Oct. 5, 1953
NOTES
4859
Thus, whilst the available chemical evidence does the monosodium salt (R’CH(S03Na)COaH,method not definitely differentiate between structures I M) 24 esters of the general formula R’CH(S03Na)and 111, the light absorption suggests that cyclo- C02R, where R’ is C14H28 (palmitate series) or octatetraene oxide is cycloocta-2,5,7-triene-l,4- C1&33 (stearate series). In 22 cases R was a normal alkyl group of 1 to 18 carbon atoms. Two oxide (111). Acknowledgment.-The author is indebted to esters of secondary alcohols were included. Tables Dr. E. A. Braude for helpful discussion and criti- I and I1 give the melting points, methods of prepcism, and to the Department of Scientific and In- aration, and elemental analyses. The elemental analyses agreed with the theoretical dustrial Research for a grant. values, the maximum deviation in the value for ORGANIC CHEMISTRY DEPARTMENT percentage of carbon being 0.47 and the average IMPERIAL COLLEGE OF SCIENCE AND TECHNOLOGY deviation 0.21. LONDON, S.W. 7, ENGLAND The sodium salts of the a-sulfonated esters were white hygroscopic solids, readily soluble in water, Sodium Salts of Alkyl a-Sulfopalmitates and the solubility decreasing with increase in molecular Stearates1#2 weight. They were unexpectedly resistant to hyBY J. K. WEIL,R. G . BISTLINE,JR., AND A. J. STIRTON drolysis, especially in acid solutions, presumably because the sulfonate group retards hydrolysis a t the RECEIVED MAY28, 1953 ester linkage through steric hindrance. Since saSalts of sulfonated esters of the higher saturated ponification of the esters may be incomplete even fat acids have been shown to be surface active after a four-hour reflux period with excess alcoholic agentsP3v4 but their preparation in a state of purity potassium hydroxide, saponification equivalent valhas not been adequately described. The reaction ues are not useful indications of purity. of liquid sulfur trioxide with palmitic or stearic acid The melting points of the methyl esters were conresults in a-sulfonation,6and we have now prepared siderably higher than those of the next four homofrom the diacid (R’CH(S03H)C02H,method D) or logs. Beginning with the hexyl esters, the comTABLEI, ClrHz&H(S08Na)COIR Melting point, OC.
Method
C
180.9-182.8 95.2-96.7 63.3-65.1 59.7-60.6 60 .8-61.6 (177-179) 189-190 (187-189) 202-203 (191-193) 206-206.5 d. (157-158) 168-168.8 (188-189) 219-221 d. (195-196) 217-219 d. 113.5-114.2
D D M M M M D D D D D
54.41 55.95 56.74 57.94 58.46 59.63 61.10 62.22 63.69 66.26 66.60 58.13
D
Elemental analyses found, % H S
8.63 8.96 9.13 9.33 9.50 9.69 10.06 10.21 10.74 10.59 10.88 9.55
8.62 8.42 8.01 7.78 7.63 7.14 6.85 6.32 5.93 5.53 5.17 7.75
TABLE11, ClsH&H(SO,Na)CO2R Melting point, ‘C.
Method
C
179.8-180.0 97.4-99.2 72.3-73.6 66.5-67.6 64.855.6 (167-169) 186.2-187.4 (170-172) 193-195 d. (191-193) 215216 d. (194-196) 208-210 d. (193-194) 218-220 d. (209-210) 221-223 d.
M D M M M M D D D D D
75.8-77.2
D
56.85 57.58 58.48 59.64 60.02 61.20 62.68 63.53 64.74 67.10 67.58 59.11
(1) This paper was presented at the Fall Meeting of the American Chemical Society, Chicago, Ill., September 7-11, 1953. (2) The palmitate esters, for example, may also be named as 2sulfohexadecanoic acid, 1-alkyl ester, 2-sodium salt or alkyl 2-sulfohexadecanoate. 2-sodium salt. (3) F. Guenther, J. Conrad and K. Saftien, U. 9. Patent 2,043,476 (June 9, 1986). (4) A. J. Stirton, J. K.Wdl, Anna A Stawitzke and 5.James, J . Am. OiZ Chemists SOC.,39, 198 (1952). (8) J, K. W d , L. P. Witnsuu and A. J. Stirtan, Txxa JOURNAL, T6, 8516 (1968).
Elemental analysis found, ?& H S
9.15 9.35 9.64 10.01 9.97 9.61 10.09 10.34 10.72 10.90 11.03
9.72
8.04 7.93 7.52 7.28 7.15 7.07 6.85 6.24 5.85 5.23 5.07 7.57
Na
6.20 5.91 5.66 5.47 5.29 5.08 4.78 4.59 4.36 3.91 3.66 5.56
-
Na
5.70 5.55 5.26 5.30 5.01 4.89 4.53 4.24 4.17 3.76 3.66
5.22
Dounds became transDarent solids a t the temDerak r e s noted in paren&eses, before melting soAe 10 to 30’ higher, usually with decomposition. Esters of secondary alcohols had higher melting points than esters Of corresvonding DrimaW alc0hds.Definite relativelq low m&ing p2nts have seldom been reported for &ali m e a salts of organic acids. Of low potassium ethyl sulfoacetate and potassium ethyl
NOTES
4860
a-sulfopropionate, melt a t 183 and 2 1 4 O , respectively.6 The yields of the a-sulfonated esters ranged from 28 to 76%, the lower yields usually being due to the solubility of the esters in the alcoholic solutions from which they were purified by crystallization. The isolation of the diacid and the two methods of preparation are described in the Experimental part. Method D was generally preferred, and the diacid was its own.esterification catalyst. Method Pvl: was most successful in the esterification of primary alcohols of 3 to 6 carbon atoms, of boiling points 98 to 155'. Experimental a-Sulfopalmitic Acid.-Stabilized liquid sulfur trioxide (0.613 mole) was added dropwise to a stirred slurry of 0:418 mole of palmitic acid in 500 ml. of tetrachloroethylene in the course of an hour; the temperature rose from 20 t o 35". The mixture was stirred a t 60-65' for an hour, cooled overnight at 5', and filtered. The residue was washed with cold chloroform and dried a t room temperature under reduced pressure. The somewhat impure diacid, obtained in 82% yield (neut. equiv. 173.0) could be used directly in esterification. Further purification by five crystallizations from chloroform a t O', and drying for five hours a t 75' at less than 1mm. pressure gave a white, hygroscopic solid, m.p. 90.191.1'. Small amounts of water may lower the melting point from this value by as much as 20'. Potentiometric titration in 95% ethanol gave points of inflection at pH values of 4.5 and 8.8, as shown in Fig. 1. Anal. Calcd. for Cl~H320bS: S, 9.53; neut. equiv., 168.2. Found: S, 9.33; neut. equiv., 170.8.
Vol. 73
sodium acetate was added, with stirring, to give a clear solution, which was cooled to -25' and filtered. The residue was washed with cold methanol and dried in a vacuum oven, t o give the crude ester as a light-brown solid. The yield was 93%. Purification by decolorizing with carbon and crystallizing twice from ethanol a t -20' gave a white, hygroscopic solid. The yield was 35%. Sodium Dodecyl a-Sulfopalmitate. Method D.-A solution of 0.062 mole of the diacid and 0.108 mole of dodecanolI in 200 ml. of toluene was heated and stirred a t the reflux temperature for four hours, with the azeotropic removal of water. The solution was then neutralized with solid sodium carbonate, decolorized with carbon, filtered, cooled to -25" and filtered. The residue was a light cream-colored solid; the yield was 58%. Sodium Amyl cu-Sulfostearate. Method M.-A mixture containing 0.138 mole of the monosodium salt, 200 g. of pentanol-1 and 2 g. of concentrated sulfuric acid was heated and stirred for six hours a t the reflux temperature, with azeotropic removal of water. The resulting clear solution was neutralized with solid sodium carbonate, decolorized with carbon, and filtered. The crude ester crystallized from the filtrate a t -27', was recrystallized from 50% ethanol and dried in a vacuum oven, giving the purified ester as a white hygroscopic solid; the yield was 76%.
Acknowledgment.-Microanalyses for carbon, hydrogen and sulfur were performed by Frances C. Strolle and Mary Jane Bythrow. This assistance is acknowledged with thanks. EASTERN REGIONAL RESEARCH LABORATORY?
PHILADELPHIA 18, PENNSYLVANIA
(7) One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. s. Department of Agriculture. Article not copyrighted.
Ultraviolet Absorption Spectra of Some Pyridine Derivatives BY MICHAEL YAMIN AND RAYMOND M. Fuoss
RECEIVEDAPRIL11, 1953
In a recent paper,' a series of quaternary derivatives of 1,2-di-(7 -pyridyl)-ethane and -ethylene were described. The parent bases form mixed crystals and are therefore difficult to separate by
8ooo 6000
0 VOLUME
4
6 0.1008N NoOH/O.I711
2
Fig. 1.-Potentiometric
a
IO
G. DIACID,ML.
titration of a-sulfopalmitic acid in 95% ethanol.
Sodium Methyl a-SulfopaImitate. Method D.-A solution of the diacid (0.142mole) in 250 ml. of methanol was heated at the r d u x temperature for 14 hours, and 12.3 g. of (6)
R. Andre-h,
Momulah., 48, 889 (1926).
I e '.
, 240
260
\
- - - - -- -.........,.. - - -- -
-*.k&: -I -.V-.-.r.rrV
280
.a.,
300
\I
320
mlr. Fig. 1.-Absorption spectra of 1,2-di-(y-pyridy1)-ethylene (solid curve) ; 1,2-di-(y-pyridy1)-ethane (dashed curve) and picoline (dotted curve) in 95% ethanol. (1) E. D. Bergmann, F. E. Crane, Jr., and R. M. Jonnn.~.T4.6879 (1962).
FUOES,
TBI.
