THE EFFECT OF SODIUM SULFITE ON THE ULTRAVIOLET ABSORPTION SPECTRA OF VARIOUS BENZENE DERIVATIVES By GRANT MILFORD HAIST ",v A THESIS Submitted to the School of Graduate Studies of Michigan; State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1949 ACKNOWLEDGMENT The author wishes to express his sincere gratitude to Daator D. T. Ewing, Professor of ^Physical Chemistry, for his guidance and as­ sistance throughout the duration.of this work. The author is also indebted to the Trustees of the William and Sarah E. Hlnman Scholarship Fund for the grant of a Fellowship which aided in the continuation of this work. INTRODUCTION In the course of a spectrophotometric Investigation of the exhaustion of various photographic developing agents, it was observed that a bathochromic shift in the ultraviolet absorption spectrum of hydroquinone occurred upon addition of sodium sulfite. Shifts in ultraviolets absorption spectra, especially those not involving the additions of auxochromes to the resonating system or chem­ ical combinatiombetween the solvent and the? compound, have received increasing? attention iin recent:, years• Stenstrom and Reirihard1 found that benzene deriva­ tives with a ring hydroxyl group, such as phenol, tyro­ sine or resorcinol, gave a shift to longer wave lengths upon addition of alkali. The band characteristic of- the molecule shifted towards longer wave lengths and increas­ ed in intensity w h e m a certain alkalinity had been: reached. These investigators attributed the shlftt to: the change from the spectrum characteristic of the molecule to the spectrum characteristic of the compound ionized atr the ring hydroxyl group> In agreement I.with the effectt of alkali on phenol, Morton and Stubbs2 found that the absorption spectra of hydroxyaldehydes, hydroxyketones, and their methyl ethers, when studied in alkaline solution, show.a bathochromic -1- displacement of the long wave band. Since a change in the initial energy state is indicated by this action, they observe that it must be the result of the Induction effect of the substituents on the ring. More recently, in 19^7» Lemon^ studied the effect of alkali on the ultraviolet absorption spectra of hydroxyaldehydes, hydroxyketones, and similar phenolic com­ pounds. He found that the absorption bands of all these compounds were shifted towards longer wave lengths and, with the exceptioh of m-hydroxybenzaldehyde, the intensity of light absorption was increased. Although all the or­ tho, meta, and para hydroxyaldehydes and hydroxyketones show spectral displacements in alkaline solution, it was the p-hydroxyaldehydes and the p-hydroxyketones that show the greatest wave length displacement of the long wave length, bands and the greatest Increase in absorption in­ tensities. Doub and Vanderibelt^ studied the ultraviolet absorp­ tion spectra of mono- and para^- disubBtituted benzene de­ rivatives.. From these studies they formulated a general rule applying to such compounds: “Where ionization of a groupattached to a benzene ring enhances the already ex­ isting tendency for electron transfer to or from the ring, the maximum of the primary band is shifted to longer wave, length; where ionization diminishes this tendency, a shift to shorter wave length results." However, environmental conditions may produce spectral changes without involving changes in molecular structure, such as the ionization-mentioned above. Klotz^ investiga­ ted the effects of salts on,the absorption spectra of var­ ious dyes and indicators. He found that although:the ef­ fect of salts can be attributed largely to electrostatic interactions of the Debye-Huckel type, many specific inter­ actions are found. These interactions are of the ion-di- pole attraction.type of the electrolyte with the solvent molecules. Further, effects of electrolytes in aqueous solution were studied by Merrill, Spencer, and Getty^ and Merrill and Spencer^. In their investigation of the effect of. sodium silicate on: the absorption spectra of various dyes, they found spectral, changes not due to,the alkalinity of the silicate but attributable to sorption: and electro­ static interaction of the dye ion with the sodium silicate ions • It is the purpose of this investigation to study the bathochromic shift of the absorption spectra of hydro>qulnone and related compounds upon the addition of sodium sulfite and to characterize the sulfite effect. EXPERIMENTAL PROCEDURE Absorption measurements were made with a Beckman Quartz Spectrophotometer, Model DU®. The absorption cells were made of silica,.the thickness of each being 1.000 I 0.001 centimeter. The extinction readings were taken at intervals of 5 millimicrons, except in a few cases in the vicinity of absorption spectra maxima where the interval was 2 millimicrons. The solvent in all cases was water. Laboratory dis­ tilled water was redistilled from all glass apparatus. The water was used as soon as possible to prepare the solutions to be run. A spectroscopic determination of the purity of the solvent indicated the absence of inor­ ganic impurities. The organic chemicals were of C.P. grade or better, most of them being Eastman.Kodak white label grade. Puro- hydroquinone and diaminodurene dlhydrochlorlde were ob­ tained from Dr. A. Weissberger of the Synthetic Organic Research Laboratory of the Eastman Kodak Company. Cumo- hydroquinone and p-xylohydroquinone were obtained from a private source at the same company. The inorganic chemi­ cals were also of C.P. quality or better, being in most cases either Baker's Analyzed or Elmer & Amend tested purity reagents. The" chemical or chemicals were accurately weighed out, placed in a thoroughly cleaned and dried volumetric flask, and then dissolved in the solvent. An.alternate procedure was to make up separate organic and inorganic solutions of such concentration that when combined the resulting solu­ tion is of.the desired concentration. The flask was then inverted and shaken vigorously,.this procedure being re­ pealed fifty times to insure complete dissolution of the solid material or mixing of the solutions. The repeated shaking is absolutely necessary in the case of the poly­ substituted hydroquinones and the polysubstituted pphenylenediamines to insure solution. After the shaking the absorption spectrum was then.determined on the spec­ trophotometer. -5- TABLE I Pig. Organic Compound (g*/ml«) Sodium Sulfite Concentration (g./ml*) Maximum Organic (m mu) Cone* Maximum Shift Ora* & Sulfite (m mu) (m mu) 1 Hydroqulnone 0*000045 0*000090 288 305 17 2 Pyrocatechol 0*000045 0.000090 275 275 0 3 Resoroinol 0*000045 0*000090 275 275 0 4 p-Amlnophenol hydro chloride 0*000045 0*000090 270 295 25 5 o-Aminophenol 0*000045 0.000090 285 285 0 6 m-Aminophenol 0*000045 0.000090 280 280 0 7 p-Fhenylenediamlne dihydroohloride 0*000045 0*000090 285 305 20 8 o -Phenyl enediamine 0*000045 0*000090 290 290 0 9 m-Fhenylenediamlne 0*000045 0*000090 285 285 0 10 Elon (Monomethylp-aminophenol sul­ fate) 0.000045 0*000090 270 300 30 Amidol (Diamlnophenol dihydro­ ohloride) 0*000045 0*000090 285 310 25 11 TABLE I (continued) Fig. Organic Compound Sodium Sulfite Concentration (g./ml.) (g./ml.) Cone. Maximum Organic (m mu) Maximum Org. & Sulfite (m mu) Shift (m mu) Glycin (p-Hydroxyphenyl glycin) 0.000046 0.000090 270 300 30 13 Phenol 0.000045 0.000090 270 270 0 14 Quinone 0.000045 0.000090 295 310 15 15 p-Cresol 0.000045 0.000090 275 275 0 16 D iacetylhydroquinone 0.000045 0.000090 260 260 0 17 p-Methoxyphenol 0.000045 0.000090 288 288 0 18 Sulfanilamide 0.000009 0.000090 260 260 0 19 D iaminodur ene dihydrochloride 0.000045 0.000090 270 270 295 0 25 20 Tetrachlorohydroquinone 0.000045 0.000090 305 328 23 21 Durohydroquinone 0.000020 0.000090 272 263 9 22 Cumohydroquinone 0.000020 0.000090 260 262 2 23 p-Xylohydro quinone 0.000045 0.000090 288 252 36 18 TABLE I (continued) Fig. Compound Cone. Inorganic Cone. (g./ml.) (g./ml.) 0.000090 (Sodium Sulfite) 24 Phloroglucinol 0.000045 25 Hydroquinone Sodium Bisulfite 0.000045 0.0001 0.000090 (Sodium Carbonate) 26 Hydroquinone 0.000045 27 Hydroquinone Cysteine monohydrochloride 0.000045 28 Hydroquinone 29 T etramethyl-pphenylenediamine dihydrochloride Maximum Maximum Shift Comnound Como. & Inora (m mu) (m mu) (m mu) 265 275 10 . 288 308 20 0.000090 (Potassium Sulfite) 288 300 12 0.0002 (Sodium Carbonate) 288 290 2 0.000045 0.0000225 0.000045 0.000090 0.000180 (Sodium Sulfite) 288 288 288 288 295 300 305 300 7 12 17 12 0.000045 0.000180 0.000090 0.000360 (Sodium Sulfite) 250 285 250 & 300 300 15 0.000090 2.00 Extlnotlon 1.60 1.20 Hydroquinone 0.60 0.40 0.00 220 240 260 280 300 340 360 360 400 Wave Length (millimicrons) Figure 1. A-Hydroqulnone (0.000045 g./ml.) B-Hydroqulnone (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 2.00 1.60 Extlnotlon OH 1.20 Pyrocatechol 0.80 0.40 0.00 260 220 280 300 320 360 380 Wave Length (millimicrons) Figure 2. A-Pyrooatechol (0.000045 g./ml.) B-Pyrooateohol (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 2.00 1.60 Extlnotlon OH 1.20 Resorclnol 0.60 0.00 220 240 260 280 320 360 Wave Length (millimicrons) Figure 3. A-Resorclnol (0.000045 g./ml.) B-Reeorolnol (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 380 400 2.00 Extlnotlon 1.6o nh2 1.20 p-Amlnophenol 0.80 0.00 260 220 280 300 320 400 360 Wave Length (millimicrons) Figure 4. A. p-Amlnoohenol Hydrochloride (0.000045 g./ml.) B. p-Amlnophenol Hydroahlorlde (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 2.00 1.60 Extlnotlon NH 1.20 o-Amlnophenol 0 .8 0 0.00 220 240 260 280 300 320 360 380 400 Vmve Length (millimicrons) Figure 5. A. o-Amlnoohenol (0.000045 g./ml.) B. o-Amlnonhenol (0.000045 g./ml.) Sodlim Sulfite (0.000090 g./ml.) 2.00 1.60 Extinction NH 1.20 m-Amlnophenol 0.80 0.40 0.00 220 260 280 300 320 Vmve Length (millimicrons) Figure 6. A. m-Amlnophenol (0.000045 g./ml.) B. m-Amlnophenol (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 380 400 2.00 NHo Extinction 1.60 0 NH» 1.20 “ p-Phenylenedlamine 0.80 A^ 0.40 0.00 220 IB \» 240 260 B A 280 300 320 340 360 380 400 Wave Length (millimicrons) B. p-Phenylenedlamlne Dlbydrochlorlde (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 2.00 NH 1.60 Extinction iNH 1.20 o-PhenylenedlHmlne 0.80 0.00 220 240 260 280 300 320 340 360 380 400 Wave Length (mllllmlcrone) Figure 8. A. o-Phenylenedlamlne (0.000045 g./ml. B. o-Phenylenediamlne (0.000045 g./ml. Sodium Sulfite (0.000090 g./ml.) 2.00 NH 1.60 Extinction NH 1.20 m-Phenylenediamlne < 0.80 0.40 0.00 220 260 260 300 360 Wave Length (millimicrons) Figure 9. A. m-Phenylenedlamlne (0.000045 g./ml.) B. m-Phenylenedlamlne (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 380 400 2.00 Extlnotlon 1.60 HNCH 1.20 Elon 0.80 0.00 220 260 280 300 320 360 380 *00 Wave Length (ollllmlcrone) Figure 10. A. Ilon (Monomethyl p-Amlnophenol Sulfate) (0.0000*5 g./ml.) B. Elon (Monomethyl p-Amlnophenol Sulfate) (0 .0000*5 g./ml.) Sodlun Sulfite (0.000090 g./ml.) 2.00 1.60 Extinction NH. NH2 Amidol 1.20 0.80 0.*0 0.00 220 240 260 280 300 320 380 360 *00 Wave Length (millimicrons) Figure- 11. A. Amidol (Dlamlnoohenol Dlhydroohlorlde) (0.0000*5 g./ml.) B. Amidol (Dlamlnoohenol Dlhydroohlorlde) (0.0000*5 g./ml.,)_ Sodium Sulfite (0.000090 g./ml.) 2.00 Extinction 1.60 l.PO h n c h 2c o o h — Olyoln 0.80 O.AO 0.00 220 260 280 300 320 360 380 Wave Length (millimicrons) Figure 12. A. Glycin (p-Hydroxyphenyl Glycin) (0.0000*6 g./ml) B. Olyoln (p-Hydroxyphenyl Glycin) (0.0000*6 g./ml.) Sodlun Sulfite (0.000090 g./ml.) *00 Extinction 1.60 1.20 Phenol 0.80 0.40 0.00 220 260 280 300 320 380 360 400 Wave Length (millimicrons) Figure 13. A. Phenol (0.000045 g./ml.) B. Phenol (0.000045 g./ml.) Sodium Sulfite (0.0.00090 g./ml.) 2.00 Extinction 1.60 1.20 Quinone 0.80 0.00 220 240 260 280 300 320 360 380 Wave Length (millimicrons) Figure 14. A. Quinone (0.000045 g./ml.) B. Quinone (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) Extlnotlon 1.60 CH? 1.20 p-Cresol 0.80 0.40 0.00 220 240 260 300 320 360 380 Wave Length (millimicrons) Figure 15. A. p-Cresol (0.000045 g./ml.) B. p-Cresol (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 400 0.25 OOCCH Extinction 0.20 — 0.15 OOCCH ^ --- Dlacetylhydroqulnone 0.10 0.05 0.00 220 240 260 280 300 360 320 580 Wave Length (mlllimicrone) Figure 16. A. Dlacetylhydroqulnone (0.000045 g./ml.) B. Dlacetylhydroqulnone (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 2.00 Extinction 1.60 OCHj p-Hethoxyphenol 1.20 0.80 0.40 0.00 260 220 280 360 300 380 Wave Length (mllllmlorona) Figure 17. A. p-Methoxyphenol (0.000045 g./ml.) B. p-Methoxyphenol (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 2.00 nh2 Extinction 1.6 0 s o 2n h 2 Sulfanilamide 1.20 0.80 0.40 0.00 220 240 260 280 300 320 340 360 Wave Length (mllllmlorone) Figure 18. A. Sulfanilamide (0.000009 g./ml.) B. Sulfanilamide (0.000009 g./ml.) Sodium Sulfite (0.000090 g./ml.) 380 400 2.00 NH 1.60 ,CH OH. CH CH. NH o 1.20 4* Dlamlnodurene g *3 & 0.80 0.00 220 240 260 280 300 320 360 380 400 Wave Length (mllllmlorons) Figure 19. A. Dlaolnodurene Dlhydroohlorlde (0.000045 g./ml.) B. Dlamlnodurene Dlhydroohlorlde (0.000045 g./ml.) Sodlun Sulfite (0.000090 g./ml.) 2 .0 0 1.60 o 1.20 oil ,01 Cl1 Cl Tetra- H chlorohydroqulnone *3 O c & 0.80 0.00 220 240 260 280 300 320 360 380 Wave Length (millimicrons) Figure 20. A. Tetraohlorohydroqulnone (0.000045 g./ml.) B. Tetraohlorohydroqulnone (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 2.00 1.60 CH iCH CH. OH o 1.20 *3 O Durohydroqulnone C 2 0.80 0.00 220 240 260 280 300 320 360 Wave Length (millimicrons) Figure 21. A. Durohydroqulnone (0.000020 g./ml.) B. Durohydroqulnone (0.000020 g./ml.) Sodium Sulfite (0.000090 g./ml.) 380 400 i 3.00 1.60 CH- CH Extlnotlon CH 1.30 Cunohydroqulnone 0.60 0.40 0.00 330 340 360 380 300 330 360 380 400 Wave Length (mllllmlorone) Figure 33. A. Cunohydroqulnone (0.000030 g./nl.) B. Cunohydroqulnone (0.000030 g./ml.) Sodltm Sulfite (O.OOOOUO g./ml.) 3.00 1.60 CHExtinction CH1.30 p-Xylohydroqulnone 0.80 0.40 0.00 360 380 300 330 360 380 Wave Length (mllllmlorone) Figure 33. A. p-Xylohydroqulnone (0.000045 g./ml.) B. p-Xylohydroqulnone (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 3.00 1.60 Extlnotlon HO 1.30 'OH Fhlorogluolnol 0.80 0.40 0,00 330 360 380 300 330 360 Wave Length (mllllmlorone) Figure 34. A. Phlorogluolnol (0.000045 g./ml.) B. Phlorogluolnol (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 380 400 2.00 Extlnotlon 1.60 1.20 Hydroquinone 0.80 0.40 0.00 220 260 280 300 320 340 360 Were Length (millimicrons) Figure 25. A. Hydroquinone (0.000045 g./ml.) Sodium Bleulflte (0.000090 g./ml.) B. Hydroquinone (0.000045 g./ml.) Sodlia Bleulflte (0.000090 g./ml.) Sodium Carbonate (0.0001 g./ml.) 2.00 Extlnotlon 1.60 1.20 Hydroquinone 0.80 0.00 220 260 280 300 320 360 380 400 Wave Length (mllllmlorone) Figure 26. A-Hydroquinone (0.000045 g./ml.) B-Hydroqulnone (o.000045 g./ml.) Potassium Sulfite Dihydrate (0.000090 g./ml.) 2.00 Extinction 1.60 1.20 0.80 0.00 220 240 260 280 300 320 3*0 360 380 Wave Length (mllllmlorone) Figure 27. A. Cysteine Monohydrochloride (0.000090 g./ml.) B. Cysteine Monohydroohlorlde (o.000090 g./ml.) Hydroquinone (0.000045 g./ml.) C. Cysteine Monohydroohlorlde (0.000090 g./ml.) Sodium Carbonate (0.0002 g./ml.)' Hydroquinone (0.000045 g./ml.) D. Hydroquinone (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) 2.00 Extlnotlon 1.60 1.20 Hydroquinone 0.80 0.40 0.00 220 240 260 280 300 320 360 380 Wave Length (millimicrons) Figure 28. A. Hydroquinone (0.000045 g./ml.) B. Hydroquinone (0.000045 g,/ml.) Sodium Sulfite (0.0000225 g./ml.) C. Hydroquinone (0.000045 g./ml.) Sodium Sulfite (0.000045 g./ml.) D. Hydroquinone (0.000045 g./ml.) Sodium Sulfite (0.000090 g./ml.) E. Hydroquinone (0.000045 g./ml.) Sodium Sulfite (0.000180 g./ml.) m 2.00 1.60 3'2--- 1.20 Tetramethylp-phenylenedlamlne 0.80 0.40 0.00 220 240 260 280 300 320 340 360 380 '400 Nave Length (millimicrons) Figure 29. A. Tetramethyl-p-Phenylenedlamlne Dlhydroohlorlde B. Tetraaethyl-p-Phenylenedlamlne Dlhydroohlorlde Sodium Sulfite (0.000090 g./ml.) C. Tetramethyl-p-Phenylenediamlne Dlhydroohlorlde D. Tetramethyl-p-Phenylenedlamlne Dlhydroohlorlde Sodium Sulfite (0.000360 g./ml.) (0.000045 g./ml.) (0.000045 g./ml.) (0.000180 g./ml.) (0.000180 g./ml.) DISCUSSION _ THE PROPERTIES OF SODIUM SULFITE Since Stenstrom and Reinhard1 in 1925 noted that sodium hydroxide decomposed hydroquinone before its ultra­ violet absorption spectrum In alkaline solution could be determined, few,, if any, further investigations of hydro­ quinone in alkaline water solutions have been conducted. It is indeed fortunate that sodium sulfite is so diverse in its action.that it.allows hydroquinone and related com­ pounds to exist in weakly alkaline solutions. Although sodium sulfite is only weakly alkaline, it can. raise the pH of an.aqueous hydroquinone from the acid to the alka­ line side. If this compound did not possess any addition­ al property, the hydroquinone would decompose rapidly since in.the pHKrange 7.2 to 8.2, James, Snell and Weissberger^ found that its autoxidation rate is very nearly proportional to the square of the hydroxyl ion concentra­ tion. However, sodium sulfite, the same sodium sulfite so commonly Included in photographic developers as the preservative, has the property of inhibiting the autoxi­ dation of hydroquinone and other dihydroxybenzenes, the aminophenols, phenylenediamines, and similar reducing agents. Since the breakdown;of these compounds is ac­ celerated by the presence of their oxidation products, -9- sodium sulfite is believed.to act in the reduction of the oxidation rate by the removal of the oxidation products which are catalyzing the reaction10. Thus, it is evident that because of its oxidative inhibiting property the presence of sodium sulfite allow® a study to be made of its effecti.- on' compounds that normally would decompose at corresponding pH values produced by a- stronger alkali, possessing no:- preservative effect. THE CHARACTER OF THE SODIUM SULFITE EFFECTT The effect of sodium sulfite upon the dihydroxyben­ zenes, the amlnophenols, and the phenylenedlamines is at once evident- from a study of Figures 1 through 9 or Table I. This agent causes a spectral shift to longer wave lengths of the ultraviolet absorption maximum of hydros quinone (Figure 1), of the p-aminophenol (Figure 4), and of the p-phenylenediamine dihydrochloride (Figure 7). The ortho and meta members of eachi of the three series show/nonspectral displacement of their absorption maxima. The extent of the shift to longer wave lengths for hydro­ quinone is 17 millimicrons; for p-aminophenol hydrochlor­ ide, 25 millimicrons; for p-phenylenediamine dihydrochlor­ ide, 20 millimicrons. In each ca.se there is an increase in:the intensity of the: light absorption. Although it is true that each of these three compounds is a well- -10- known.developing agent used in photographic developers, it does not follow that sodium sulfite causes a spectral shift with every developing agent. Both o-dihydroxyben- zene (Figure 2)}and o-aminophenol (Figure 5) exhibit developing activity*!, though less powerful than the corresponding para isomer. enediamine (Figure 8). This applies also to o-phenyl- It appears, therefore, that the effect of. sodium sulfite is not one that can be correla­ ted to developer activity but rather to the actual struc­ ture of the compound. THE EFFECT OF SULFITE ON SUBSTITUTED BENZENE DERIVATIVES The action of sodium sulfite on substituted p-disubstituted benzene derivatives is further Illustrated by Figures 10-12. Elon or Metol (Monomethyl-p-aminophenol sulfate), Amidol (diaminophenol dihydrochloride), and Glycin (p-hydroxyphenyl glycin) show, a shift to longer wave lengths in their ultraviolet absorption spectra upon the addition of sodium sulfite. Diaminophenol di­ hydrochloride shifts 25 milimicrons, Monomethyl-p-amino­ phenol sulfate and p-hydroxyphenyl glycin each shift 30 millimicrons. also. There is a hyperchromia shift in each, case Again, each of these three compounds possess photographic developing activity and represent some of the most useful developing agents of today. However, it should again be emphasized that the sulfite effect is -11- based on structural reasons rather than coincidental developing activity. Each of these last three compounds possess Increased structural ..complexity from the parent compound, p-aminophenol. Dlaminophenol differs from this parent, compound in that it has an additional amino group ortho toe the hydroxyl group.. Although the extent of the spectral shift is the same for both compounds, the increase in the extinction value of the absorption is greater for the di­ amino phenol than for. p-aminophenol upon the addition of sodium sulfite. Monomethyl-p-aminophenol sulfate has a methyl group substituted for an amino:hydrogen; p-hydroxyphenyl glycin has a carboxymethyl group in place of the am­ ino hydrogen. Since the unsubstituted p-aminophenol shows a bathochromic shift of 25 millimicrons and since each of the substituted p-aminophenols give a bathochromic dis­ placement of 30 millimicrons, itls evident that the methyl group and the carboxymethyl group when: substituted on the amino group in place of a. hydrogen give an. increased batho­ chromic effect of 5 millimicrons. A possible explanation of the above observed differ­ ence might.be contained in the availability of the elec­ trons in the resonance structures of the amino group; in. both cases. The amino group, possessing an unshared pair of electrons, is a group that releases electrons to the "benzene ring^2 . The methyl group, as shown by electrical measurements, possesses a dipole with the carbon nega­ Thus, the monomethylamino group would possess tive^. greater electron-releasing tendency than the amino group due to the repulsive action on the electron pair of the amino nitrogen by the negative carbon atom of the methyl group. The explanation of the effect of the group -NHGH2COOH would have to involve the study of the group -NHCH2COO" since the sodium sulfite-glycin solution is alkaline. The negative charge resulting from the ioniz­ ation, would greatly intensify the electron-releasing power of the nitrogen of the amino group. Apparently, the increased freedom or availability of electrons for resonance is a prerequisite for increased bathochromlc effects by the sodium sulfite. EFFECT OR SULFITE O W VARIED BENZENE DERIVATIVES Since many investigators have investigated the effect of alkali on phenol and reported a bathochromlc shift, a:, comparison with the effect of sodium sulfite on this com­ pound would be instructive (see Figure 13) • The ultravi­ olet absorption spectrum of phenol fails to show a spec­ tral shift in a solution of sodium sulfite of the same concentration that produces the shift in hydroquinone solutions. Evidently, the other para substituted hydroxyl group ia essential before a phenolic compound will be affected by sodium sulfite. As mentioned previously, the carbon atom in a methyl group Joined to a ring carbon atom is the negative end of a dipole and the loosely-held electrons of the carbom atom of the methyl group are attracted by the ring carbon atom. This loss of electrons to the ring is somewhat akin to the action of the nitrogen atom, of the amine group and the oxygen atom of the hydroxyl group, both of which can and do furnish unshared electrons to conjugate with, the ring carbon atom. Although the electron-releasing power of the amino and hydroxyl groups is greater than the methyl group, it would seem that a compound such as p-cresol would be somewhat the electronic equivalent of hydroquinone and should give the characteristic bathochromic shift of its absorption spectrum upon the addition of sodium sulfite. However, as shown in Figure 15» the addition of sodium sulfite to p-cresol fails to produce any spectral shift. Further substitutions were then studied in which a part of the original substituent was retained instead of being replaced or displaced in its entirety. Hydro­ quinone diacetate (Figure 16) has a hydroquinone nucleus in which each hydrogen atom of the hydroxyl groups has 14— been replaced with a. -COCH^ group. This group has the net': effect of making; electrons less available to the ring. Apparently, this action is of such magnitude in its effect that the unshared electrons of the hydroxyl oxygen are not.released to the rihg as freely as in hydroquinone. Addition of sodium sulfite falls to pro> duce a spectral:, shift in this substituted hydroquinone. The substitution-of a methyl group for the hydrogen of one. of the hydroxyl groups of hydroquinone should, from.what has been said before, increase the electronreleasing properties of the oxygen. This methoxy group still possesses electron*releasing powers as shown by the. fact that it is an ortho-para orienting substituent, as is hydroxyl, in benzene substitutions but itc. does not have the power of the hydroxyl group. The addition of sodium sulfite to an aqueous solution of p-methoxyphenol produces no bathochromlc effect on: the ultraviolet ab­ sorption spectrum. Para-phenylenediamine dihydrochloride undergoes a bathochromlc shift of 20 millimicrons ini its absorption spectrum when:placed in:a sodium sulfite solution. If one of the aminoogroups of this compound is combined to: form the -S02NH2 group, it:might be presumed that., since the -S02- part of this group is highly electron-attract- -15 ing that there will be little chance for the amino group to furnish its unpaired electrons to:; the ring. This presumption is supported by the fact that the -SO2NH2 group is meta-orientlng for substituents during substi­ tution on the benzene ring. This action requires an e- ffeet on.the ring which makes electrons less available. As seen from Figure 18, introduction;of the -SO2NH2 group in:, place of. one of the amino groups of p-phenylenediamine gives a compound which in: the presence of sodium: sulfite fails to give the 20 millimicrons bathochromlc shift of the p-phenylenediamine itself. THE POSSIBILITY OF COMPOUND.FORMATION AS THE SULFITE EFFECT Sodium sulfite does not react with.aqueous solutions of hydroquinone. However, It does react with an oxidation: product.of this compound, namely, quinone, to: give a colorless compound, hydroquinone monosulfonate10. As can be seen from Figure 14, the maximum of the curve repre­ senting the ultraviolet absorption of a quinone-sodium sulfite solution is at 3.10 millimicrons while the maximum for: the hydroquinone-sodium sulfite solution! occurs at 305 millimicrons. This similarity in absorption; spectra, caused some concern, lest the sulfite effect, be one of addition; to hydroquinone in: solution to' give a mono- or disulfonate of hydroquinone. Such a compound formation: would result in a shift of the absorption spectrum to long­ er wave lengths1^. However, to postulate the existence of hydroquinone mono- or disulfonate as the cause of the bathochromic spectral shift,of hydroquinone upon addition of sodium sulfite is a highly improbable explanation. First, hydro­ quinone monosulfonate is a very weak developing agent^5 while hydroquinone-sodium sulfite solutions are active in developing photographic materials. It seems highly unlike­ ly that an unused developer like the latter would contain a sufficient concentration of the sulfonates so as to affect the light absorption. Secondly, potentiometric titration.of 100 milliliters of sodium sulfite (0.000090 grams per milliliter) by hydroquinone (0.000045 grams per milliliter), and the reverse titration, gave no results indicative of compound formation. Although not conclusive, this evidence would tend to support the conclusion that hydroquinone mono- or disulfonate formation does not occur in sufficient concentration so as to be a factor in the light absorption.. Next, sodium sulfite could only form compounds through substitution on the benzene ring. The removal of the elementary oxidation products of developing agents is a process of compound formation between, the oxi­ dized form of the developing agent and sodium sulfite. Elon (Monomethyl-p-aminophenol sulfate), hydroquinone, p-aminophenol, p-phenylenediamine,,Amidol (diaminophenol dihydrochloride), Glycin (p-hydroxyphenyl glycin) as well as pyrocatechol and o-aminophenol form at. least monosulfonates when, their oxidation products are formed in: sulfite-containing solutions^* If the effect of sodium sulfite was one of-addition to?, the oxidation products of the various developing agents studied in this work with the result, that the compound formed now/ is able to absorb light of greater wave length than.before, then both pyrocatechol and o-aminophenol should give a bathochromic shift of some extent intheir ultraviolet absorp­ tion spectra. However, as we have already outlined, the absorption, spectra,of the or-disubstituted benzene deriva­ tives thati exhibit, developing activity are unaffected by the addition of sodium, sulfite, indicating that, possible sulfonate formation.has not: occurred too a great: degree. There are also two further reasons indicating, im­ probability of actual sulfite-organic compound combi­ nation: into a; formal compound. Sodium sulfite is a. re­ ducing agentl that: exhibits preservative action ini aq­ ueous solutions of photographic developers. Cysteine is a reducing agent; that:, exhibits preservative action in aqueous solutions of photographic developers.^ Both of these reducing agents act in the same manner, by the re­ moval of oxidation products through compound formation. Cysteine in the presence of qulnone will give hydroquinone cysteine. As evidenced from Figure 27 > cysteine mono­ hydrochloride in an aqueous solution, of hydroquinone does not.give the bathochromlc spectral displacements, that sod­ ium sulfite would have given had it. been present. Obviously, for compound formation as projected above toooccur, a ring position must: be free from substitution. Thus, sodium sulfite does note, exhibit its preservative action on durohydroquinone since there is no ring position free from substitution1^. It would exhibit little, if any, inhibiting action on such compounds as diaminodurene and tetrachlorohydroquinone. As can be seen from Figures 19-21, Sodium sulfite solutions of these compounds under­ go spectral shifts, apparently indicating no necessity of an unsubstituted ring position. Likewise, from Figure 29, it appears that complete methylation of both amino groups of p-phenylenediamine does not render the compound in­ active to the action of sodium sulfite. EFFECTTOF SULFITE ON POLYSUBSTITUTED BENZENE DERIVATIVES There is a change in the ultraviolet absorption spectrum of diaminodurene. dihydrochloride upon the addir.' tion of sodium sulfite, as shown.by Figure. 19. A new. maximum is formed at 295 millimicrons while the original -19 maximum at 270 millimicrons of the sulfiteiess solution of the compound is retained. Tetrachlorohydroguinone undergoes a bathochromlc shift from 305 to 328 millimi­ crons upon addition of sodium sulfite. There is a possi­ bility that the halogens may be split off in alkaline solution but it is doubted that: the pH was high enough for this action to occur. In both cases, however, there are apparently shifts to longer wave lengths with increased light absorption. Bht durohydroquinone, a compound very similar to-diaminodurene, undergaes a shift to shorter wave lengths with a large increase in the intensity of light.absorption (Figure 21). While the hypsochromlc shift.of durohydroquinone is of the extent of only 9 millimicrons, the hypsochromlc shift of p-xylohydroqulnone is 36 millimicrons. And yet the addition of another meth­ yl group to p-xylohydroquinone to give the compound cumo-hydroquinone (Figure 22) renders this compound almost in­ active to the action of the sodium sulfite, the magnitude of the bathochromlc shift being only 2 millimicrons. Phlbrogluclnol (Figure 24) is not so?highly substituted as the above discussed compounds but is a 1,3,5-trihydroxybenzene. Although this compound does not have two: hydroxyl groups para to each other and although it is not a developing agent: , its ultraviolet absorption spectrum is shifted by sodium sulfite to longer wave lengths to the extent of 10 millimicrons. The above stated facts do not lend themselves to clear interpretation. Both durohydroquinone and diamino*- durene have a durene nucleus, and thus the methyl group moments would cancel in pairs. Since the small size of the amino (and hydroxyl) group does not.give sterlc in­ hibition of resonance1^, the expected spectral shift would be.toolonger wav^ lengths as exhibited by p-phenylenediamine (and hydroquinone). Since the spectral activity is not as indicated it must, be assumed that other mechanises muBt be at work. It is possible that structural factors may inhibit or prohibit the action.of the sulfite.The low/ solubility of polysubstituted benzene derivatives as well as the question.of purity also tend to complicate the problem and add further questions as to?the exact nature of. the action of sodium sulfite on these complex molecules. POSSIBLE SUBSTITUTES FOF SODIUM SULFITE An extensive attempt!.was made to find a substitute for sodium sulfite that could produce a like action on the spectra of the various organic compounds studied. A logical starting point was to: use another sulfite saltother than sodium. Potassium sulfite does give a bathos- chromic shift in the ultraviolet: absorption spectrum of -21 hydroquinone, as would be expected (Figure 26). With hydroquinone, sodium bisulfite in a concentration equal to-that .of the sodium sulfite gives the usual spectrum that is associated with the hydroquinone alone. However, addition of sodium carbonate to the extent, of 0.0001 gram per milliliter to insure complete dissociation of the bi­ sulfite ion. gives the spectral absorption characteristic of. the sulfite ion on. hydroquinone (see Figure 25). Sodium arsenite, sodium hypophosphite, sodium phos­ phite, sodium nitrite, sodium selenite, sodium sulfate, Kodalk (sodium metaborate), and potassium metabisulflte, as well as selenlous and phosphorous acids, were all tried unsuccessfully. I n each case the organic compound was hydroquinone (0.000045 gram per milliliter) while the concentration of the inorganic compounds was 0.000090 gram per milliliter. It; was concluded that only sodium sulfite, or a: sulfite salt other than sodium, or a salt that can be converted in.solution into sulfite ions, pro­ duces the spectral shifts observed upon its addition to the organic compounds capable of this action. Apparently, similarity of structure, as in the sulfite and selenite ions, is not: a^ sufficients factor to-produce spectral ac­ tivity characteristic of the sulfite. DISSOCIATION AND THE SULFITE EFFECT! The effect of pH on the spectra of various compounds has "been thoroughly studied^*2*2. Increasing the alkalin­ ity of a solution results in the ionization of ring hydroxyl and amino groups at definite values of the pH*. The ionization of a hydroxyl) or amino group would give a spectral shift to longer wave lengths,, according to the rule of Doub and Vanderibelt^.. The loss of a proton toy either group would cause a negative charge on the group.. The nature of this charge would enhance the electronreleasing power of the group and thus the electrons of the nitrogen.would toe more readily available for resonance structures. The spectral effect accompanying such loosen­ ing of the electrons is a shift of the maximum of the ab­ sorption spectrum to longer wave lengths. Sodium sulfite does raise the pH of aqueous solutions of hydroquinone. A solution of hydroquinone (0.000045 gram per milliliter) has a pH of 6.7. Addition of sodium sulfite (0.000090 gram per milliliter) raises the pH to 9.1. This latter value is very close to 9.8. the value of the pKi of hydroquinone. The value of the pKi represents the pH value at which 50 per cent of the compound is dissociated. From these facts it is a possibility that sulfite may toe causing the partial dissociation of hydro­ quinone.. This in turn would give rise to a bathochromlc shift in .the ultraviolet absorption curve of hydroquinone. To test the validity of the above possibility requires raising the pH of a hydroquinone solution in the absence of sodium sulfite toothe value of the pH in the presence of the sulfite. However, hydroquinone will not. exist unchanged in aqueous solutions of that alkalinity. As mentioned previ­ ously, cysteine is a preservative agent superior too even, sodium sulfite. Addition of cysteine monohydrochloride too hydroquinone solutions does not affect the spectral absorp­ tion of the hydroquinone (Figure 27), but. due toe the hydro­ chloric acid that is released, the pH is lowered. Hydro­ quinone (0.000045 gram per. milliliter) im solution with cysteine monohydrochloride (0.000090 gram per milliliter) gives aa pH?:value of 3*30. To raise the pH sodium carbon­ ate (0.0002 gram per milliliter) is added to the solution of the above twooconstituents. to 9.86. The pH :is thereby raised Even at: this value which is equal to> the pK^ of hydroquinone, the absorption curve (curve C, Figure 27) has noti, shown the spectral shift shown at a pH pf 9.1 in the presence of sodium sulfite. The curve of the hydro- quinone-cysteine-sodium carbonate solution shows a re­ duction in lightt absorption as well: as a small (two: milli­ microns) bathochromlc shift. On the evidence discussed above it would seem that although some dissociation of the hydroxyl and amino groups may occur, this dissociation -24- is not the primary cause of the spectral shifts observed when benzene compounds containing these groups are placed in sulfite-containing solutions. The alkalinity of the solution seems to be a criti­ cal factor, however. The addition.of only 0.0000037 gram per milliliter of hydrochloric acid is sufficient to cause a hypsochromlc shift of a. hydroquinone-sulfite solution, absorption spectrum to the spectrum character­ istic of the hydroquinone alone. The effect of the hy­ drogen ions of the acid would tend to? suppress the ioni­ zation of the ring hydroxyl groups. Although this effect and the lowering of the pH to 6.6 are effects of the acid, the further action of the hydrogen ions to convert the sulfite ions to bisulfite ions is the probable reason for the necessity of alkaline solution. It has already been demonstrated that, sodium bisulfite is without, ef fee toon the absorption.spectrum of hydroquinone (Figure 25). THE EFFECT OF VARIATION IN THE CONCENTRATION OF SULFITE The effect of varying the concentration of sodium sulfite while maintaining a constant concentration of hydroquinone was studied (Figure 28). The concentration of hydroquinone was 0.000045 gram per milliliter. When sodium sulfite of a concentration of 0.0000225 gram per milliliter is added to?.the solution of hydroquinone, the absorption spectrum decreases in light, absorption and shifts 7 millimicrons to longer wave lengths. This curve is characteristic of curves obtained during the breakdown of hydroquinone into varied oxidation products. The sod­ ium sulfite is present in sufficient concentration to raise the pH from 6.7 to 7.1 but it: is not, present, in sufficient concentration to- exert.adequate preservative action, toe prevent.the increased oxidative rate caused by the higher alkalinity of the solution. A .concentration of 0.000045 gram per milliliter of* sodium sulfite gives a spectral absorption, maximum at.300 millimicrons; a concentration of 0.000090 gram per milliliter gives a maximum at 305 millimicrons and the highest, light, ab­ sorption. Increasing the concentration of the sulfite to.0.000180 gram per milliliter gives an absorption maxi­ mum at 300 millimicrons but.slightly decreased extinction values. Further increases of concentration of. sodium sulfite up to 0.000540 gram per milliliter did not change the wave length value of the absorption maximum but the extent of the light absorption decreased slightly with increasing sodium sulfite concentration. As can be seen from Figure 28, the curves for hydroquinone-sulfite so­ lutions have a similar form once that sodium sulfite has reached a concentration of 0.000045 gram per milliliter. A similar series of sulfite concentration variations was run with p-phenylenediamine dihydrochloride. The p- phenylenediamine dihydrochloride had a concentration of 0.000045 gram per milliliter in each case.. Sodium sul­ fite of at.concentration of 0.000009 gram per milliliter did not; affect the absorption spectrum of the p-phenyl­ enediamine dihydrochloride which, has a maximum aft 285 millimicrons. Concentrations of sodium sulfite of 0.09. 0.0009, and 0.000090 gram per milliliter showed in each, of the three cases a.spectral.shift, of 20 millimicrons to 305 millimicrons. In the case of this more stable compound variation in.the concentration, of the sodium sulfite had no effect once a. sulfite concentration had caused a. shift in:the ultraviolet- absorption spectrum of the p-phenylenediamine dihydrochloride. As shown.by the above case, the spectral shift; due to sodium sulfite does not: occur until a certain; concen­ tration value is reached, then the absorption: maximum characteristic of the organic compound shifts suddenly to a: maximum value of both light, absorption and extent of spectral displacement to longer wave lengths. With hydroquinone this value occurs when the sodium sulfite concentration is twice the concentration of the organic compound. Further increases of sodium sulfite concen- -27- tratlon fall to give any further bathochromlc shift. The sudden, shift ati. a definite sulfite concentration Is somewhat: similar in action ton ionization: at. a. definite alkalinity value, indicating that;, the specific action of sodium sulfite requires definite conditions before it, occurs• -28 SUMMARY A general rule regarding the sulfite effect can be formulated: The addition of sodium sulfite to aqueous solutions of disubstituted benzene derivatives, contain­ ing either hydroxyl or amino groups, will produce a bathochromlc shift in the ultraviolet absorption spectra of only those compounds that have their substituents oriented para to each other. Substitution of one amino hydrogen by a group en­ hancing electron transfer to the ring increases the ex­ tent of the bathochromlc shift in substituted aminophenols. The insulation of an amino group from the ring by an intervening group, an electron-attracting group, has the effect of making the absorption spectrum of the new compound impervious to the action of sodium sulfite. The replacement of one or both hydrogen atoms of the hydroxyl groups of hydroquinone by methyl or acetate groups renders the compounds formed inert to the action of sulfite. Complete methylation of both amino groups of pphenylenediamine apparently does not inactivate the com­ pound to sodium sulfite. Although sodium sulfite combines readily with the -29- oxidation products of p-disubstltuted benzene derivatives studied, compound formation has been shown not to be the explanation of the action of the sulfite. Sodium sulfite causes both bathochromlc and hypsochromic spectral shifts with polysubstituted benzene derivatives, structural and resonance factors probably determining the end result. A sulfite salt other than sodium, or a salt con­ vertible to sulfite ions in solution, are the only com­ pounds of the many tried that resulted in the action characteristic of. sodium sulfite itself. The alkalinity of the solution alone has been shown, to be unable to produce the spectral shift credited to action of the sulfite. The spectral shift due to sodium sulfite does not occur until a certain concentration of sulfite is pre­ sent, then the absorption spectrum maximum shifts to the maximum extent and thereafter the shift is not increased by increasing the concentration of the sulfite. The sulfite effect, occurring even when the ring or amino substituents are completely blocked with methyl groups, appears to be an action in which the sulfite, either alone or in conjunction with the solvent, acts upon the p-substituted substituents to effect increased electron release by the oxygen and nitrogen atoms. Such a loosening of the electronic structure would result in the absorption of light of greater wave length (and less energy) than would be possible if the sodium sulfite was not present. -31- BIBLIOGRAPHY (1) Stenstrom and Reinhard, J. Phys.. Chem. 2£, 1477 (1925). (2) Morton and Stubbs, J. Chem. Soc., 1347 (1940). (3) Lemon, J. Am. Chem. Soc. 6g, 2998 (1947). (4) Doub and Vandenbelt, J. Am. Chem. Soc. 62, 2714 (1947). (5) Klotz, Chem. Rev. 41, 373 (1941). (6) Merrill, Spencer and Getty, J. Am. Chem. Soc. 70, 2460 (1948). (7) Merrill and Spencer, J. Am. Chem. Soc. JO, 3683 (1948). (8) Cary and Beckman, J. Optical Soc. Am. J51, 682 (1941). (9) James, Snell and Weissberger, J. Am. Chem. Soc. 60, 2084 (1938). (10) James and Weissberger, J. Am. Chem. Soc. 61, 442 (1939). (11) Mees, The Theory of: the Photographic Process, Macmillan Company, New York, 1944, p. 341. (12) Gilman, Organic Chemistry, An Advanced Treatise, Wiley and Sons, New York, 1945» Second Edition, Volume II, p. 1975-78. (13) Remick, Electronic Interpretations of. Organic Chemistry, Wiley and Sons, New York, 1947# p. 90-95. (14) Brode, Chemical Spectroscopy, Wiley and Sons, New York, 1943» Second Edition, p. 210. (15) James and Higgins, Fundamentals of Photographic Theory, Wiley and Sons, New York, 1948, p. 98. (16) Mees, The Theory of the Photographic Process, Macmillan Company, New York, 1944, p. 382-390. (17) James and Weissberger, J. Am..Chem. Soc. 60, 98 (1938). (18) Neblette, Photography, Its Principles and Practice, Van Nostrand Co., New York, 1946, Fourth Edition, p.. 318. -32- i (19) Pauling, The Nature of the Chemical Bond, Cornell University Press, Ithaca, N. Y., Second Edition, 1945, p. 223. i -33-