INDUSTRIAL AND ENGINEERING CHEMISTRY
454
TABLE111.
a
Nagel, W., Angew. Chem., 46, 576 (1933). Nagel, W.,Wiss. Ver6,fent. Siemens-Konzern, 10, 108 (1931). Nagel, W.,and Kornchen, M., Ibid., 6, 235 (1923). Rackwitz, M., Arch. Pharm., 245,415 (1907). Richmond, G. F.,Philippine J . Sci., 5A, 177 (1910). Ruzicka, L.,and Hoskings, J. R., Ann., 469, 147 (1929). Schaeffer, B.B.,Ph.D. thesis, Polytechnic Inst. Brooklyn, June, 1936. Schaeffer, B. B.,and Gardner, W. H., IND. ENG.CHEM., 30, 333 (1938). Seidel, “Uber die Darstellung und die Eigenschaften der Abietsauren,” Mannheim, 1913. Tschirch, A., and Engel, A., Arch. Pharm., 246, 293 (1908). Tschirch, A., and Kahan, M., Ibid., 248,433 (1910). (25) Tschirch, A., and Koch, M., Ibid., 240, 202
SOLUBILITY O F FRACTIONS IN ORGANIC LIQUIDS5
Solvent Nitrobenzene Benzene Isopropyl alcohol Octyl alcohols Butyl 2-ethyl acetate Ethyl acetate %-Butylether Methyl ethyl ketone Carbon tetrachloride Chloroform Dioxane
KIB I I S S I S I S I €3 S
KID I I S S I S I I I S S
KIIB I I S S I S I S I I
s
VOL. 30, NO. 4
KIID I I S S I S I I I I S
I = completely insoluble; 8 = completely soluble.
(1902’1. \ - - - - I
(26) Tschirch, A.,and Stephan, Ibid., 234,552(1896). TABLE IV. CHEMICAL COMPOSITION AND MOLECULAR WEIGHTOF FRACTIONS(27) Importers’ Assoc* and Am* Shellac Mfrs.’ Assoc., Official Methods of Mol. Weight Analysis, Specifications and General InformaCalcd. Total No. tion on Shellac and Bleached Shellac, pp. 3G-7, from. COOH New York, 1934. SaponisaponiBy and Acid fication Ester fication Rast COO (28) Verman, L. C., and Bhattacharya, R., London Fraction No. No. No. No. method Groups %C %H Shellac Research Bur.. Tech. Paver 1 (1934). . . Shellac 70.8 231.8 161.8 964 983 4 67.25 9.72 (29) Ibid., 5 (1935). KIB 90.6 255.3 164.7 878 784.5 (30) Weinberger, H.,and Gardner, W. H., IND.ENQ. 126.9 342.4 215.6 654 683 KID CHEM.,Anal. Ed., 5,267 (1933). KIIB 103.6 286.3 182.7 579 565 3 64.76 9.21 147.4 147.2 0.0 380 .. ... (31) Whitmore, W.F.,Weinberger, H., and Gardner, KIID K III .. . 2 57.1 654 593.6 ... .. W. H., Ibid., 4, 48 (1932);Farhen-Ztg., 8,3456 KIV 70.0 217.8 li7:8 1500 1448 8 ... .. (1933).
I
2
E:!;:
i:::
*.
..
isolated from saponified lac. It would thus appear that most of the components of shellac are inter-esters (which includes Iactides) of the constituent polyhydroxy acids. The fact that a large portion of the resin is soluble in ethyl acetate would support this contention. Presumably shellac also contains a small percentage of free acids in fraction KIID, which may constitute the natural plasticizer previously noted (6) to be present. The resin itself is probably a solid solution. This would account for the difference in properties between lac and its components. The data presented show that the individual molecular species are small in comparison with some of the inter-esters which have been prepared synthetically (2), or with the average molecular weight which has been assumed for shellac (1, 15).
RECEIVED November 2, 1937. This paper is based upon part of the these submitted by Benjamin B. Schaeffer and by Harold Weinberger in partial fulfillment of the requirements for the degree of doctor of philosophy at the Polytechnic Institute of Brooklyn, Brooklyn, New York. Contribution 48 from the Shellac Research Bureau and 44 from the Department of Chemistry of the Polytechnic Institute of Brooklyn. This research wa8 sponsored by the United States Shellac Importers’ Association and the Indian Lac Cess Committee.
Acknowledgment
HAROLD WEINBERGER AND WM.HOWLETT GARDNER
The authors wish to express their gratitude to Mrs. D. Norris and to R. W. Aldis for the sample of kusmi-khair shellac used in this investigation, and their appreciation to R. W. Aldis, R. Bhattacharya, and H, K. Sen for their kindness in reviewing this article.
Literature Cited (1) Bhattacharya, R., J . SOC.Chem. Ind., 54, 82 (1935). (2) Carothers, W.H.,and Van Natta, F. J., J . Am. Chem. SOC.,
55, 4714 (1933). (3) Coffignier, C., BUZZ. soc. chim., 7,1049 (1911). (4) Fowler, G.J.. U. S. Patent 975,224(Nov. 19, 1908). (5j Gardner, W. H., Brit. Plastics, 6 , 514 (1935). (6) Gardner, W. H., Shellac Research Bur., Polytech. Inst. Brooklyn, R e m r t s . 1928-34. (7) Gardher, W. H.,Caldwell, B. P., Rurnett, H., and Weinberger, H., Ibid., Research Note 5 (1937). (8) Gardner, W. H., and Harris, H. J., IND. ENG.CHEM.,Anal. Ed., 6,400 (1934). (9) Harries, C., and Nagel, W., Ber., 55,3833 (1922). (10) Ibid., 56, 1048 (1923). (11) Harrmann, P., and Kroll, N., Arch. Pharm., 265, 214 (1927). (12) Madihassan, S.,M. Pidance’s Report on Lac Refining, Osmania Univ. Press, Hyderabad Deccan, India, 1930. (13) Murty, N. N.,Weinberger, H., with Gardner, W. H., Indian Lac Research Inst., Namkum, India, and Shellac Research Bur., Polyteoh. Inst. Brooklyn, Research Note, 1937.
Chemical Composition of Shellac
S
HELLAC has been shown to contain polyhydroxy acids (2, 8,4, 9), and it has been suggested that these might occur as lactides (4) or as other inter-esters‘ (11)in producing the resin. The picture of shellac as consisting only of a mixture of lactides was questioned by the authors when they studied the rates of saponification of shellac (11). A solid solution of chain inter-esters of dissimilar polyhydroxy acids might, however, account for its resinous character. Any method for separating the parent hydroxy acids is limited if it consists in first saponifying the mixture of these naturally occurring condensates (9). Many of the disturbing influences encountered in such procedures can be eliminated if the resin is first fractionated into simpler component mixtures before saponifying and attempting to separate the constituent acids. This paper describes a study of the chemical composition of the several materials obtained by the fractionation of shellac with organic liquids (10). I The terms “intra-ester” and “inter-ester” as used in this article are the same as those employed by W. H. Carothers [J. Am. Chem. Soc.. 51, 2550 (1929)l. An inter-ester denotes that type which would result from a condensation reaction with the loss of water between molecules; a n intra-ester results from the loss of water within z i molecule-e. g,. a lactone.
APRIL,1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
Analysis of the Fractions Each individual fractionwas saponified in alcoholic solution, and the constituent acids were separated by the
455
lization from diethyl ether. Fractional crystallization of the crude ester product showed that it was a pure compound and did not contain lower melting esters such as were found by Schaeffer and Gardner The acid Obtained method developed by Schaeffer and Gardner for this purpose from the methyl ester melted a t 99-100' C. Melting points (9). The method consisted of precipitating the insoluble of mixtures of the acid and of the ester with products prezinc salts, as two fractions, from an aqueous solution of the Pared by Schaeffer showed that they were identical. The potassium salts obtained from the saponification mixture, hydrazide was prepared The filtrate from this from the ester by heatsin0 precipitation was ing it with aqueous hythen placed in a refrigerdrazine hydrate. When ator a t 5' C. for 16 hours, crystallized from boilA study has been made of the composiand the small amount of i n g a l c o h o l it h a d a r e m a i n i n g zinc salts tion of the materials obtained by the fracm e l t i n g point of 139which separated were tionation of shellac with organic liquids. 140' C . and contained removed by filtration. Some of these fractions apparently con8.87 per cent nitrogen as This was repeated until determined by the Jamiesist of single components which are no further signs of preson method (6). Theory inter-esters of the parent acids found in cipitation took p 1a c e. for this compound reThe soluble zinc salts shellac. One of the fractions is composed quires 8.80 per cent niwere then separated into entirely of uncombined parent acids adtrogen. Schaeffer and two fractions by convertmixed with the yellow dye, and another Gardner obtained 8.78 ing them to sodium salts per cent and Nagel (6) fraction is a mixture of inter-esters and and adding lead acetate 8.79 per cent for their free acids. Four new acids were isolated to an alcoholic solution products. The melting of these salts. for the first time in this investigation. points of the acid and The shellac acids in These were lacolic lactone, kerrolic acid, a the two derivatives were this investigation were new isomer of aleuritic acid, and a liquid identical to those found then obtained by passby these two other inacid. ing hydrogen sulfide into vestigators but differed suspensions or solutions slightly from those found of t h e h e a v y m e t a l by Rittler (8), who had salts in 95 per cent probably isolated an isoalcohol. After remer of this acid (9). He moving the insoluble metal sulfide by filtration and washing obtained a melting point of 101 ' C. for the acid, 70-71 " C. for i t with warm alcohol, the solution was distilled under rethe methyl ester, and 136135' C. for the hydrazide. duced pressure to remove the dissolved gas and to conLACOLJC LACTONE.An amorphous white powder melting centrate it to a relatively small volume. Distilled water a t 90-91 ' C. was obtained from the alcohol solution in which was then added until the solution just became turbid. The the insoluble lead salts of the third fraction of shellac acids latter was then clarified with a drop of alcohol and placed had been suspended and treated with hydrogen sulfide. in a refrigerator to crystallize. This product was also soluble in methyl alcohol, n-butyl The shellac studied was the kusmi-khair sample dealcohol, tert-butyl alcohol, and ethyl acetate, and in warm scribed in the previous article. The same symbols are used dioxane and chlorbform. It was apparently insoluble in here for simplicity to designate the fractions given in Figure cold water but dissolved readily in the boiling liquid. A 2 of that article (page 451). It is impossible to describe mixture of amorphous and crystalline substances was obthese fractions adequately without continued reference to tained from this last solution. They melted from 98-138" C. the solvent scheme. but, when dried a t 100" C., were completely converted to the amorphous substance melting a t 90-91' C. Acid and Fraction KIIB saponification numbers showed the amorphous material to be a lactone, but no satisfactory elementary analyses could be This fraction was the largest obtained from solvent separaobtained which would give a clue as to its possible compotion of shellac and proved to be the simplest in composition sition. of those studied. There were no shellac acids having lead Careful fractional precipitation from ethyl acetate gave salts which were soluble in alcohol in this portion of the resin. three products of slightly different compositions and melting ALEURITICACID. The resin acids obtained from the points : small amount of colored zinc salts obtained as the first precipitate were semiliquid and red; a sodium carbonate r. M. p., 960 c . ; c, 62.55; H, 10.98 solution of these acids was a deep wine purple. This in11. M.p., 90-91" C.; C , 60.82; H, 10.23 111. M . p., 91-92°C.; C, 61.10; H, 9.94 dicated the presence of contaminating dyestuff. Esterification in methyl alcohol yielded a dark reddish brown viscous The values for the last two fractions agreed very well for a liquid from which were isolated crystals of methyl aleuritate compound having the formula CI4H2606where the calculated but no other crystalline material. values for carbon and hydrogen are 60.87 and 10.14 per cent, When the white zinc salts obtained as the second prerespectively. Nevertheless, examination under a microcipitate were treated with hydrogen sulfide, they yielded a scope showed that they were a mixture of amorphous yellow product melting a t 93-94' C. After twice recrystallizing and colorless crystalline substances. These could not be from dilute alcohol, aleuritic acid was obtained which melted separated. However, it had been observed during attempts a t 99.5--100" C. When the zinc salts were esterified in to purify the original amorphous material by adding zinc methyl alcohol, the white crystalline methyl ester was prochloride to a neutralized solution of the crude lactone that duced. This product melted a t 69-70' C. after recrystal-
-
456
INDUSTRIAL AND ENGINEERING CHEMISTRY
a small quantity of zinc salts precipitated when the mixture allowed to remain in a refrigerator for several hours. This would indicate that the crystalline contaminating material was aleuritic acid and that it might be removed in this manner. A fresh sample of this fraction of the shellac was saponified, and the salt fractions were reseparated. Special care was taken in this experiment to remove the last traces of insoluble zinc salts which precipitated a t 5' C. in accordance with the directions described above as a general procedure. The alcohol solution containing the acids from the lead salts was evaporated under reduced pressure to avoid any possible decomposition due to heating. When the bulk of the alcohol had been removed, the solution was light yellow and had the consistency of sirup. Distilled water was then added until the solution was slightly turbid. It was placed in a refrigerator at 5" C. for 16 hours. A viscous resinous mass separated. This was removed and dried in a vacuum desiccator over phosphorous pentoxide; a lemon-colored vitreous solid was produced which could be readily powdered. The powder was not hygroscopic. This product was purified by dissolving in ethyl alcohol and reprecipitating with water in the manner just described. The vitreous powder finally obtained melted a t 90-91" C. Fractional precipitation from ethyl acetate gave products of the same melting point as that dissolved, unlike the previous preparation. The product was uniform when examined under a microscope. Values from Rast molecular weight determinations and microcombustions agreed extremely well for a compound having the empirical formula ClaHz40a. Rapid titrations of weighed samples in alcohol with alcoholic potassium hydroxide gave a value equivalent to that for a monobasic acid, but the saponification number showed that the compound contained an ester such as a lactone group.
. was
Analysis. Calculated for C I ~ H ~ ~C,O64.84; ~: H, 8.11; molecular weight, 296; acid No. (monobasic), 189.2; saponification No. (lactone acid), 356.6. Found: C, 64.79, 65.00, 64.85; H, 8.50, 8.36, 8.54; molecular weight, 291, 298, 301; acid NO., 191; saponification No., 353.0.
The methyl ester was prepared by suspending the lead salt in absolute methyl alcohol and passing in dry hydrogen chloride gas. It was a yellow viscous liquid which was unchanged by drying in the vacuum desiccator. NO solid substances could be obtained from it by any of the various methods. The saponification number indicated that it was the monomethyl ester of the lactone. Analysis. Calculated for C17H2606:saponification No., 361.2. Calculated for ClsHsoOr: saponification No., 327.4; found: 353.0.
I n comparison, the lactone group was hydrolyzed (acetolysis) when the vitreous product was treated with acetic anhydride and the amorphous diacetyl ester isolated. Analyois. 282.7.
Calculated for C&tsoOs: ester No., 281.4; found:
None of the derivatives were crystalline. The hydrazide was a colorless viscous liquid, and the p-nitrobenzyl ester a viscous oil. p-Bromophenacyl bromide gave a semiliquid brown resin. All attempts to purify the possible dipotassium salt obtained from saponified solutions of the compound gave the monopotassium salt of the lactone, similar to what was experienced by Schaeffer and Gardner (9). I n like manner, attempts to isolate the dibasic acid from the lead salt by the method employed by Bhattacharya (1) yielded only the
VOL. 30. NO. 4
lactone. This was expected since 30 per cent was the highest amount of lead which could be obtained in a preparation of this salt. The lead salt of the dibasic acid would have 49.4per cent lead. Preparations of purified zinc salts contained 17.70 and 17.76 per cent zinc, when obtained by treating the lactone dissolved in boiling water with zinc carbonate, and by the double decomposition of the potassium salts with zinc chloride in aqueous solutions, respectively. The zinc salt of the dibasic acid would have 17.24 per cent zinc, but the basic zinc: salt of the lactone would also have the same formula. The properties of the pure lacolic lactone as they have been described are summarized as follows: Physical appearance Melting point O C: Elementary aAa1 ma, % Empirical formu% Molecular weight Acid No. Saponification No. Hydroxyl No. Soluble in: Insoluble in: Methyl ester Hydrazide p-Nitrobenzyl ester
Yellowish, vitreoua solid
90-91
C 6488. H 8 4 6 c ; ~ H ~C;,H~~(OH) ~ o ~ ~(COO)COOH
-
296 .
191 355 375.5
Methyl alcohol, ethyl alcohol, ethyl acetate. waim dioxane. warm chloroform Diethyl ether, water, amyl acetate, ligroin Yellow viscous liquid Colorless viscous liquid Viscous oil
The compound differs from any constituent previously described. Its empirical formula would indicate that it might be a next higher homolog of the lactone described by Bhattacharya (d), an isomer of this homolog, or the lactone of an isomer of the homolog of shellolic acid (4). This new compound has been called L'lacolic lactone," following the precedent set by Harries and Nagel. The advisability of naming it at this time might be debated, but it was felt that this might simplify future reference to it. The estimated yields of the individual constituents of the fraction (KIIB) from several analyses were: colored material and impurities, 4 per cent; aleuritic acid, 46; lacolic lactone,. 46; and losses, 4 per cent.
Fraction KIB This fraction of shellac was also insoluble in ether and. next largest in amount. It yielded the following acids: ALEURITIC ACID. The colored zinc salts, as in the case of the first fraction of shellac, gave dark red viscous esters from which was obtained methyl aleuritate as crystals melting at 70" C. The colorless zinc salts contained only aleuritic acid, which was shown by preparing the acid, the methyl ester, and the hydrazide, and by determining the melting points of mixtures of each of these preparations with those obtained from fraction KIIB. LACOLIC LACTONE.The lead salts which were insoluble in alcohol gave a lemon-colored vitreous lactone which was identical in composition and in melting point with t h e lacolic lactone described above. Mixtures of the two preparations showed no change in melting point. They were identical in the other properties studied. The soluble lead salts were treated with hydrogen sulfide, and a white precipitate was obtained when the alcohol solution was treated in the usual manner. This granular product was removed by filtration, washed, and purified with dilute alcohol. Further addition of water to the filtrate produced more of this powdery precipitate. The product melted a t 105-107" C. It was almost completely soluble in chloroform and ethyl acetate but practically insoluble in diethyl ether. Protracted extraction in a Soxhlet apparatus, however, gave a diethyl ether extract of a small amount of material melting a t 89-90' C., which was similar to an acid subsequently found in fraction KID. The undissolved
APRIL, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
material now melted sharply a t 132” C. It was a colorless, granular, crystalline powder. Analysis. Calculated for C1&sa06: C, 59.9; H, 10.07; molecular weight, 320; acid and saponification No. (monobasic), 175. Found: crude material: C, 62.44, 62.50; H, 10.03, 10.05; purified: C, 59.6; H, 10.3; molecular weight (Rast) 323.8, 319.8, 320.8; acid and saponification No., 175.2, 175.5.
This analysis showed that the compound was a monobasic acid containing no lactone or other ester groups. A weighed sample was esterified with acetyl chloride at room temperature, and the ester isolated. This product had an ester number of 500.4 compared with a calculated ester number of 500.0 for a tetraacetyl derivative of an acid of the above empirical formula. Esterification of the original lead salts in alcohol gave a viscous yellow ethyl ester, which was converted to the hydrazide. The latter was a colorless crystalline compound which melted a t 135-136’ C. Elementary analysis showed it to have the predicted composition: Analysis. Calculated for ClsHs*OsN2: C, 57.44; H, 10.25; N, 8.40; molecular weight, 334.3. Found: C, 57.84, 57.70; H, 10.40, 10.35. N (Jamieson method), 8.47, 8.40; molecular weight (Rast), 334.8, 334.8, 321.6.
This derivative had the same melting point, molecular weight, and composition as the hydrazide previously obtained by Schaeffer and Gardner (9) from the mixture of ethyl esters of the alcohol-soluble lead salts which they obtained from saponified TN. orange shellac. Mixtures of this derivative with their hydrazide showed no lowering in melting point. When attempts were made to prepare other derivatives of this acid, the substance was found to be very susceptible t o the effect of heat. Ethyl alcohol solutions of the acid turned yellow slightly below the boiling point, indicating either decomposition or polymerization. When such solutions were evaporated to dryness, a clear yellow resin was obtained. Soft brown residues were obtained with p-bromophenacyl bromide and p-phenyl phenacyl bromide. The reaction with wnaphthyl isocyanate also produced a small amount of a soft yellow resin. The bulk of the precipitate from this reaction, however, was naphthyl urea, even though special precaution had been taken to dry the acid carefully before using it. The name “kerrolic acid” was selected for this acid in accordance with the frequent practice of many authors in naming components found in resins from their botanical or entomological source-viz., the official entomological name of the shellac insect is Laccifer lacca Kerr. The properties of the acid are summarized as follows: Physical appearanae Melting point, O C. Elementary analysis, %, E m irical formula Acig and sa onification No. Hydroxyl Molecular weight Soluble in: Insoluble in: Hydrazide Polymer
&:
White granular powder 132 C 59.6. H 10 3 c;~H~~o;; C’~~H~OH),COOH 175.0 700.0 320 Ethyl aoetate, ethyl alcohol, chloroform Diethyl ether Colorless crystals melting a t 135-136O C. Yellow resin
The estimated yields of the indivi’dual constituents obtained from fraction KIIB were: coloring matter and impurities, 2 per cent; aleuritic acid, 33; lacolic lactone, 32; kerrolic acid, 31; and losses, 2 per cent.
Fraction KID This fraction was one of two diethyl-ether-soluble component mixtures. Four salt fractions were obtained in separating the constituents after saponification. It contained approximately 45 per cent of dye and associated
457
material, 15 per cent of aleuritic acid, 15 per cent of lacolic lactone, and 15 per cent of an acid having a lead salt which was soluble in alcohol. ISOMER OF ALEURITICACID. Colorless crystals of the last acid were obtained from the soluble lead salts in the usual manner and, when recrystallized from ether, melted a t 89-90” C. Analysis showed that the acid was an isomer of aleuritic acid, the second isomer to be obtained in small amounts from shellac in this laboratory (9). Analysis. Calculated for Cl6HsZO6: C, ’63.12; H 10.53; molecular weight, 304; acid No., 184.2. Found: d, 63.19, 63.24; H, 10.51, 10.61; molecular weight, 302; acid No., 185.4.
The number of hydroxyl groups were determined by preparing the triacetate ester and ascertaining its ester number. Analysis. 401.6.
Calculated for CzzHa~Os:ester No., 390.7; found:
The acid gave a viscous liquid ethyl ester which was converted to a soft semisolid colorless hydrazide. This was purified with boiling absolute alcohol. Analysis. Calculated for ClaHsrNsO*: N, 8.8; molecular weight, 318. Found: N (Jamieson method), 8.76; molecular weight (Rast), 320.
Fraction KIID This fraction of shellac had a viscous liquid consistency which made precise weighing of the material very difficult. It was the second of the two ether-soluble fractions and contained only uncombined constituent acids as shown by the absence of any ester number. It was possible to isolate from it 55 per cent of colored matter, 25 per cent of aleuritic acid, 10 per cent of lacolic lactone, and 1 per cent of a viscous yellowish liquid acid. The amount of the last acid was so small that only an analysis of its sodium salt could be made. Analysis. Calculated for CoHl,OrNa: C, 50.94; H, 8.10; Na, 10.84. Found: C, 51.13, 50.91; H, 8.00, 8.14; Na, 10.9.
Fractions KIII and KIV These two fractions, comprising 22 per cent of the shellac, exhibited the property of forming insoluble aggregates (IO) which could not be completely saponified. Considerable difficulty was encountered therefore in separating the acidic constituents. Fraction I11 appeared to be composed almost entirely of equal amounts of two groups of acids-the white zinc salt and the soluble lead salt fractions. Fraction IV appeared to be composed of a very complex mixture of acids. Detailed study of these fractions has been reserved for another investigation. The estimated yields of the different acids isolated from the various fractions are summarized in Table I.
TABLEI. SUMMARY OF ESTIMATED YIELDSOF ACIDS ISOLATED (IN PER CENT) Aleuritic acid, 21.9: From fraction K I I B From fraction KIB From fraction K I D From fraction K I I D Lacolic lactone 20.8: From fractioh K I I B From fraction KIB From fraction K I D From fraction K I I D Kerrolic acid from K I B Aleuritic acid isomer from KID Liquid acid from K I I D Total yield of acids
14.0 4.3 1.9 1.7 14.0 4.3 1.9 ~
0.6
4.3 1.9 0.3 49.2
Colored material, 10.5: From fraction K I I B From fraction K I B From fraction K I D From fraction K I I D Wax Dirt and cellulose Fraction K I I I and KIV Total Losses
1.2 0.3 5.7 3.3 7.3 3.0 22.2
92.2
7.8 100.0
INDUSTRIAL AND ENGINEERING CHEMISTRY
458
Possible Components of the Fractions A possible picture of the composition of shellac can be reconstructed from the information presented in this and the preceding paper. I n no manner does this picture correspond to the hypothetical structures postulated by previous authors (7) for shellac resin, where they have assumed that a single molecular formula would suffice. Fraction KIIB, the largest, consists mainly of two resin acids, aleuritic acid, Cl~H2~(OH)3COOH, and lacolic lactone, C14H22(OH) (COO)COOH, in practically equal proportions.2 ~
~~
TABLE 11. FRACTION KIIB Molecular weight Acid No. Saponification No. Ester No. Hydroxyl No. ElEmentary analysis:
u
H
Found 565 103.6 286.3 182.7 521 64.76 9.22
Calcd. for CazHsrOo 582 96.2 288.6 192.4 481.0 65.98 9.28
A set of chemical constants and a molecular weight can be calculated for this fraction if we assume that the acids form a single inter-ester of a definite basicity. Table I1 compares the constants calculated for the monobasic inter-ester CazHuOowith those which have been reported (IO) for this fraction. This compound might be formed by the condensation of one molecule of each of the acids with a loss of one molecule of water. The agreement may be considered to be very fair in view of the fact that fraction KIIB contains a t least 3 per cent of extraneous material which could have been removed only with the greatest difficulty. It might also be assumed that this inter-ester does not contain a lactone group from the behavior of the compound during titration of alcohol solutions with potassium hydroxide. The respective hydroxyl and carboxyl groups which split off water to form the lactone group in lacolic lactone are present in the condensed molecule as part of the interester linkages. The free hydroxyl group in lacolic lactone is undoubtedly in a different position in relation to the free carboxyl group of this constituent acid from that of the same two groups which formed the lactone linkage. TABLE111. FRACTION KIB Found Molecular weight: Saponification No. Rast Acid No. Saponification No. Ester No. Elementary analysis: C
H
878 785 90.6 255.3 164.7 65.74 9.29
calculated for a monobasic inter-ester lactone acid composed of equal molecular portions of the three acids is given in Table 111. The agreement is good except for the acid and ester numbers, and the value for molecular weight which was obtained by the Rast camphor method. The discrepancy in acid and ester numbers can readily be explained as due t o a partial saponification of the lactone group during the determination of these values. The low Rast molecular weight value may have been due to loss of water from the hydroxyl groups contained in the kerrolic acid portion of the condensate. It will be recalled that this acid tended to decompose when heated in solution. It is unlikely that this fraction contained lower molecular weight inter-esters of these acids since we might expect from the solvent scheme to find such compounds in other fractions such as KIIB. It is also probably more than a coincidence that this fraction contains three different acids in practically equal proportions. One of the acids was not found in any of the other fractions studied. The two ether-soluble fractions, K I D and KIID, are an interesting contrast to the two previous fractions. Both K I D and KIID definitely contain a mixture of components. Fraction K I D contained, in addition to 45 per cent of colored material, equal amounts of three acids. The saponification number was nearly two and a half times the acid number, so that these acids might readily be present as an inter-ester. A monobasic inter-ester would have the maximum theoretical ester number but would account for slightly more than half of the ester number found for this fraction. Apparently the colored material contained substances having ester linkages. The K I I D fraction had practically no ester number, so that it was without doubt a mixture of free acids and dye. The acids isolated, unlike the other fractions, were found in different proportions.
Acknowledgment The authors wish to express their appreciation of the helpful suggestions of P. E. Spoerri and W. F. Whitmore, and to thank H. K. Sen, R. W. Aldis, and R. Bhattacharya for their assistance in reviewing the manuscript. They also wish to thank A. Gunz and L. Koprowski for their cooperation in carrying out some of the microcombustions for the analyses given.
Literature Cited Calcd. for CtsHsrO~r 884
.... 63.3
253.2 189.9 65.15 9.50
The values for fraction KIB also indicate that it consists of a single inter-ester, but in this case a condensate of three different acids: aleuritic acid, Cl~H~~(OH)3COOH; lacolic lactone, C14Hzz(OH)(CO0)COOH; and kerrolic acid, C16H27(OH),COOH. This fraction of the shellac was very susceptible to saponification with dilute potassium hydroxide solutions. This would indicate that the lacolic lactone retains its intra-ester as one of the groups of the larger molecule. A comparison of the observed values with those Philip Kirk recently isolated two crystalline acids from the insoluble lead salts of both this fraction and KIB. These will be described in a forthcoming paper. However, for the purposes of this paper, the original findings of Weinberger can be taken without greatly changing the conclusions which will be drawn with regard to the general structure of these fractions. f
VOL. 30, NO. 4
Bhattacharya, R., Chemistry & Industry, 55, 309 (1936). Bhattaoharya, R.,J . Sac. Chem. Ind., 54,82 (1935). Gardner, W. H.,Shellac Research Bur., Polytech. Inst. Brooklyn, Reports, 1928-34. Harries, C., and Nagel, W., Ber., 55, 3833 (1922). Jamieson, G. S.,Am. J . Sci., 4,33 (1912). Nagel, W., Wiss. Verbfent. Siemens-Konzern, 10, 108 (1931). Nagel, W., and Baumann, E., Ibid., 11, 99 (1932). Rittler, W., Jahrb. Math. Naturwiss. FakultLit Gbttingen, 55, No. 88 (1923). Schaeffer, B. B., and Gardner, W. H., IND.ENG.CHEM.,30, 333 (1938). Schaeffer, B. B., Weinberger, H., and Gardner, W. H., Ibid., 30,451 (1938). Whitmore, W. F., Weinberger, H., and Gardner, W. H., IND. ENG.CHEM.,Anal. Ed., 4, 48 (1932); Farben-Ztg., 38, 456 (1933). RECEIVED September 23, 1937. Presented before the Division of Paint and Varnish Chemistry a t the 94th Meeting of the American Chemioal Society. Rochester, N. Y., September 6 t o 10, 1937. This paper is based upon part of the thesis submitted by Harold Weinberger in partial fulfillment of the requirements for the degree of doctor of philosophy a t the Polytechnic Institute of Brooklyn, June, 1937. Contribution No. 49 from the Shellao Research Bureau and 46 from the Department of Chemistry of the Polytechnic Institute of Brooklyn. This research was sponsored by the United States Shellac Importers’ Association and the Indian LSCCess Committee.
