 0.03%.

Values of <5 u for the hydrocarbons calculated using these values
are listed in Table XXVIII.

Errors in values of Po derived from the calculated intercept of
PM vs l/T plots are heavily dependent upon the accuracy of molar volume
calculations. In view of the uncertainty associated with determining the
Vander Waal's parameters from critical data the error in P0 is difficult
to estimate. However, the precision may be estimated by differentiat-
ing the total molar polarization expression.

1

PM: poi-b?

dPM = dPO + b(d"1T‘)+-'1f‘ db

Dropping the second term on the right which is insignificant, rearrang-

ing the maximizing gives

0P : 0P (5b

1
o M+7f

Values computed by this method are listed in Table XXVIII.
Dipole moments of the substituted cyclohexanes were calculated,

at each temperature, by the following equation;

72

 

p. = o. 0128 «I T(PM-PO)

in which Po was calculated by Equation 22. The uncertainty in u in

this case is given by;

 

0.0064 [T 6 (PM-P91 + (PM-Po) 6T]
[TmM-POHT

(Sp:

Which, since the uncertainty of Po is indeterminate and the second term

in the numerator is small, becomes;

_ 0. 0064 T6 PM

6+1 .—

 

Mean of values of 6 H calculated at each temperature for each compound
are listed in Table XXVIII.

Uncertainty in values of AE calculated by Equation 28 could only
be estimated because of the indeterminate error in m, and ma. This
estimate was made by the following equation which was derived by

differentiating Equation 28 and assuming 6mi to be zero.

1 1
<5
6AE= ZRTH (mf-pz + “Ami ) ”

Values of 6 AE calculated from mean moments are listed in Table
XXVIII.

It should be noted that the uncertainty in dipole moments as calcu-
lated by Equation 37 increases as the slope of PM vs l/T plot decreases,
regardless of the precision of the measurement. In the case of the
hydrocarbons the resulting values of the uncertainty are unreasonably
large. Thus, Equation 37 predicts that Z-methylpropane might have a
moment as high as 0. 51 D. , and Z-methylbutane a moment of 0. 66 D.

On the other hand a molecule actually having a moment of 0. 65 D. could
not, according to Equation 37, be found to have a value lower than 0. 5

D. if the precision of measurement were the same as that of the present

measurements.

73

Table XXVIII- -'Experimenta1 Error

ll

 

6 u 5 Po 6 AE

Compound Debye cc Cal/mole
Z-Methylpropane :tO. 32 :I:2. 2
Z-Methylbutane :0. 56 i2. 2
cis-Z-Butene i0. 25 3:2. 2
trans-Z-Butene -----
3-Methy1- l-Butyne :hO. 07 :l:2. 1
3, 3-Dimethy1- l-butyne 3:0. 07 :1:2. 2
trans-l, Z-Dibromocyclo-

hexane 5:0. 06 i 80
trans- 1, 2-Dichlorocyclo-

hexane i0.05 i110
trans- l-Bromo-Z-chloro-

cyclohexane i0. 07 5:130
l, 4-Cyclohexanedione :0. 16 -----

 

If it is assumed that the upper limit of uncertainty of a p value
is that value for which the error, as calculated by Equation 37,
includes the u value, then 6 P values may be obtained for the first three
hydrocarbons which seem much more realistic than those listed in

Table XXVIII. These values are as follows:

6 H
2-methylpropane 0. 16
2-methylbutane 0. l9

cis-2-butene 0.15

 

DI SCUSSION OF RESULTS

HYDROCARBONS

 

The electric moments of 2-methy1pr0pane and Z-methylbutane
obtained here are zero within the indicated experimental error.
However, the value obtained for 2-methylpropane is in quite good agree-
ment with one obtained from microwave measurements (46). «Since the
error as calculated by Equation 37 tends to increase without limit as
the slope of the PM vs l/T plot becomes small, it is possible that
values so calculated are excessive and that moments of the order of
0.1 to 0. 2 Debye exists in these molecules.

A rough relation may be established between moments of
2-methylbutane and 2—methylpropane if it is assumed that the butyl
skeleton of 2-methylbutane is in a perfect skew conformation and that

a uniform gradation of C-H bond dipoles, m, occurs such that

> >
mtert.C-H rnsec.C-H rnprim.C—H

and

2( )

mtert.C-H - mprim.C-H: msec.C--H-mprim.C-H

Let the vector bond moments be

Etert.C-H : é
Ell-sec. C-H : 1-3-
I.)

Eprim. C-H :

so that

74

75

The tetrahedrally disposed bonds about the central atom in 2-methy1-
propane may be resolved into two colinear vectors {5: and 2 since, as
a result of the tetrahedral bonding, the resultant of the three I_)_ bond
vectors about each methyl group is another _D_ bond vector lying along
the respective fourth bond. The resultant of these three 12 bond vectors

is in turn a D- bond vector lying along the A bond.

 

2 - M ethylpropane

The 13 and 12 bond vectors are thus anti-parallel (assuming uniformity
of orientation of the bond dipoles) and the moment of Z-methylpropane
is A_-_I_).

The situation in Z-methylbutane is somewhat different because
of the absence of symmetry. However, the two methyl groups at the
ends of the butyl chain have C-C bonds which are parallel, cancelling
their 2 bond vectors and leaving only a2 bond vector and an 5 bond
vector on the second carbon, opposed (by virtue of the stipulation of
the skewed conformation) by two E bond vectors on the third carbon.
The result is a vector on carbon number 2 of value fl making an

angle of 70 degrees with one on carbon number 3 of value B‘-D. Since

 

both of these are equal to one-half (A-D) the moment of Z-methylbutane
is the sum of two vectors at an angle of 70 degrees each equal to one-
half the moment of 2-methy1propane. The value of 2-methy1butane

calculated from this relation is

76

Z-methylbutane u calc. = 0.15 D.
which is in good agreement with the observed value.
The occurrence of electric moments in ethylenic hydrocarbons

is usually explained on the basis of hyperconjugation structures of

type II.

H H H H

\3 /

/ C=C / C7—C\

H CH3 H CH2
H
+
I II
Propene

Since three structures of type 11 may be drawn for propene while only
two may be drawn for l-butene it may be concluded that the contribution
of polar forms is more significant to the resonance hybrid in the case
of propene than in the case of l-butene. : Propene would therefore be
expected to exhibit the larger electric moment, which, indeed, proves

' to be the case (11).

0.35 D.
0.30 D.

Propene u

l- Butene u

In the case of cis 2-butene three structures of type IV and three

 

of type V may be drawn.

H3C\ = /
/ \
H H
‘ III
H+ H+
H3C CH2 CH2 _ CH3
\E—c/ kc—E/
/ / \
H H H H
N v

cis- 2- Butene

 

77

Each of these forms would be expected to result in a dipole moment
about equal to that of propene. If each form made a contribution equal
in importance to the contribution of II to the propene molecule the

electric moment of cis-2-butene would be expected to be somewhat larger

 

than that of propene. The present work has shown it to be equal or
somewhat smaller. By way of explanation of this result, it should be
noted that, to the extent to which these forms contribute, the hybrid
molecule must support negative charges on adjacent carbon atoms. ‘It is
to be expected, therefore, that such forms will play a smaller role in
the 2-butenes than in propene. Further indications of the importance of
this effect may be had from consideration of the moment of 2-methy1-
propene which has the same number and type of resonance structures

(VI, VII,VIII) as cis-Z-butene;

 

 

H\ — CH 3
C—C
/
H CH3
VI
H+
H CH H CH
3 / Z \T. / 3
C C C C
H CH3 H CH2
VII VIII

but which has only one negative charge site. , The'moment of this
compound is 0. 49 D. (14), which is in agreement with the expected
value of about 0. 6 Debye.

The trans-Z-butene molecule has a center of symmetry and as a

 

result would be expected to have a zero net moment, which the present

work has shown to be the case.

78

The moments of 3-methy1-1-butyne and 3, 3-dimethyl-l-butyne
are somewhat lower than was anticipated in view of the values reported
by Krieger and Wenzke (15) for other mono-acetylenes. It should be
noted, however, that these authors in effect forced the PM vs l/T plots
to intercept the PM axis at the calculated value of the molar refraction.
This procedure ignores the atomic polarization, which increases with
the number of C-C and C-H bonds, and, consequently, leads to results
which are increasingly in error on the high side as the molecular weight
increases.

The direction of the variation of the electric moments in 3-methy1-
l-butyne and 3, 3-dimethyl-1-butyne may be explained on the basis of
either hyperconjugative effects or dipole induced-dipole interactions if
it is assumed for both arguments that the principal bond moment in the

molecule is in the acetylenic C-H bond.

H—+——>C_=—=—C

VI'

R

 

On the basis of hyperconjugation three forms such as VIII' may be
drawn for this molecule while only one such form may be drawn for
3-methy1- l-butyne and none may be drawn for 3, 3-dimethy1-1-butyne.

3". H+
c: cziaz

 

n

H C

 

 

 

c: —-—————(3}{3 ll
\fII' \IIII'

The moment resulting from forms such as VIII' Opposes that
resulting from VI} and, because of the greater number of such forms
which may be drawn for propyne, the moment of that molecule, which
has been reported to be about 0.74 D. (14, 21), would be expected to be
smaller than that of either 3-methy1-1-butyne or 3, 3-dimethyl-l-butyne.

Similarly the moment of 3-methyl-1-butyne would be expected to be

79

smaller than that of 3, 3-dimethyl- l-butyne. In both cases the experi-
mental moments vary in the expected direction.

Shifting now to consideration of induced dipoles, it may be argued
that any contribution to the permanent electric dipole resulting from
polarization of the alkyl groups of these molecules by the field of the
principal dipole would be in the same direction as that dipole and would
result in an increase in the total .moment.. A rough calculation of such
a contribution may be made by assuming that the contribution of the
principal dipole is the same in each case, that is, that its value and
field are the same in each case. The group polarization, Pg, is the
product of the group polarizability, ag, by the effective field, Edp’ and

is equal to the induced dipole moment, mi (Equations 1, 8, 11).

Pg = agEdp =mi

 

 

 

The components of polarizability in the plane of the C—-—C bond
are given in Table XXIX (20).
Table XXIX-—Group Polarizabilities
L L r...

 

M ethyl Ethyl I s opropyl t - Butyl

 

Polarizability (x 10--25 cm3) 27 46 65 84

 

The sum of the unknown principal contribution and the product of
the polarizability by the unknown E dp may be taken as equal to the
experimental electric moment for two compounds of known u. These
equations may then be solved simultaneously and the resulting values
of the principal moment and Edp used to calculate the electric moment

in other cases.

80

This calculation was made solving the equations for propyne and
3-methy1-1-butyne simultaneously and calculating the moment of

3, 3-dimethy1-1-butyne as follows;

_ H1 ' Hz
Edp_ a1 -0.2

_ “Mm-Hz)
x l 0'1" °~z

3, 3-Dimethyl—1-butyne “calc = 0.81 D.

The agreement between this value and the observed value lends
considerable support to the interpretation of variations of the moments

of these molecules in terms of dipole induced-dipole interactions.

1, 4 - Cyclohexanedione

 

Calculation of the energy differences between conformational
isomers by Equation 28 requires that the number of energy levels be
limited to two and hence, that the number of possible conformations of
the molecule under study be limited to two. Examination of the
1, 4-cyclohexanedione molecule reveals that as well as forms IX and X
a pair of enantiomorphic forms, XI, may be imagined for the

molecule .

81

 

The moment of the molecule in the chair conformation, X, may
be estimated to be zero by inspection, and those of the two boat forms
calculated by taking the vector sum of two cyclohexanone moments at

an angle of 76 degrees in IX and 128 degrees in X1. Thus;

mIX : 4.2 Do

mXI : 2.3 Do

If the energies of the various boat and chair forms were equal,
the net or measured moment would be the root mean square of these

(giving m a statistical weight of two). This mean is 2. 66 D. ,

XI
considerably larger than the measured moment, indicating that in the

actual molecule the chair form is favored over one or both of the boats.

82

Inspection of the molecular models of this molecule reveals that
in the chair form, X, the intramolecular interactions, other than those
between hydrogen atoms oriented in the skew configuration, consist of
interaction between four hydrogen atoms in the eclipsed conformation
with respect to the two oxygen atoms (OI-H1 in X). The interactions in
form IX consist of those between eight hydrogen atoms eclipsed in pairs
(HI-H2 in IX), four hydrogen-oxygen interactions of the type found in
form X, and, probably, an interaction between the two oxygen atoms.
In either form XI enantiomorph there are two hydrogen-oxygen inter-
actions of the same type found in the other two forms, interaction between
the two axial hydrogen atoms at the peaks of the boat (HI-Hz in X1), and
perhaps, a small interaction between the two oxygen atoms. The energies
of the three forms would, on the basis of these considerations, be
expected to be in the following order;

< <
EX EIX EXI

It is also possible that a form such as XII has a role in

O: ”=0

XII

the determination of the net moment (41). The CHZCOCHZ bond angle

in this form is calculated to be 111020' on the basis of -a tetrahedral

angle of 109028' for the other bonds.’ This is very close to .the value

of the C-fi-C angle found in a large number of compounds (40), indicating
that the energy of the molecule in this form would not be greatly increased
by bond strain. Furthermore the intramolecular interactions in this

molecule are practically identical to those found in the chair form X.

83

No means is available by which the various possible combinations
may be sorted out, since no relation is known by which the energy of
one form may be expressed in terms of another except the simple two
level relation of Equation 28. ' An estimate may be made, however, of
the difference in energy between the chair form X, and the composite
boat form which has been termed the flexible form- (41). If it is assumed
that only the three unstrained forms need be considered and that the

energies of IX and XI are the same, the approximate value of AE is

k
l, 4-Cyclohexanedione AE = EF-FC = 2.11%};

trans - l, 2- Dihalogenocyclohexane s

_‘—‘
1

In the trans-1, 2-dihalogenocyclohexanes, as in other substituted

 

cyclohexanes, the distinguishable conformations of the chair forms are
denoted by reference to the orientation of the substituents with reSpect
to the threefold symmetry axis in the chair form of cyclohexane.

- An axial orientation (a) is parallel to this axis, while an equatorial
orientation (e) forms angles of 110 and 70 degrees with it. Each of the
molecules studied here has a polar (e-e) and a nonpolar (a-a) con-

formation.

 

a—a e-e

XIII XIV

84

The moment of the polar form, XIV, of these molecules may be
estimated from bond moments, or measured directly as the moment of

the cis isomer of the molecule in question. A value of 3.13 D. has

 

been used here for the moment of this form of all three molecules.

This value is the mean of the moments of the three molecules measured

in solution (19), all of which are the same within experimental error.
In Table XXX values of AE between these forms calculated from

vapor phase measurements are compared with values determined from

solution measurements (19), corrected for the decrease in energy of

the polar form in solution. This correction is given by (48)

-( 6 'UHZ
(2 6 +1)af

 

ER:

in which ER is the loss of energy resulting from the transfer of a dipole

of moment (1 from vacuurn('€ : l) to a medium of dielectric constant e ,

where 'a' is the molecular radius.

Table XXX--Energy Differences Between Conformational Isomers for
Some trans- 1, 2—Dihalogenocyclohexanes.V

 

AB = (Eaa - Eee)kcal mole"l

 

 

 

Corr.
Benzene Benzene
Vapor Solution Solution
trans- 1, 2-dichlorocyclo-
hexane 0.13 0.65 '0.05
trans- l-bromo- l-chloro-
cyclohexane -0. 05 0. 37 '0.18
trans- l, 2-dibromocyclo-
hexane -0. 35 -0. 07 '0'.43

 

Values of AE have also been calculated for these compounds from

measurements in CCl4 (see Table II), which are generally in somewhat

85

better agreement with the vapor values reported here. However, when
the correction cited here is applied this agreement disappears.

That the values of AE reported here, as well as those calculated
from solution measurements are approximately correct may be
demonstrated by consideration of the results of similar measurements
on 1, 2-dichloroethane and 1, 2-dichloropropane.

For 1, 2-dichloropr0pane the three possible stable configurations
are represented by the diagrams below, in which the reader is looking

directly along the 1, 2-carbon-carbon bond.

     

anti gauche-1 gauche— 2

 

XV XVI

The gauche-2 form apparently has a much higher energy than either of
the other two forms, and consequently would be expected to exist in
only negligible amounts at ordinary temperatures, an observation which
is in accord with the results of Raman measurements (42). The energy

difference, AE, between the anti and the gauche-1 forms of this mole-

 

cule, calculated (43) from vapor phase moments (44), and that between

the anti and gauche forms, XVII and XVIII,

anti gauche

XVII i XVIII

 

86

of 1, 2-dichloroethane (45) are;

AB = Eg-Ea kcal mole”l
l, 2-Dichloroethane 1. 21 kcal

l, 2-Dichloropropane l. 0 kcal

The difference of 0. 2 kcal can only be attributed to the interaction
between the halogen on carbon number one and the methyl group, carbon
number three, in 1, 2-dichloropropane.

Consideration of the diagrams, XIX and XX of the conformational

 

isomers of the trans-l, 2-dihalogenocyclohexanes reveals that an

 

analogous situation prevails, except that instead of one such halogen-
methyl interaction there are four, two of which occur without the sacrifice
of a halogeni-hydrogen’: interaction. The difference between the energies

of the e-e and a-a conformations of trans-1, 2-dichlorocyclohexane would

 

be predicted on this basis to be somewhat over 0. 8 kcal less than that’
of the anti and gauche forms of 1, 2-dichloroethane, which proves to be

the case, the difference between vapor phase values being about 1. kcal.

SUMMARY

The electric moments of two series of compounds were measured
in the vapor phase by the heterodyne-beat method at radio frequency.

One of the series consisted of six hydrocarbons; two alkanes,
2-methylpropane and 2-methylbutane; two alkenes, iii-Z-butene and

trans-Z-butene; and two alkynes, 3-methy1-l-butyne and 3, 3-dimethyl-l-

 

butyne. Small moments, confirming published microwave results, were

found in the alkanes. The moment of trans-Z-butene was found to be

 

zero, as anticipated in view of its symmetry, while c_i_s--2-butene was
found to have a moment which could be explained, qualitatively, on the
basis of hyperconjugation. The moments of the alkynes were discussed
in terms of both hyperconjugation and dipole induced dipoles.

The second series of compounds consisted of four substituted

cyclohexanes; trans- 1, 2-dichlorocyclohexane, trans- l-bromo-Z-chloro-

cyclohexane, trans-l, 2-dibromocyclohexane, and 1, 4—cyclohexanedione.

 

The moments of these substances were measured over a short range of
high temperatures, and the differences in energy between conformational
isomers calculated in each case. These results were compared to the
results obtained from measurements made on these compounds in solu-

tions of various solvents.

87

N

10.

11.

12.

13.

14.

15.

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