AN INVESTIGATION OF THE ELECTRIC MOMENTS OF VARIOUS ORGANIC AND INORGANIC COMPOUNDS OF FLIJORINE mm Io: the Degree of M. S. MICHIGAN STATE UNIVERSITY Bruce L. Kennedy 1961 E THESIS {3“ I NJCHIGAN STATE UI'JI‘.’ERSITY UI Ailll’i-JuIIJi In.) API-LIED “ _ .' .- L"J|-,: IVE EAST LANSING, MICHIGAN ABSTRACT MOMENTS OF SUBSTANCES IN THE VAPOR PHASE by Bruce L. Kennedy THE ELECTRIC DIPOLE The electric dipole moments of various organic and in— anic compounds have been measured in the gas phase. The propionitrile 1.33D, pentafluoro- propene 2.33D, vinyl nethallene e 44D, org compounds are : pentafluoro propionyl chloride .99D, trifluoromethyl methyl ether 1.05D, ethyl acetylene .76D, perfluoropropylene l.lD, and sulfur tetrafluoride .88D. The method employed in this investigation was the heter— method takes advantage of the depend- odyne-beat method. This itance ence of frequency in an oscillating circuit on the capac of the circuit. Therefore if a dielectric cell is included in this oscillating circuit, e in ubstance in the the capacitance will chang dielectric cell, thereby giving different frequencies for different substances in the cell. If one employs the method with the cell evacuated and then again with a substance in the cell, the frequency diff- e can be determined, and hence the tance can be calculated. The lated to the molar polar- uation. Then by determining efractive index data, the relation to the s erence or capacitance Chang dielectric constant of the subs dielectric constant can then be re ization by the Clausius—Mosotti eq the distortion polarization from r dipole moment of the substance can be determined. The results of this investigation seen to indicate that with a substituted CF3 group exhibit very This is attributed to hyperconjugation CF2 group also exhibit s as is indicated ethylenic compounds large dipole moments. of the CF group. CompoundS with a CF} 3 Very strong electron withdrawing propertie which are occurring in the by considering the various effects O molecules, cracrzém and cr3crecu. The dipole moments of methallene and ethyl acetylene also indicate that hyperconjugation is occurring in these molecules although not to the extent that it is occurring in the CF3 and CFBCFQ groups. The dipole moment of vinyl methyl ether is consistent with those of other ethers, but is slightly less, presumably because of resonance of the type, + .- CH3-oscu-cuz The moment of sulfur tetrafluoride indicates that the sp3d hybridization with an unshared pair occuping a hybrid orbital is very probable. AN INVESTIGATION OF THE ELECTRIC MOMENTS OF VARIOUS ORGANIC AND INORGANIC COMPOUNDS OF FLUORINE By Bruce L. Kennedy A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemistry 1961 ACKNOWLEDGMENT The writer wishes to express his appreciation to Professor M.T.Rogers for his assistance throughout the course of this work. 11 TABLE OF CONTENTS I. THEORETICAL BACKGROUND Derrivation of De Derrivation of Cl Relation Between Equations bye Equation ausius-Mosotti Equation Debye and Clausius-Mosotti II. EXPERIMENTAL Principle of Heterod Variable Oscillator Fixed Oscillator Precision Condenser Temperature Measurement Temperature Control Gas Handling System Dielectric Cell Experimental Method III. DATA AND RESULTS Materials Ethyl Acetylene Vinyl Methyl Ether PentafluoroprOpionitrile 2—Trifluoromethylpropene PentafluorOpropionyl Chloride Methallene PerfluoroprOpylene Sulfur Tetrafluoride Discussion of Error yne-Beat Method IV. DISCUSSION Interpretation 0 Resonance Induced Dipoles Atomic Dipoles Dipoles Due to Difference in Electroneg- ativity of Carbon Atoms Bond Moments Used in This Investigation Interpretation of Momen Investigation 2-Trifluoromethylpropene PerfluorOpropylene Pentafluoropropionitrile PentafluorOpropionyl Chloride f Moments ts Obtained in This iii. Page 12 6b 6b 60 b7 68 TABLE OF CONTENTS - Continued V. Bibliography Methallene Ethyl Acetylene Vinyl Methyl Ether Sulfur Tetrafluoride iv. Page 68 69 7O 7O 72 Table II III IV VI VII VIII IX XI XII XIII XIV XV XVI XVII XVIII XIX XX XXI XXII LIST OF TABLES Data for the Calibration of the Precision Condenser Data for the COpper-Const Dielectric Constant Data for Ammonia Vapor as a Function of Temperature Calibration with Ammonia for Ethyl Acetylene (lst determination) Ethyl Acetylene (1st determination) Calibration with Ammonia for Ethyl Acetylene (2nd determination) Ethyl Acetylene (2nd determination) Calibration with Ammonia for Vinyl Methyl Ether (lst determination) Methyl Ether (lst determination) yl Methyl Ether antan Thermocouple Vinyl Calibration with Ammonia for Vin (2nd determination) Vinyl Methyl Ether (2nd determination) Calibration with Ammonia for PentafluoroprOpio- nitrile (lst determination) Pentafluoropropionitrile (1 Calibration with Ammonia for PentafluorOpropio- nitrile (2nd determination) PentafluorOpropionitrile (2nd determination) Calibration with Ammonia for PentafluorOpropio- nitrile (3rd determination) ionitrile (3rd determination) Trifluoromethyl- st determination) Pentafluoroprop Calibration with Ammonia for 2— prOpene (lst determination) 2—Trifluoromethylpr0pene (lst determination) Calibration with Ammonia for 2-Trifluoromethy1- prOpene (2nd determination) 2-Trifluoromethylpropene (2nd d for 2-Trif1uoromethyl- etermination) Calibration with Ammonia prOpene (3rd determination) V. Page 14 15 22 25 26 27 28 29 3O 31 32 33 34 35 36 37 38 39 4O 41 42 42 LIST OF TABLES — Continued Table XXIII XXIV XXV XXVI XXVII XXVIII XXIX XXX XXXI XXXII XXXIII XXXIV XXXV XXXVI XXXVII XXXVIII 2-Trif1uoromethylpr0pene (3rd determination) Calibration with Ammonia for PentafluorOprOpionyl Chloride (lst determination) PentafluorOprOpionyl Chloride (lst determination) Calibration with Ammonia for PentafluorOpropionyl Chloride (2nd determination) Pentafluoropropionyl Chloride (2nd determination) Calibration with Ammonia for Methallene (lst deter- mination) Methallene (lst determination) ' Calibration with Ammonia for Methallene (2nd deter- mination) Methallene (2nd determination) Calibration with Ammonia for PerfluorOprOpylene PerfluoroprOpylene Calibration with Ammonia for Sulfur Tetrafluoride (lst determination) Sulfur Tetrafluoride (lst determination) Calibration with Ammonia for Sulfur Tetrafluoride (2nd determination) Sulfur Tetrafluoride (2nd determination) Moments vi. Page 44 45 4o 47 48 49 5O 51 52 53 54 55 56 57 58 59 LIST OF FIGURES Figure I Gas Handling System II Dielectric Cell vii. Page 18 I. Theoretical Background When a dielectric material is subjected to an electric field, the molecules in the dielectric are said to be polar- ized by the field. Polarization occurs by distortion and by orientation. Distortion polarization is due to the fact that positive and negative charge centers in the molecules are induced so as to line up .L made to separate, and hence a dipole is with the field. Orientation polarization occurs when the molecule has a permanent dipole. When acted upon by the field, the permanent dipole tends to line up in the direction of the field. The first effect is independent of temperature since a dipole disturbed by thermal collisions from its equilibrium position is at once induced again by the field. The orienta~ tion polarization is dependent on temperature, decreasing with an increase in temperature. This is due to an increase in the number of thermal collisions at higher temperatures, and hence the force of alignment imposed by the field is being overcome. The objective of this section is to derive a relation- ship from which the total polarization can be obtained (1), and then to snow the relationship between polarization and the dipole moment. polar dielectric material under the influence Consider a of an electric field. Let the small vibrations of the charges about their equilibrium configurations be specified by a set of normal coordinrtesfj;' ...... equal in number to the number of degrees of freedom of the elastic vibrations. One assumes the electrical moments px,. py, afld P2. along the principal axes of inertia x', y' and z' to be linear functions of the normal coordinates; therefore, pxl = uxvs‘ Z cX'ifi (I) 1. 2. where ux, is the component of the permanent moment along the principal axis of inertia, x', and the terms inside the summ- ation are those representing polarizations acquired by virtue of the elastic vibrations. Let e,¢ and ‘I’ be the angles specifying the position of y' and 2' which are fixed in the principal axes of inertia x', the molecule relative to another set of axes x, y, and 2 which are fixed in space.Qis the angle between z and z', and 49 and Vlare the angles between the intersection of the xy ani x'y' planes and the x and x' axes respectively. The kinetic energy of rotation of the molecule regarded as a rigid body is then 1 " 3- 1‘ T :3 *5— ( Ax,flx, Ay,ny. Az'nz' ) (2) 12“,: écosIu O sinfi‘sin'}I 11/: écos‘f’sine - é sin‘Y J14”: ‘V + ¢cose where the A's are the principal moments of inertia and the il's are the components of angular velocity. Then the (3) Hamiltonion function is given by 2 1 2 1 2 1 2 l 2 l a. . x y 2 V’ - ' -E[(ux, +ch,ifi)smésinI/’+ (uy, +ch,ifi)smecos4' + (uz, +Xcz,ifi)cose where P = o :- cos‘ljpee- SIHV’ COSeCQ (p¢ 00591)?) Q = _ sian 4» cosV’cosece(p - 00591)) e O T’ R - p W The first term is the kinetic energy of the molecule regarded as a rigid body, and the second and third terms are 3. the kinetic and potential energy respectively of the small vibrations. The fourth term is the potential energy due to the applied electric field. The expression for the polarization involves the average moment of a large number of molecules. Such an average can be calculated if the probability that a molecule have any con- figuration is known. This probability is given by the Boltzmann distribution function. Then, by integrating over all possible configurations, the partition function for the system is, Z=Mo--Ie“H/fld d ddddd d p): pf} 19ng p4, 7r, in" edddv (4) In order to perform the integration it is convenient to change three of the variables p6”p¢,pw to P, Q and B. This trans- formation can be represented by sine dP dQ dR d%d%d%’= (W Then the Hamiltonian takes the form, H: macs p5......) +g(9q§¢f’....E) (6) and the partition function can be factored into, 2 : 212 (7) n C where (8) z1 =[/...j/ e’f/kT deQdR dfirdf; Z,2 =f/.../ e"g/kT sinQdedcbd‘I’df-‘dfl..... J The electric susceptibility can then be obtained from, (9) J In Z - NkT ‘ ( 1n Z1 + In Z2 ) IkT E X=—__ E Eh) 35h but since 21“ Zl(E), the Z1 makes no contribution to the susceptibility and hence, FR“ F3 35:” This means that the polarization is the same as though the 3’1n Z as 2 . (10) 1 kinetic energy were omitted entirely from the Hamiltonion function, provided the weight function sineais retained. Hence, for Z 2 2 i l Zia. .E . . Z2 :¢[...jpe- 2kT 1? e- kT<.= N ‘I 3kT L:l 331 If the oscillations are due to isotropically bound charges, 2 “2 2_2 Cx'i = Vy'i 2 szi - 81 (17) Therefore, M 5 X=N,_Z.e_i_ 4- m2 (’8) a1 3kT where the first term is the molecular polarizabilitgqo. Hence the polarization in a field of unit field strength is given by P _ igllL («o + “2/3kT) (19) where the first term is the distortion polarization and the second'term is the orientation polarization. It is desirable to know the effective average field or the force to which a molecule is subjected when a field is applied (2). This force may be resolved into three parts: —- ‘9—9 Flocal ='¥3 + F2 + F3 (20) '?i is the force due to the applied electric field and is given by ‘51 :: 47757? (21) whereozis the surface charge density on the conducting plates between which a dielectric material has been placed. $2 takes into account the attractions and repulsions by other molecules ..., polarized under the influence of the external field. F2 is given by, = - 4le3 <0- E (22) 3 —_5 ...9 where P is the polarization vector. F3 takes into consideration ... F2 the internal field exerted by other charges within the same molecule. In general, T; is very small and is taken as zero. However, it is a very complicated function and is temperature —9 dependent. Neglecting F , the local field is, ‘4' - —*' 46% 5E’ (2 Flocal - “for- * 3 3) Using the relationships, —* - D : 4770"" (1‘4) and E = ”D. - 4"? (if) Q a where E is the electric intensity vector and D is the electric 7. displacement vector, equation(23) becomes, «b '4 ...-5 Flocal = E + 5%2 (26) where the first term represents the average field throughout the dielectric, and the second term represents a correction for the fact that the other molecules of the dielectric exert an average force on the given molecule when the dielectric is subject to E. The average moment of one molecule is ... 4 I = O‘Flocal (23) wherecx is the sum of the induced and permanent polarizability. The molar polarization is given by, Q P - n? (28) 3 where n is the number of molecules/cm . By substituting equations 25 and 26 into 27, -- ..a A = MPiocei ‘3 “a“ B + 93-13 ) (29) ’9 Using the relation, D -€;E, and equation 25, equation 29 becomes, €_ 1 : 4nn a (30) 6+ 2 3 wheres is the dielectric constant of the substance. Multiplying equation (30) through by the ratio of the molecular weight of the dielectric to its density gives, 91 e- 1) = tumor (31) d (€'+ 2 3 where N is Avogadro's number. Sincecxwas the sum of the induced and permanent polerizabilities, equation (31) is identical with equation (19). Hence, P = ée— l; 34 (32) 6+ 2 d 8. Hence, the molar polarization can be obtained experiment- ally by measurements of dielectric constants and can then be related to the distortion and orientation polarization. However, in order to calculate dipole moments, the distortion polarization must be obtained. This is done by taking into consideration the fact that the dielectric constant is equal to the square of the refractive index at infinite wavelength. That is. Q: 1'12 (34) and therefore, 2 --—=—- -:§- 05> n + 2 where Pd is the distortion polarization. It is Significant to elaborate on this point. In order to measure the refractive index, visible light is used. The electromagnetic forces associated with visible light oscillate very rapidly in sign and hence don't act in any one direction long enough to orient molecules in any one direction. Hence the refractive index measured with visible light is due entirely to distortion polarization. Therefore, extrapolation of such data to infin- ite wave—length will yield only the part of the dielectric constant exclusive of orientation. Furthermore, the distortion polarization is the sum of two terms: atomic and electronic. The atomic polarization is due to vibrations of nuclei, but since nuclei generally have vibrational frequencies in the infra-red, the atomic polarization contributes very little to the distortion polarization when measured with visible light. Therefore, the distortion polarization is due almost entirely to electronic polarization when refractive indices are measured in this manner. Hence the dipole moment can be readily calculated in terms of, P.P+P:P+mu2=€-1 M (36) d o d —--——--a- or, by solving for u , gig—Led” -Pfl-‘ (37) u $7“ [(41+27d dj Experimental The method employed was the heterodyne-beat nethod, and all samples were measured in the gaseous phase. This method takes advantage of the dependence of the frequency of an (3) electron tube oscillator upon resistance, inductance and cap- acitance in its tank circuit. .A circuit with C, L and R will be set into oscillation if the capacitor is suddenly given a charge and then left to discharge. From this oscillating circuit, electromagnetic radiation is generated. If two such oscillators are loosely coupled, one a fixed oscillator gen- erating a radiofrequency f0 , and the other a variable oscillator generating a radiofrequency f , and if these sig- nals are fed into a mixer tube whose function it is to produce in its output voltage a component of frequency f - f0, this difference frequency or beat frequency will be in the audio range when f and fo are nearly equal. This can be detected by earphones or other suitable means. The frequency of the vari- able oscillator will be given very nearly by, r: 1 21855 where L and C are the inductance and capacity of the oscillat- (38) ing tuning circuit. If for some capacitance setting, f is greater than f“, the beat frequency will be outside the audible range. An increase in C ( L is fixed ) will lower the beat frequency which will pass through the audible range and will reach zero when f = f. . A further increase in C will again produce a beat note which will now increase with C until it passes beyond audibility . The region of inaudibility is so narrow as to correspond to a point on a precision measuring condenser in the variable oscillator. This corresponds to 10. 11. y to within one cps, and hence Location of the beat frequenc the accuracy of is determined by the accuracy of this method condenser and by the setting and calibrating the standard variable and fixed oscillators. nnecting a dielectric cell in par illator circuit, a change in capacitance can be altering the medium within the cell. Then, a for inaudflnlity before ance into the dielectric cell stability of the Hence, by co allel to the variable osc effected by measurement of the beat frequency after introduction of a subst e substance. to measure dielectric and will give the capacitance of tn it is much harder e their dielectric constants are so changes to be very s employed.This In general, constants of gases sinc closefv unity) thereby causing capacitance small. Hence, a third source of oscillations i c has a fixed frequency. The beat frequency for so that it is equal to This elimin- source als inaudibility is then adjusted this third source rather than to zero frequency. ates the so-called locking-in effect of the fixed and variable ibed. That is, when f is brought oscillatorSinitially descr be distinguished low frequency beats cannot ble of the two oscillators exerts a synchronizing action on the less stable and over a consider- he two oscillators are locked in step with one obtained. The third close to fo , because the more sta able range t and a sharp zero beat cannot be tigation generated a t frequency was 400 another source of oscillations in this inves Then, when the bea frequency of 400 cps. o-one Lissajous figure on an oscilli— cps, one observed a one—t sc0pe. _Xariable Oscillatg;_ ble frequency oscillator made use of a 6A8-type The Varia rter tube (4) which exhibits a negative trans- pentagrid conve 12. conductance between the signal grid and the anode grid. Under these conditions, the screen current remained fairly constant for wide variations in signal-grid voltage, and the frequency at which the tube oscillated was relatively independent of stray signal feedback through the plate. This design resulted in an oscillator of high frequency stability, and one which should not be affected by the frequency of the fixed oscilla- tore Fix A crystal replaced the tuning circuit found in most oscillators (4) , and hence the oscillator required no tuning adjustment and would work without change of components over a wide range of crystal frequencies. A 6SJ7 pentode tube was used as a triode oscillator, with the cathode and suppressor grid grounded. This provided screening against capacitance coupling of the oscillator to later stages, so that the frequency or oscillation was less affected by feedback through the plate. Each oscillator was shielded by enclosure in a separate metal box, and the signal output of each was fed to the mixer tube through coaxial leads. The entire apparatus was enclosed in a thermally insulated aluminum box. 13. Precision Condensg; A General Radio Type 792-N precision condenser with a range of 1100 scale divisions was used to measure capacitance. Since this instrument was in scale divisions, it had to be calibrated in terms of capacitance. This was accomplished by determining the change in capacitance on the precision condenser relative to a primary standard capacitor. The primary standard capacitor (5) was designed so that the cap— acitance change per inch of travel on it was equal to 1.4800 uuf or .0001057 uuf per scale division. The error in deter- mining capacitance by this method was about l%, but since all measurements of capacitance involved capacitance incre- ments, the error was minimized. Table I gives the data for the calibration. Temperature Measurement The temperature inside the dielectric cell was determined with a c0pper-constantan (60% Cu—40% Ni) thermocouple. The cold junction consisted of a crushed ice-distilled water mixture. All switches and connections were made of COpper so that the only junctions of different metals were those of the thermocouples. The resulting electromotive force was measured with a EE2 type potentiometer (Leeds and Northrup). A plot of emf vs. temperature was made for the COpper— con - stantan thermocouple, the data being taken from the National Bureau of Standards (6). Hence the temperature for any emf could be determined. The sensitivity was such that a change in temperature of‘ 0.1 degree could easily be detected.' Table II gives emf vs. temperature data. 14. Table I Calibration of Precision Condenser Scale Divisions Scale Divisions (precision condenser) (standard condenser) 0.0 100 43.5 125 87.2 150 131.4 175 173.2 200 217.6 225 262.8 250 307.0 275 354.1 300 “396.1 323 429.2 350 481.8 375 524.0 400 565.3 425 604.9 450 643.7 475 683.4 500 722.1 525 760.0 550 797.6 575 834.7 600 872.3 625 909.1 650 944.8 67b 981.8 700 1016.7 723 1051.8 730 1086.3 773 1155.6 823 1188.9 850 1221.6 875 1255.3 900 1288.1 925 1321.7 950 1354.5 975 1000 1385.4 it . . . data are for p051tion l on.pre01sion condenser 15. Table II _Temperature Measurement - Copper—Constantan Thernocouple Temperature 0C EMF (millivolts) 0.0 .0.0 10.0 0.39 20.0 0.79 50.0 1.19 40.0 1.61 50.0 2.03 63.0 2.47 70.0 2.91 80.0 3.36 90.0 3.81 4.28 100.0 16. Temperature Control The dielectric cell was immersed in an asbestos bath. The temperature within the cell was controlled by a thermistor in a.Wheatstone bridge circuit. The thermistor was of the glass- coated rod type with Pt-Ni alloy leads? Its resistance varies from 145000 ohms at 0°C to 505 ohms at 200°C. The other resistors in the bridge set-up were a 4-decade resistance box with a range of l to 10,000 ohms and a ten-turn helical potentiometer. The heater current was controlled by a sat— urable reactor in series with a heater. The circuit was supposed to control the temperature within.:.05 degrees. However, temperature variations of as much as a degree were observed. A change in temperature of a degree during a measurement did not effect the value of the dipole moment to any appreciable extent provided no marked change in the replaceable capacitance of the cell accompanied this change. When the replaceable capacitance did change appreciably, the data obtainedvmre no longer consistent,and hence one could tell if temperature changes were effecting the measurements. Inconsistent data due to temperature changes were discarded. For a more extensive description of the temperature control apparatus, see reference (7). Gas H dling System Before any gas was let into the system, the system was thoroughly evacuated with a Duo Seal Vacuum Pump**. Then, since the cell had to be calibrated before each use, the L * Western Electric Company, Type l4-B ** w. n. welsh Manufacturing Company -) ’1 l7. calibrating gas, ammonia, was let into the system at B and solidified in tube C with liquid air (see diagram,page 18). The ammonia was then condensed and re-solidified into tube D. The system was again evacuated so as to remove any traces of air that may have been present in the system or in the ammonia. This process was continued until any air present had been the vapors flowing removed. Then the ammonia was vaporized into the dielectric cell. The pressure of the gas within the system could then be determined by the mercury manometer. After having calibrated the cell, the ammonia was pumped out, the vapor being solidified in a removable liquid air trap, E. After pumping on the system for a short period of time , the gas whose dielectric constant was to be measured was allowed to enter at A. The same process of condensation and solidification was again carried out until all traces of air had been removed. The gas was then allowed to enter the dielectric cell so as to make a measurement. The entire gas handling system was constructed with high vacuum glass stopcocks. The st0pcock grease used was Dow Corning high vacuum grease. W (The dielectric cell consisted of a series Of'nickel- plated capper cylinders insulated from each other by small Teflon spacers. The plates were sealed in glass so as not to allow any air to enter the cell. Platinum leads connected the cylinders to tungsten wires which were sealed through the glass casing. The tungsten wires were connected to the heterodyne- beat apparatus by a coaxial lead. Since the capacitance is directly proportional to the area of the plates and inversely pr0portional to the distance 18. Figure I Gas Handling System To (.... f_i an? Manometer ; I g ‘3 a i s ‘f Ewe/1‘ To Unknown Gas ' t?L Cylinder “ :fi ’ Cell ; LJ @ r \ 1 t .I L... > T0 *hnl ”*7 v 3 Vacuum ‘9 ' U LiqLfiid Pump I TO Air ‘filNHE Trap :}Cy inder 9 Glass vacuum stopcocks 19. between them, the largest ratio of A/d would give the largest value for Co' the replaceable capacitance . A large Co is a necessity when working with gases since the capacitance increments are so small. However, the larger the ratio of A/d the greater the absorption error. Therefore, the cell described above (4) was constructed with these two factors in mind. As the replaceable capacitance , which is.a function a result, of temperature, pressure,and humidity changed periodically, and since it was large relative to capacitance changes, a change in Co had a marked effect on the measured quantities. Therefore, Co had to be determined each time a series of The method of cell calibration measurements was to be made. will be described more fully in a following section.See page 20 for a diagram of tne dielectric cell. Experimental Method Since the replaceable capacitance, Co’ changed period- ically, the cell had to be calibrated each time a determination was to be made. This was done in the following manner: The total capacitance of'the evacuated cell is given by Cv : Co + Cf (39) where CI. is the capacitance associated witn leads and parts of the cell which can not be filled with gas. The total capacitance with a dielectric material in the cell is given by Cg 3600 + Cf (40) where E is the dielectric constant of tne material in the cell. By solving these two equations simultaneously, Cf can be eliminated and the result is Cg ‘ CV (30 (+1) c.=_____€_l -.- E_1 rQ-—- -... ...—i ...l- 20. Figure 11 Dielectric Cell t l f i i g l J 3; , : Inches i t J g E 2.3 5 i: C Jim 1: a/% D ‘35711L/5 E "f 9 4% 7987? a 1" .._L _I‘J) Thermocouple Well Connection to vacuum line Leads to heterodyne-beat apparatus Nickel-plated copper cylinders Teflon insulators 21. whereiXC represents the difference in capacitance between the empty cell and the cell filled with a dielectric material. .AC is given by(dC/dE)760; it is the capacitance change at a pressure of one atmosphere. Hence by knowing the variation of dielectric constant with temperature for some gas at a given pressure, ammonia in this investigation,'the replaceable cap- acitance can be determined. Then the dielectric constant of a gas under investigation is given by, €. =-. 977g . 1 Adela? 760 + 1 (42) U 0 O The method used to determine the 510pe,dC/dP, was as follows: The capacitance at a low pressure,about 200mm,and the capacitance at a higher pressure, about 300mm., was determined. This process was repeated as many times as was necessary to get good reproducibility in the quantity dC/dP. Then, hrving determined the dielectric constant, it was related to the molar polarization by sea—<2) where M/d was the molar volume of the gas. By assuming that the gases were ideal, Vll = RT/l. Then by using refractive inde>< data to determine the distortion polarization, Pd, the dipole moment was determined from, (44) and U:EQ(PI-Pd) (45) 22. Table III Dielectric Constants of Ammonia Vapor at Several Temperatures Temperature (0C) (6 - 1)x106 29.95 5826 38.72 5522 47.59 5240 58.56 4916 71.44 4581 80.33 4369 92.21 4062 116.12 3498 :EData from Van Itterbeck and de Clippeleir, Physica,‘lfi,349 (1948). DATA AND RESULTS 23. 1. 2. 3. 4. 5. 9. 24. Materials Sulfur Tetrafluoride - purity 90-94% - impurities, SOF2 5-9%. C12 .3% , - E. I. Du Pont de Nemours and CO., Inc., Wilmington, Delaware. PerfluorOpropylene - literature B. P. -33° C, observed B. P. -300 C - Peninsular ChemResearch, Inc., Gainesville, Florida. PentafluorOprOpionyl Chloride - literature B. P. 9.50 C, observed B.P. 7-90 C - Peninsular ChemResearch, Inc., Gaines- ville, Florida. PentafluorOpropionitrile - literature B.P. ? , observed B.P. -30° C - Peninsular ChemResearch, Inc.,Gainesville, Florida. TrifluoronethylprOpene - literature B.P. 6. 4° C, observed B. P. 6-7o C - Peninsular ChenResearch, Inc., Gainesville Florida. Ammonia,anhydrous - purity 99. 99% min. - Matheson Co., Inc., Joliet, Illinois. Ethyl Acetylene - purity 95.0% min. - Matheson CO., Inc., Joliet, Illinois. Vinyl methyl ether - purity 95.0% min. — Matheson CO., Inc., Joliet, Illinois. Methallene - purity 98.0% min. - Columbia Organic Chemical CO. 25. Table IV Calibration with Ammonia for Ethyl Acetylene (lst determination) Pressure AP Precision Standard AC AC/AP cm. of Hg Cm. of Hg Condenser Condenser ,unf ,quf/cn 0. 2 .2 2.0 3 53 17.55 99 35 0.2495 0.01422 12.98 438.6 588.0 30.96 17 45 287.7 332.0 2421 01388 13.51 ' 422.2 561.0 ' - ‘ 30.96 280.1 319.0 1 .2 .2505 .01374 12.73 8 3 419.3 556.0 3 . 2 1.0 30.86 17.84 265 0 9 .2537 .01422 13.02 404.0 531.0 6 'AC/AP (E - l)x10 Co average at 48.3OC 0.01402 5218 204. z Table V Ethyl Acetylene (lst determination) Pressure AP Precision Standard 4C AC/AP cm. of Hg cm. of Ag Condenser Condenser'.qmu‘ ugf/cm 32.52 305.2 363.0 0 1723 0 008918 13.20 19'32 400.4 526.0 ' ° 32.01 18 92 247.1 258.0 1723 009106 13.09 ' 339.1 421.0 ' ' 32.64 19.89 225.9 220.0 .1807 .909080 12.75 320.6 391.0 AC/A‘P E Pd Pl! P. 11 average at 48°C CD13 cm} cm3 Debye (3.009035 1.003363 18.88 29.57 10.69 0.75 27. Table VI Calibration with Ammonia for Ethyl Acetylene ( 2nd determination ) —‘ Pressure AP Precision Standard AC AC/AP on. of Hg cm. of Hg Condenser Condenser ,uuf RRf/C‘ 29.38 260.7 284.0 0.2716 0.01405 10.06 19°32 410.3 541.0 30.45 246.6 257.0 16.7 .2357 .01408 13.70 5 373.7 480.0 34.32 22.20 219-7 209'0 .3150 ,01419 12.12 389.4 507.0 .0 . 30°86 16,96 “9‘4 262 .2368 .01396 13.90 377.4 486.0 6 sc/Ap (e- 1)x10 Co average at 49.8 0C M41!“ (3.01407 5175 206-63 28. Tabl e VI I Ethyl Acetylene ( 2nd determination) Pressure .LP Precision Standard ‘00 AC/AP cm. of Hg cm. of ng Condenser Condenser uuf .quf/cm, M . 20.7 390.0 31 ab 18.30 3 0.1723 0. 009415 13.56 417.2 553.0 32°81 320 3 388.0 18.94 ' .1744 .009208 13°87 416.8 553.0 —_7 - .0 31'90 18.41 323'1 393 .1712 .009291 13.49 418.5 555.0 32‘29 18,38 305°4 363'0 .1712 .009315 13.91 400.4 525.0 AC aP (i P Pd P u avérage at 49.6 0C 05113 01113 c133 Deybe —‘ 0.009307 1.003423 30.23 18.88 11.34 0.77 ; 29. Table VIII Calibration with Ammonia for Vinyl Methyl Ether (lst determination) . --- .. ...... ..- ..--__..—..-_- ‘-_-_ -. -..—...- ... _ —.-’r - Pressure AP Precision Standard AC AC/AP cm. of Hg cm. of Hg Condenser Condenser .uuf .uuf/cm. _.,1_“_-m__ _ -,“._-. _u_-u_-- -w;-”._. - 4515.40-“ 97-39 13.33 336 4 4 ,5 0.1924 0.01444 14.06 444.9. 59/.0 30.77 17 313-2 376") 2516 .01452 13.44 '33 455.8 614.0 25.41 12 11 300.2 357.0 .1744 .31440 13.30 ° 398.2 522.0 6 C AC/AP (€- l)xl0 0. average at 46.5 0C 404# 0.01445 5275 208.23 ; 30. Table IX Vinyl Methyl Ether (lst determination) Pressure AP Precision Standard 4C AC/AP en. of Hg cm.0f Hg Condenser Condenser Juuf ART/cm. . .6 8.0 32 14 19.40 312 47 0.2389 (1.01231 12.74' 514.3 704.0 32.56 372.3 477.0 1 .00 .2 7 .01239 13.56 9 511.0 700.0 35 32.62 377.0 486.0 1 . 1 .227 301177 13.31 9 3 512.0 701.0 3 32'87 18 92 369°8 474'0 .2251 .31190 13.95 ' 502.9 687.0 32.85 19.43 373.0 479.0 .2484 .01278 13.42 519.9 714.0 AC/AP é: Pm Pd P0 ‘ u average at 46-0 OC cm3 cm3 cm3 Debye 0.01223 1.004464 38.97 17.28 2L69 1.06 M 31. Table X Calibration with Ammonia for Vinyl Methyl Ether (2nd determination ) _, - W .. 4 ’7’ "' L"-4W'WM‘OW«BBLxfifi:t mwuw-I’immu ww— —.—... $7 -.. —— 7-..?“ ' 4““va1‘.‘ Pressure AP Precision Standard AC AC/AP cm. of Hg cm.of Hg Condenser Condenser .uuf .uyf/cn, _ ‘ 31.42 334°4 412°C <1 2473 0 01445 14.31 17'11 476.4 646.0 ‘ ‘ 32.14 1 330°8 407'0 2473 01412 14.63 17°5 472.7 641.0 ° ' .6 70.0 32'21 18.58 509 _ 3 - .2695 .01450 13.63 462.6 025.0 6 AC/AP (e- 1 )x10 00 average at 45.900 ...a; _‘_A ~ .. --- .1‘ ‘ 0.01436 5292 206.23 32. Table XI Vinyl Methyl Ether (2nd determination) Pressure ‘25» Precision Standard. AC AC/AP cm. of Hg cm. of Hg Condenser Condenser .qpf .quf/cm. e ' 0 48000 ‘ 32 42 19.79 374 2 , 0.2294 0.01159 12.63 508.7 691.0 . 8 .8 498.0 32 14 18.75 3 3 .2199 001172 13.39 515.0 706.0 _7 ' .8 487.0 3?°46 18.63 3,7 .2347 .01251 13.83 517.4 709.0 ’ .0 . 32.66 20 1]. 384-9 999 .2452 £1219 2.55 ° 530.6 {31.0 .77757wmv T '. A ””7‘ 02.0 33.15 19.40 389 4 5 .2368 .01221 13.75 528.4 726.0 AC/AP 6 1"m Pd lJ0 11 average at 45.703 CH13 0m} cm3 Deybe 0.61204 1.004389 38.3 17.28 21°04 1'05 _-._—-,... .-. 33. Table XII Calibration with Ammonia for PentafluoroprOpionitrile ( lst determination) Pressure AP Precision Standard AC AC/AP cm. of Hg Cm. of Hg Condenser Condenser ,quf .uuf/cn. 34.30 496.9 678.0 7 82 .01 28 12.17 2‘°13 711.2 998.0 (333 0 5 38.31 25 29 450-5 613°C .3808 .01506 13.02 ‘ 694.2 973.0 ‘7 6 . 628.0 38'17 25.69 4 4 5 , .3932 .01531 12.48 713.0 1000.0 39.81 26 37 450.3 005°C .4069 .01543 13.44 ' 706.1 990.0 6 c AC/AP (a — 1)x10 0 average at 44.600 44/ C).Ol527 5335 217.5 34. Table XIII PentafluoroprOpionitrile ( lst determination ) “-..-0‘s“- . -—' ——— Pressure AP Precision Standard AC AC/AP cm. of Hg cm. of Hg Condenser Condenser unf’ Hui/cm. ‘ - — ...—”O - 39.94 487.6 664.0 0.4704 0.01598 10.52 29'42 790.6 1109.0 9 v “r ‘3‘" 7 e 68 e O 37.53 26.46 504 1 9 .4186 .01582 11.07 773.4 1085.0 38°18 26.85 497°6 980’0 .4228 .01575 11.33 769.8 1080.0 AC/AP g Pm rd 10 u 0.31585 1.005539 48.19 14.69 33.50 1.32 v ‘ Calibration w 35. Table XIV with.Anlonia for PentafluoroprOpionitrile (2nd determination) r Pressure AP Precision Standard AC AC/AP cm. of Hg can. of 11g. Condenser Condenser surf turf/cu. 33.93 437.6 586.0 0.3160 0.01478 . 8 11.55 21 3 634.3 885.0 . 0 . 4.0 36 86 23.9? 4 5 7 53 .3425 .01432 12.94 616.2 858.0 . 78.0 , 35.02 2?.45 439 7 5 3 3277 .01460 12.57 635.5 889-0 34-91 21 94 440’9 592'0 .3224 .01470 12.97 ° 641.7 897.0 -.--- -..- .. .... -.. ..-.......--..—... ¢-.-.b.-—Mwflmm*fi J10 35.31 on 44 446.9 60 .3224 .01437 12.87 “' 647°3 905'0 6 c AC/AP (5- 1)x10 0 average at 48.200 “(if 0 .01455 36. Table XV PentafluorOpropionitrile ( 2nd determination) *7 Pressure AP Precision Standard AC AC/AP cm. of Hg cm.of Hg Condenser Condenser .qnf Aggy/cm. . 426.2 568.0 36 41 24.68 0.3953 0.01601 11.73 672.0 942.0 37.23 25 42 434.6 581.0 .4006 .01576 11.81 ' ' 683.9 960.0 AC/AP 6 Pm Pd P0 11 average at 48.2 CC cm3 01113 cm3 Debye .———_._ 0.01592 1.005712 50.21 14.69 35.52 1.37 37. Table XVI Calibration with Ammonia for PentafluorOprOpionitrile (3rd determination) Pressure .AP Precision Standard .AC AC/AP cm. in Hg cm. in Hg Condenser Condenser uuf .uuf/cn. . . 67 .0 29 86 16.73 495 4 5 0. 2505 0.01497 13.13 651.4 912.0 . . 66 .0 30 41 18 18 491 2 9 32653 01459 12.23 ' 657.6 920.0 . 66 .O 32.41 19.64 487 3 3 .2949 .01502 12.77 672.5 _ 942.0 6 c AC/AP (6 - 1)x18 9 average at 47.2 C “A; “n.1,. .__ 0 .01486 5250 21 3.2 ‘ 38. Table XVII PentafluorOpropionitrile (3rd determination) Pressure 41’ Precision Standard 4C AC/AP cm. of Hg on. of Hg Condenser Condenser mf Raf/cm. 29.90 545.3 752.0 1 .17 2917 0 . 01522 10.73 _ 9 733.2 1028.0 0' 30.04 17.40 526.7 724.0 . 2653 .01525 12.64 695.4 975.0 11.79 705.0 989.0 ‘ACAAP 55 Pm Pd Po 7 average at 47.2 0C 0.3 cm3 0:3 Debye 0.01526 1.005439 47.66 14.69 32.97 1.32 39. Table XVIII Calibration with Ammonia for 2-Trifluoronethylpr0pene (1st determination) —' Pressure AP Precision Standard AC AC/AP on. of Hg 0:. of Hg Condenser Condenser an: .uuf/cl. w6. 228.3 224.0 3 53 26.35 0.4059 0.01540 10.18 451.9 608.0 39.27 207.4 186.5 2 . 6 .4603 .31537 9.31 9 9 460.8 622.0 37.91 29.04 ”0'9 ”1'0 .4408 .01518 8.87 464.6 628.0 — _ 7 0. 38.08 28.77 215.2 20 0 .4344 .31509 9.31 454.0 611.0 r _ . 18400 . 31.94 29.32 206 3 .4429 .01511 8.62 449.0 603.0 AC/AP (e- l)x106 Ce average at 31.4 °C 40%; __ 0.01523 5778 20032 40. Table XIX 2-Trifluoromethylpropene (lst determination) ~W Pressure AP Precision Standard AC AC/AP cm. of Hg cm. of Hg Condenser Condenser mt par/on. 6. '- 0 O 3 4’ 27.46 205 4 183 0 1.0063 0.03665 9.01 810.4 1135.0 38.53 144.7 79.0 , 1.1172 «03696 8.33 30 23 810.9 1136.0 39.16 29.53 109-5 16'0 1.0898 .03683 9.36 746.7 1047.0 AC/AP e P. Pd P0 11 average at 31.4 0C 0113 0113 cm3 Debye L — 0° 03681 1.01397 115.4 14.33 101.1 2-25 T 41. able XX Calibration with Annonia for 2-Trifluoronethylpropene (2nd determination) _A___ —vv 0.01583 Pressure (AP Precision Standard .AC AC/AP CI. of Hg on. of Hg Condenser Condenser lung ,uufi/cm. 735.64 194.0 164.0 V 25. 9 .3911 0.01540 10.25. 3 406.3 534.0 0 37.68 189.4 154.0 6 0 60 8.89 28°79 441.7 592.0 *4 3° ' 1 8 38.45 204.3 181-0 31 6 11.04 27‘41 438.0 587.0 '*291 r 5 5 35.03 239.3 243.0 816 01580 10.87 24°15 449.5 604.0 '5 ' 35.19 246.5 257.9 9.38 25.81 475.0 644.0 ~4O91 .91585 33.76 ' 268.4 297.0 01 1 9,59 94°17 480.6 661.0 ’3847 ° 59 b 0 410/42 (6- 1 >310 0 average at 30.0 C .u44£ f 5823 206°6 42. Table XXI 2-Trif1uoronethylpropene (2nd determination) Pressure on. of Hg. 0:. of Hg Afl’ Precision Standard AC Condenser Condenser uuf AC/AP “Hi/cm. 36.05 148.0 “I 84.0 _.____- 26.05 8.19 27'87 819.6 1147.0 '11? '33989 40.10 153.4 94.0 1 226 ) 950 9.06 31°04 898.8 1254.0 ° ° 3 37.50 213.4 197.0 . .3 8 10.64 26‘86 866.1 1210.0 1 071 39 7 37.22 216.8 203.0 1.100 .34000 9.74 27'48 891.4 1244.0 ;;_.,n_' . _ __: , - -47‘ 5' """r ZSCAQP 6. Pa PO u average at 30.7 0C on} 013 cm} Debye 0.03978 1.01464 121.53 14.33 107.20 2.31 ._ v __ _ _4, A .1 —- 43. Table XXII Calibration with Ammonia for 2-Trif1uoromethylpr0pene (3rd determination) 4 ___.‘ _ _ A ‘_- _‘ Pressure AP Precision Standard AC AC/AP cm. ong cm. of Hg Condenser Condenser uuf Auf/cm. A ‘ __.- —- 33°92 24.33 146'1 81'0 0.3615 0.01486 9.59 340.6 423.0 m" M 1.]. 02‘— 2 .0 38 62 28~95 4 3 .4323 ,01493 9.67 345.8 432.0 36.55 134.2 60.0 - .3974 .01488 9.85 26 70 347.7 436.0 ' . 16.0 35.07 23.46 165 5 l .3509 .01496 9.61 355.4 448.0 35'12 26.05 153'8 95'0 .3911 .01501 6 n 4011? (6 - 1)x10 60 average at 32.1 °C «4.; 0.01493 5753 197.36 v7 r—v rv 44. Table XXIII 2-Tri fluoromethylpropene (3rd determination) 1 Pressure AP Precision Standard AC AC/AP on. of Hg cm. of Hg Condenser Condenser uqf mf/cm. 34.89 216.1 202.0 10.77 24°12 822.8 1151.0 1~'OO3 0-04158 37.06 6 17O°8 125'0 1 117 04168 10.26 2 '80 845.1 1182.0 ' ' * .9894 .04159 10.54 23°I9 860.8 1203.0 AC/AP E P]; Pd PO u average at 32.9 00 cm3 cm} c113 Debye ¥ — v-‘v- 7" y '_ v-vwv 0.0416914714010073 134.20 14.33 119.9 2.45 ww— — - ..-- w—w ”WI. fiawww _‘_ .... , 'v w... . r ' 'IL—v 45. Table XXIV Calibration with Ammonia for PentafluorOpropionyl Chloride (lst determination) ——— fiessure AP ' Precision Standard AC ACZAP cm. of Hg cm. of Hg Condenser Condenser Ann; “Hf/cm. 33‘72 ‘ ' 488.4 665.0 21°41 0. 06 0.01432 12.31 680.6 955.0 -5 5 36.28 466.8 632.0 23.37 . 277 .01402 12.91 672.2 942.0 3 .5 "5575555 55‘ . 5 610.0 57'06 25.48 455 4 3530 .01382 11.58 673.4 944.0 ..n,,,-m.. . 61 .0 0 35.77 24 9? 454 7 3 .3562 .01429 10.85 ’ ‘ 677.0 950.0 34.29 22.47 “7'7 648'0 .3277 . 31458 11.82 683.4 958.0 30.82 18 98 520.6 715.0 .2833 .01492 11.84 ‘ 700.6 983.0 33.58 21 00 500.1 683.0 ‘5171 ,31510 12.58 ' 701.0 983.0 33.98 ?2.99 504-5 590‘0 .3213 .01398 10.99 709.0 994.0 -FmL—”’V5 440762 (6- 1)x106 Co average at 47.500 444‘; ... 0.31438 4950 220.78 46. Table XXV PentafluorOprOpionyl Chloride (lst determination) _h 1‘ Pressure AP Precision Standard AC AC/AP on. of Hg cm. of Hg Condenser Condenser 1111f uuf/cn. ...L‘ __. ...— __ ’ . 0 .0 35°59 24.31 513 6 7 4 0.3108 0.01279 11.28 711.2 998.0 34.93 560.6 776.0 - e O 02 0312 7 10.88 24 05 756.9 1062.0 5 5 5 12.41 745.6 1046.0 35.57 23 64 557-2 770'0 .3002 .01269 11.93 ° 751.2 1054.0 P u AC/AP é PIll Pd 0 average at 48.0 00 cm3 cm3 on3 Debye k O.01270 1.004371 38.38 19.68 18.70 0.991 -..;- __ ' Y7 47. Table XXVI Calibration with Ammonia for Pentafluoropropionyl Chloride (2nd determination) Pressure AP Precision Standard AC AC/AP cm. of Hg cm. of Hg Condenser Condenser Inn! nut/cm. #— -_ .' .0 32.68 20 00 355 6 448 0.2928 0.01464 1.2068 5 52700 72500 35.59 313.6 377.0 . . 358 .01 27 12.12 23 47 521.1 716.0 ° 3 5 .0 407.0 _ “‘86 22.12 331 .3308 .01499 12.74 524.5 720.0 6 AC/AP (6- 1)xlO Co average at 45.6 °C ,q4+{ 0.01495 5305 214-2 __~ —‘__ 48. Table XXVII Pentafluoropropionyl Chloride (2nd determination) wfi“—- Pressure A P Precision Standard A C AC/A P cm. of Hg cm. of Hg Condenser Condenser “at“ turf/on. 34.33 387.0 503.0 . .2822 0.01273 12.24 22 09 557.0 770.0 0 11.51 593.8 825.0 . 8.0 35.18 24.56 420 2 55 .3034 .01235 10.62 607.6 845.0 A 5.0 91.0 33.71 22 31 441 5 .2769 .31241 11.40 ° 612.8 853.0 10.37 25°87 635.0 887-0 AC/AP 5 P. Pd . “ average at 46.3 °C om5 cm3 cm3 Debye 0.01253 1.004446 38.81 19.68 19-13 1°00° w. _ 49. Table XXVIII Calibration with Ammonia for Methallene (lst determination) — j Pressure AP Precision Standard AC AC/AP cm. of Hg cm. of Hg Condenser Condenser 1411f mf/cm. 34°73 24 27 208'6 189.0 0 3816 (101572 10.46 ° 415.4 550.0 ' ’ 35.89 25 43 212.1 194.0 .4017 .01579 10.45 ° 430.1 574.0 .3 1 6.0 38.09 26.84 212 1 9 .4091 .01524 11.25 436.0 583.0 37.12 26 90 225°2 214'0 .4122 .01532 10.22 ° 449.2 604'° 35.98 24.83 234-1 254'0 .3795 . 01528 11.15 441.8 593.0 12.11 ' 431.4 576-0 5541.01549 5760 204" v— - .4 A ' 50. Table XXIX Methallene ( lst determination) Pressure AP Precision Standard 410 AC/AP cm. of Hg cm. of Hg Condenser Condenser 1m! Rut/cm. —. ‘31-.» but‘ v— ——_——— 36-56 22.6., 187-4 152°C 0.1659 0.007318 13.89 275.3 309~° 37.91 25 02 183.0 146°C .1881 .007518 12.89 ° 283.2 324-0 , . 1 6.0 37.17 23.68 189 2 5 .1786 .007542 _ . 180.0 34.11 21 11 202 8 6 0 .1549 .007812 13.00 ‘ 289.2 55 ' 410/42 6. P. P6 Po “ average at 33.0 °C cma cm3 cm3 Debye ”0*- 0-007548 1.002807 23.49 19.68 3.81 0.43 l- J __ ‘ 51. Table XXX Calibration with Ammonia for Methallene (2nd determination) ——fi_f Pressure AP Precision Standard AC AC/AP cm. of Hg cm. of Hg Condenser Condenser uqf an/cm. _ r—x—r 33.07 225.0 218.0 . .29 8 0.01 13.48 19 59 384.9 496.0 0 3 499 35.16 194.8 166.0 03467 e0 12°12 23'04 381.8 494.0 1504 35.60 200.0 174.0 22.64 . O .31 12o96 389.8 508.0 555 559 -6. 0 204.3 182.0 12.66 405.9 534.0 35.55 5555 210.5 192.0 266 .01542 14.37 21°18 386.4 501.0 -5 6 Ac/AP (e - 1)xlO 09 average at 33-6 °C «14.; 0.01533 5700 204-4 ‘7' ——- ‘1 Methallene (2nd determination) 52. Table XXXI Pressure zAP Precision Standard .AC AC/AP cm. of Hg cm. of Hg Condenser Condenser Ant“ Ruf/cm. . 10 . 36.95 23.55 159 1 4 0 0.1807 0.00767 13.40 256.2 275.0 . _ 41H"-1”M1_m12_ .0. 39.60 25 77 155-0 99 .1903 .00735 13.83 ° 258.4 279.0 35.68 -3 40 134.0 59.0 .1755 .00750 12.28 ‘ ' 229.1 225.0 410/42 6 P. Pd P0 “ average at 33.7 0C cm5 cm3 cm3 Debye 0.00751 1.002792 23.44 19.68 3.76 0.435 - -..-'4 b .‘— w-..'- “..-dm‘.-. .413 "en-”W __ ”A. - ‘31. . v_'- .1 53. Table XXXII Calibration with Ammonia for PerfluorOpmpylene ; — >-n‘a"-.l-O---.‘—- -..“.o.‘ “m.“ ,, ......”- -_ __ __ ___ . _ - Pressure QP Precision Standard LC 4.0/AP cm. of Hg 0:11. of Hg Condenser Condenser uuf nuf/cm. ~ -.-“-_~_——_. --4—fl 27.72 186.6' 152.0 14.20 15°52 290.4 344 0 0.20294 (101501 43-17 182.1 144.0 25.39 6' 5 e -80e0 4 77 27.98 433 9 b .3953 .01413 18.79 680.1 954.0 . O 0.0 44 59 - 28.50 540 O 59 .4249 .01491 16.09 707.2 992.0 44-29ufimfiwwmwflfiu 5 439.5 590.0 28.41 .4376 .01540 15.88 715.9 1004.0 6 2.0/21? (5 - 1))é10 00 average at 77.6 C 1.1.2.4" 0.01509 4460 257.1 54. Table XXXIII Perf1u0r0pr0py1ene u- “nu-......o-m. w o. v-— .— ~.-‘-n-— *— A‘ — Pressure 132 Precision Standard 40 40/42 cm. of Hg dm. of Hg Condenser Condenser ,quf uni/cm. --m-- -—~——--.'-‘ -- I -..-o—fi-rw-Wnrmnw Tww 51.44 583.8 810.0 0 4006 0 00980 10.58 40'86 850.3 1189.0 ' ° ‘ I O 6 O 0 51°44 41.96 555 8 7 9 .4302 .01025 9.48 840.8 1176.0 50.57 41.34 426.6 569.0 .4143 001002 9.23 685.6 961.0 60/62 6' P Pd Po u average at 77.500 3:3 cm3 cm3 Debye (101002 1.002962 28.41 7.026 20.82 1.11 Calibration with Ammonia for Sulfur Tetrafluoride 55. Table XXXIV (lst determination) Pressure AP Precision Standard A C Q C/a P cm. of Hg cm. of Hg Condenser Condenser Airf ,uuf/cm. 29.95 512.6 702.0 _ 5 - 0.2600 0.01565 13.35 “’50 676.2 948.0 28.20 524.4 748.0 . .2114 .01471 13.83 14 37 676.3 948.0 28.12 15.54 536.8 740.0 .2410 .01551 12.58 689.8 968.0 .' . .0 5O 50 19 05 521 6 716 .2843 .01493 11.55 5 702.0 985-0 29.13 16 22 539.8 745.0 .2463 .01519 12.91 ’ 696.9 978.0 6 nc/AP (e — l)x10 C average at 47.000 “8f 0.01520 5260 219-5 —"' 56. Table XXXV Sulfur Tetrafluoride (lst determination) Pressure .1? Precision Standard. 10C éc/AP cm. of Hg cm. of Hg Condenser Condenser N‘f Raf/cm. 37.34 25.74 632.3 882.0 0.2389 0.009289 11.60 789.6 1108.0 37.42 26 10 539.8 745.0 .2357 .009031 11.32 ' 689.9 968.0 ”'65 26.12 537'4 “0'0 .2304 .008821 11.53 683.2 958.0 . ___ 0.0 3!.11 25.61 537.4 74 .2325 .009078 11.50 683.8 960.0 "C/AP e P Pd Po ‘1 average at 47.00C 0:5 cm3 0[13 Denye 0.009055 1.003134 27.45 11.7 15-75 0°91 - - .-_§.-----u.‘.-W" _-._--‘ -—-* “.-.-M ~ __ ”...-..-“; —-..-—-T—Eg-_~'.' '2‘. ..IL.‘.:-;.'._ C) 57. Table XXXVI Calibration with Ammonia for Sulfur Tetrafluoride (2nd determination) -_-...... _. ........._.. .— -..- ..mp— -.— -—..—- Pressure [\P Precision Standard 430 AC/AP cm. of Hg. cm. of Hg Condenser Condenser RH; .mui/cm. .2 8. 618.0 23 2 11.31 45 5 0.1702 0.01505 11.91 562.9 779.0 . ”55M555 8. 617.0 25 38 14.83 45 3 .2251 .01517 10.55 597.2 830.0 2.. 2' "“ " . .0 2 13.60 “6‘5 630 .2029 .01492 12.62 592.4 822.0 , - 6 .1‘1C/j1P ( t — 1))(10 CO average at 46.9% Wf 0.01505 5263 217.3 .... '—~o.wm_.. 58. Table XXXVII Sulfur Tetrafluoride (2nd determination) _ -_—__.. .--—— .._-.. ... -—.-— v c ., “—h_...w-.- -"F .4 —---'v..-.—___. - - .—-—_ _‘_ Pressure A P Precision Standard A C AC/AP cm. of Hg cm. of Hg Condenser Condenser nuf Auf/cm. . 08.2 695.0 32 39 21.28 5 0.1966 0.009239 11.11 630.6 881.0 33.28 504.3 689.0 22. .2093 .009265 10.69 59 635.0 887.0 33.65 21.23 513-8 704°C .1945 .009162 12.42 636.0 888.0 410/42 6 P Pd Po ‘1 average at 47.20c 0:3 cm3 cm3 Deoye 0.009222 1.003229 28.29 11.7 16.59 0-93 o-«r —.. -... _ ~ “- “H.v~- * The SF co dipole4 moment of 1.62D. to the average value of SF4, was .88D. ntained abou See page 24. t 5% impurity of SOF After applying th ”-..... a .-#_‘ which has a £5 correction the dipole moment of SF4 59. Table XXXVIII Moments ----.-~- ~“W'.-’J_.-..H.¢~_.w “...—-.L.‘ _ M.“ ..w..—“ __; COMPOUND Ethyl Acetylene Vinyl Methyl Ether A...“ —-——---- ..— m—w ‘— A . -..-...- __ PentafluoroprOpionitrile 2-Trifluoromethylpmpene PentafluorOprOpionyl Methallene PerfluorOpropylene Sulfur Tetrafluoride Chloride Dipole noment,D Error,D 0.76 10.1 1.06 .l 1.33 .l 2.34 .l 0.99 .l 0.44 .1 1.11 .2 0.88 .2 ... _. .... —_.—...—-——.— 60. Discussion of Error The most probable error in the replaceable capacit- ance can be obtained by differentiating equation (41) thereby obtaining, d3 , ——O_ . ELI-Lg + £3 CIA/H3 m, Since the beat frequency could be determined within about 1 ops, the value of dAC was aboutclool uuf. 6 - 1 for ammonia was about SOOOxlO"6 and de for ammonia was about 10-6. Then by using the value ofzfic for ammonia, the Quantity dCo was obtained from the above equation. Since the replaceable capacitance was about 210 uuf, the error in determining it was about 7%. To determine the maximum error in the dielectric constant of the material under investigation, differentiate equation (42); thus, de .-. d("--C//\P 76) 76 ACjAP dC a + 2 o “J c O ' O Again,using the value¢fi‘LLOOl for the error in the slope and the error in the replaceable capacitance as obtained above, the error in the measurement of the dielectric constant can be determined. By differentiating equation(43), the error in the molar polarization is obtained from, dill] : dé 2,. (iv P! E:- l Vn Since it was assumed that the :ases investigated were behav- ing ideally, and since this is not really accurate, an error 0f about 0.1 in VI was assumed. 61. Since this method of investigation does not take into account atomic polarization, the error in Pd was assumed to be about 10%. Thenjby differentiating equation (44), the error in the orientation polarization was determined by, dP0 a dP.+ de Finally, the error in the dipole moment was determined by differentiating equation (45) to give, dP dT $3 = ..2. ____. 11 2P0 + 21' The second term in this equation however was negligible in comparison to the first since the temperature variation amounted to only aboutOtl of a degree. When this method was applied to the compounds measured in this investigation, the maximum probable error was as follows: Compound u .Au CFBCF2CN 1.33D 1 .10 CFBCF-CF2 1.10 1 .2D CF3"?”CH2 2.34D i‘.2D CH3 CFBCF2001 0.990 t .lD CH30H2C§CH 0.76D 1 .2D CH300H3082 1.06D ‘1 .20 0H30H=C=CH2 0.441) t .4D SF4 0.88D 1' .21) The error involved seems to be quite large; however, the fact that the replaceable capitance was determined in dielectric constant of the compound the same manner as was the On this under investigation causes the error to be minimized. basis, reporting the error as .11) for all of the compounds except CFBCF=CF2 and SF4 is reasonable. Due to the fact that SF4 has such a large atomic polarization, the error involved is about .2D. The perfluorOpmpylene must also be reported as about .21: since its dipole moment was determined only once. IV. DISCUSSION A dipole moment can yield valuable qualitative inform- ation about the structure of a molecule. Of special importance are the magnitude and direction of the moment since with this information one can compare a measured moment with the moments of similar compounds and thereby interpret changes in terms of differences in electronic environments. The interpretation can be based on resonance theory or on the classical theory of in- duced dipoles. In terms of resonance, each structure can be thought of as contributing to the state of the molecule. Furthermore, structures with formal charges on them may be expected to con- tribute heavily toward the net moment of the molecule even though these structures may make only a small contribution to the state of the molecule. The particular type of resonance referred to in this investigation is hyperconjugation. This Can be described by structures such as, CH30H=0H2 G—m CH280H-CH H4- Resonance energies due to hyperconjugation are usually of the 2 order of 3 or 4 kcal/mole as measured from heats of hydrogen- ation. Hence, the hyperconjugated structure probably makes only a small contribution to the state of the molecule. How- ever, as stated above, this small contribution may give rise to a large dipole moment. This seems to be especially true of molecules containing the CF3 group. Further evidence of hyper- conjugation has to do with the shortening and lengthening of bonds. For example, if propylene can be represented by hyper- conjugated structures, one would expect a shortening of the C(sp3)-C(sp2) bond and a lengthening of the carbon-carbon double bond. Microwave and electron diffraction measurements on bond distances seem to indicate that this is what occurs. 63. 64. Classically, one might be able to account for variations in dipole moments by inductive effects. This effect may tend to increase or decrease the net dipole moment depending on the type 3Cl; the chlorine is more electronegative than the carbon atom , and of molecule. For example, consider the molecule CH hence the bonding electrons in the C-Cl bond are shifted toward the chlorine atom. This leaves the carbon atom positive relative to the chlorine atom. Hence the carbon atom tends to attract electrons from the hydrogen atoms, and thus a dipole is induced in the direction 8:5: In a molecule such as CF3Cl, the fluorines are more electronegative than either the carbon or chlorine atoms. Therefore the bonding electrons in the C-F bond are shifted toward the fluorine atoms thereby leaving carbon positive relative to fluorine. Hence the carbon atom pulls electrons in the C-Cl bond toward itself, thereby inducing a moment in the C-Cl bond, so as to oppose the principal moment in the C-Cl bond. It is rather difficult to calculate an induced moment since the exact location of the electrons in the bond is unknown. However, the magnitudes are usually about 0.1 to 0.2D. From a standpoint of'interpretation,the direction of the induced dipole is the important thing. Nuclei, as well as electrons, can be displaced from their equilibrium positions so as to create an atomic dipole. This is especially true of molecules containing atoms with unshared electron pairs. When an unshared pair occupies an s or p, or any orbital-in which the associated center of negative charge is coincident with the positively charged nucleus, an atomic dipole will not occur. Hence, an atomic dipole can exist only if the atomic orbital is a hybrid. The magnitude of such moments could be very large depending on the distance of the unsnared pair from the nucleus. Moments may also arise due to the differences in the electronegativity of carbon atoms in different states of 650 hybridization. Hence the moments of the C(sp3)-C(sp2) bond, the C(sp3)-C(sp) bond, and the C(sp2)-C(sp} bendsare not zero. The actual value of these moments are difficult to determine, but the direction would be toward the more electronegative or more unsaturated carbon, (8). In order to calculate approximate values for the dipole moment so as to make comparison with experimental quantities, one usually assumes that the molecule can be represented by a vector model, the resultant vector being the vector sum of the individual bond vectors or bond moments. The bond moments used to calculate the dipole moments of molecules in this investigation are: CF in CFBH 1.2D C01 in 011301 1.51) CN between 2 and 2.5 D C-O in (CH3)O 1.5D C-H 0.4D The direction of the C-H bond moment was according to (9). - 04181)} )-H _ .+ C(sp2)-H - -+ C(sp) -H be. 2-Trifluoromethylpropeng_ The dipole moment was measured as 2.33D. The value calculated from bond moments is much less than this figure, about 1.5D. However, a comparison of this compound with other compounds containing the trifluoromethyl group is in good agreement. It is to be noted that compounds with the CF3 group exhibit very large dipole moments. This is attributed to the extremely high electron withdrawing power of the group. For example, CF3CCl=CCl2 has a dipole moment of 1.28D and CFBCF=CF has a dipole moment of 1.1D. Both of these compounds would be 2 expected to have very small dipole moments. The large moments seem to imply that some sort of hyperconjugation of the CF3 group is occurring. Since the CF3 group is extremely electron withdrawing, it would be expected that the sp2 carbon would be polarized so as to induce a moment in the direction of the trifluoro- methyl group. Such an effect could probably be represented by structures such as. The effect of the methyl group, which might also undergo hyperconjugation,shou1d be to decrease the moment. A comparison with CF CH=CH2,2.45D, shows that this is exactly 3 what happens. Perfluoropropylene The dipole moment was found to be 1.1D. One would eXpect a very small moment for this compound by comparison with CH3CH=CH2, 0.35D, and 0013c013c012 , 0.4D. Evidently, the 67. type of hyperconjugation previously described for 2-trifluoro- methylpr0pene is also significant in this compound. Hence, snructures such as the following may account for the large large moment observed: F C F F‘ gait“ 'E/' /" b \ F F PentafluorOpropionitrile The dipole moment was found to be 1.33D. It is difficult to calculate the dipole moment of this compound since no suit- able bond moment for the GEN bond is availible. That is, the value varies with the environment of the cyanide group. For 3 the value would be about 3.5D. This is due to the fact that the overall moment of these compounds is due to resonance example, in HCN the bond moment would be about 2.5D; in CH CN structures of the type: . - + - HCN 4» H-C:N a H OH H? C CN H CH ‘ C=N HBCN HCHBC=N H CH3 2 Clearly, the hyperconjugated structure in CH CN would have no analog in CFBCFZCN due to the large electronegativity of F, and therefore there would be no justification for using the value 3.5D for the bond moment of CN. Similarly, the ionic structure in HCN has no analog in CF30F2CN. On this basis, it is not expected that the CN bond moment will make such a large contribution to the moment of CFBCF2CN. The CN moment will then be due to a resonance structure such as, CF CF 3 N’ 32" However, due to the large electron withdrawing power of the CF3CF2 group, structures such as, CFBCF = C :'§ F 68. will also contribute heavily toward the overall moment. The direction of the resultant moment would probably still be to- ward the cyanide group. PentafluoroprOpionyl Chloride The dipole moment was measured as 0.99D. The calculated value, based on the bond moment of C = O in phosgene and the I bond moment of C-Cl in CHSCl, was about 1.35D. The lowering is accounted for by the large electron withdrawing power of the CF3CF2 group. The sp2 carbon will be polarized by the CF3CF2 group so as to induce a moment in the direction of this group. In terms of hyperconjugation, this effect can be represented by structures such as, o cr3cr -.- cf ‘c1 r Methallene The observed moment for methallene in this investigation was 0.44D. This value agrees extremely well with the value 0.401D determined by microwave spectroscopy (10). The value calculated on the basis of bond moments is about 0.8D with the resultant vector toward the methyl group. However, this value does not take into consideration a dipole contribution from hyperconjugation. By examining the direction of the moment in the follow- ing two compounds, it can be shown that the direction of the 69. moment in methallene is toward the sp2 carbon rather than toward the methyl group; 1 II n c__ H 11‘ H -3 C : C/ (C 3 Cf" H'” \c1 1130' “Cl “exp.' 1.970 uexp.= 1.710 If the direction of the CHB-C moment was toward the sp3 carbon, compound 11 would be expected to have the larger dipole moment; experimentally, compound I has the larger moment. This indicates that the CHE-C moment is in the direction of the sp2 carbon. This also implies that hyperconjugation of the type, CH2 2 CH - C : CH2 H+ is occurring. Evidence for hyperconjugation in methallene is supported to some extent by the shortening of the C(sp3)-C(sp2) bond length by about .06A (10). Furthermore, compounds of this type exhibit resonance energies of several.kiloca10ries per mole as obtained from heats of hydrogenation data. Ethyl Acetylene The dipole moment of ethyl acetylene was determined as {).76D. This agrees well with the value previously determined, (3.809 (11) by a heterodyne-beat method. The value calculated on the basis of bond moments is about .8D in the direction of the ethyl group. Not included in the calculation is a polar contribution due to hyperconjugation. Sucn a contribution can be represented by structures such as, c - c CHBUH «- v H*- 6h 70. The hyperconjugation would be of sufficient magnitude to give a resultant moment in the direction of the acetylenic carbon. Vinyl Methyl Ether The dipole moment of vinyl methyl ether was determined to be 1.06D. The value calculated on the basis of bond moments is about 1.8D. A comparison of methyl ether, 1.29D, and vinyl ether, l.O6D suggests that the moment of vinyl ether is low- ered relative to methyl ether by structures such as (12), ”-+ - CH2= CH-O=CH-CH2 Similarly, one would expect the moment of vinyl methyl ether to be decreased by structures such as, , + " CH3-O=CH-CH2 Hence, a consideration of resonance would tend to lower the calculated value to some extent therby making the experimental value of 1.06 quite reasonable. The resonance effect can be supported to some extent by heats of hydrogenation data (13) of similar compounds. The resonance energies obtained by this method for vinyl ether and ethyl vinyl ether are 3.4 and 3.0 kcal/mole respectively. Sulfur Tetrafluoride The dipole moment obtained in this investigation was 0.88D. This compares fairly well with the value of 1D obtained by anather heterodyne-beat method (14). However, the value has been determined quite accurately by a microwave technique as 0.64D (15). The rather large difference between 0.85D and 0.64D is indicative of a large atomic polarization which was not taken into account in the present work. 71. The fact that SF4 has a dipole moment immediately rules out structures utilizing hybrid orbitals which give planar and tetrahedral arrangements since they would have dipole moments of zero. The NMR spectrum of SF4 shows two peaks with a chemical shift of 1920 cps, each peak being split into a triplet of equal intensity.(lb). Hence, two pairs of chemically different fluorines are indicated. This would be consistent with a trigonal bipyramid with the unshared pair in an equa- torial position. The fact that the molecule has a dipole moment supports this structure. The hybridization would probably be sde with the unshared pair occupying a hybrid orbital. Hence the unshared pair would give rise to an atomic dipole which would contribute to the net moment of the molecule. This,too, is to be expected since the net moment is comparimively small, and since the large electronegativity difference of S-F, 1.5, indicates a rather large moment for the S—F bond. 72. Bibliography 1. J.H. Van Fleck, “The Theory of Electric and Magnetic Sus- ceptibilities", Oxford University Press,London, 1932, pp.32. 2. P. Deybe, "Polar Molecules", Chemical Catalog CO., New York, N.Y., 1929. 3. C.P. Smyth, "Dielectric Constant and Molecular Structure", Chemical Catalog CO., New York, N.Y., 1931. 4. R.D. Pruett, Ph.D. Dissertation, Michigan State University, 1954, pp.24. 5. J.A. Conner, Electronics, 23, 250 (1951). 6. "Handbook of Chemistry and Physics", Chemical Rubber Pub. CO., i i Cleveland, Ohio, 1957, Ed.59, pp. 2425. (m; 7. R.L. Burnwell, A.H. Peterson, and G.B. Rathmann, Rev. Sci. Instr., 12, 608 (1948). 8. 3.3. Mulliken, J. Chem. Phys., film 318 (1937)- 90 VOL. Gent, Quart. RGVSO, 2., 583 (1948). lo. D.R. Lide and D.E. Mann, J. Chem. Phys., 21, 874 (1957). 11. F.J. Krieger and H.H. Wenzke, J. Am. Chem. Soc., 99, 2115 (1938). 12. C.P. Smyth, "Dielectric Constant and Molecular Structure", Chemical Catalog CO., New York, N.Y.,1931, pp.298. 13. G.w. Wheland, "Resonance in Organic Chemistry", John Wiley and Sons, Inc., New York, N.Y. 1955. pp-BS. 14. R.E. Dodd and R. Little, Nature. lfifi. NO- 4752: 737 (1960)° 15. W.D. Gwinn and w.M. Tolles, University of California, Berkeley, Unpublished Results. 16. F.A Cotton, J.w. George and J.S Waugh, J. Chem. Phys., 2Q. 994 (1958). CHI-TM YSTRY LIBRA HY NOV 2 2 '81 MICHIGAN STATE UNIVERSITY LIBRARIES l ill 3 1293 030713758