spectroscopy are removed, the spectra can easily be interpreted by well-known correlation rules. The only irregularity noted is in methyl 11-(benzylsulfonyl)undecanoate, where two bands occur betneen 1120 and 1150 cm.-‘ instead of the usual single -SO2-- stretching band. Sulfone derivatives of fatty acids in the presence of unsubstituted acids or their sulfide or sulfoxide derivatives are best determined in dilute solution, utilizing the esters; for analytical work on various members of the sulfone series, the solid-state spectra of the acids are preferred. ACKNOWLEDGMENT
The authors thank 31. S. Sewman,
Ohio State University, for the sample of 11-(methy1thio)-undecanoicacid. LITERATURE CITED
(1) Barnard, D., Fabian, J. M., Koch, H. P., J . Chem. SOC.1949, 2442. (2) Bellamy, L. J., “Infrared Spectra of
Comdex Molecules.” Wilev, ” . Xew York; 1954. (3) Ferguson, E. E., J . Chem. Phys. 24,
1115 (1956). (4) Jones, R. N., McKay, A. F., Sinclair, R. G., J . Am. Chem. SOC.74, 2575 (1952). (5) Kirkland, J. J., ANAL.CHEM.27, 1537 (1955). (6) Koenig, N. H., Swern, D., J . Am. Chem. SOC.79,4235 (1957). (7) Meiklejohn, R. A., Meyer, R. J., Aronovic, S. M., Schuette, H. A.,
Meloche, V. W., ANAL.CHEV.29, 329 (1957).
(8) Primas, H., Gunthard, H . H., Hela. Chim. Acta 36, 1659, 1791 (1953). (9) Schreiber. K. C.. ANAL.CHEM.21. ‘ 1168 (1949). ‘ (10) Sheppard, N., Trans. Faraday SOC. 46, 429 (1950). (11) Shreve, 0. D., Heether, &I R., .
Knight, H. B., Swern, D., AXAL. CHEY.22, 1498 (1950). (12) Sinclair, R. G., RIcKay, A. F., Jones, R. N., J . Am. Chem. SOC. 74, 2570 (1952).
RECEIYEDfor review July 20, 1957. Accepted November 6, 1957. Paper I11 in the series “Organic Sulfur Derivatives.” Paper I1 is (6). Mention of trade names does not constitute endorsement by the Department of Agriculture over similar products not mentioned.
Determination of Equivalent Weight of Esters and Halides with Cation Exchange Resins WlLLlS H. BALDWIN and CECIL
E.
HlGGlNS
Oak Ridge National laboratory, Oak Ridge, Tenn. Salts are formed during the heating of ethanolamine with phosphorus or sulfur esters, and alkyl halides. The solutions are passed through cation exchange resins (in the hydrogen form) where the cation of the salt i s exchanged for hydrogen. The free acid in the effluent solution i s titrated directly with alkali.
C
exchange resins are useful for the estimation of the equivalent ITeight of salts (6). The resins retain effective exchange capacity even in nonaqueous media ( 2 ) . Therefore, they can be used to follow the progress of reactions which produce salts. When such a reaction proceeds to completion the equivalent weight of the starting inaterial can be determined-e.g., the saponification of carboxylate esters IT ith alkali leads to the formation of the salt of the carboxylate anion. n’iesenberger ( 7 ) used this fact to estimate the acetate from the saponification of esters and amides. The usual estimation of the equivalent weight of carboxylate esters requires the titration of the excess alkali. However, the reaction mixture caii he passed through a column of a strongly acidic resin in the hydrogen form, liberating the free acid in the column effluent. Thus the acid formed in the reaction can be titrated directly. I n the present investigation, methods 11 ere devised for determining equivalent weights of a number of typical phosphorus or sulfur esters and alkyl halides. Salts formed in a preliminary reaction were treated with cation exchangers. ATIOI~
446
ANALYTICAL CHEMISTRY
JThile the saponification of carboxylate ester proceeds satisfactorily with sodium hydroxide or sodium alkoxide, this reaction is much slower with the esters of phosphorus or sulfur. Advantage was taken of the well known alkylation properties of the esters of the inorganic acids (1 5 ) . The heating of phosphate and sulfonate esters with ethanolamine produced salts. The resulting salt solution readily exchanged its cation for hydrogen when passed through a bed of cation exchange resin in the hydrogen form. Under the conditions used, only one alkyl group was removed from the polyesters of phosphorus. The reaction for salt formation may be represented:
The equivalent weights were calculated using the equation: Equivalent weight = weight of sample (mg.) [alkali required in test (ml.) - alkali in blank (ml.)] X normality of alkali
~
where the blank was 0.04 ml. of 0.1N sodium hydroxide with ethanolamine; it was often four to five h i e s higher with caustic digestion. The ion exchange technique as used to follow the rate of dealkylation of esters for the synthesis of acids and for the study of reaction kinetics. The principle of this method can be extended t o include any salt solution for which a satisfactory solvent can be found. (R0)nPO R’NH2 There is reason to believe, also, that it can (RO)~P(O)O- ~ H ~ R R ~ be extended to the determination of the equivalent weight of organic Rauscher (3. 4) used ethanolamine coinpounds, which are converted to for the quantitative identification of the corresponding bases, on passing carboxylate esters. Carboxylate esters the compounds through anion exchange react with amines to form amides resins in the hydroxyl form. IThich are not affected by the ion exchange resin as it is used here. EXPERIMENTAL Alkyl halides reacted with ethanolamine in an alkylation t j p e of reaction Materials. The esters and halides were synthesized by well known proleading to a substituted ammonium cedures or were the best commercial salt. grades Fyhich were distilled or crystalRX R’KH2 -L [RR’KH2+]Xlized before use. Propanol was refluxed with sodium and distilled, only The halogen acid was liberated quant h e middle two thirds was used. titatively by the resin. The compound, REGTIOX~ I I X T G R EAS.. Ipproxiethyl chloroacetate, reacted with ethniately 30 mg. of sample was vieighed anolamine, and hydrochloric acid was into a round-bottomed boiling flask fitted with a ground-glass joint. Five liberated quantitatively by the resin milliliters of sodium proposide (made without interference from the cardaily by dissolving 0.12 gram of freshly boxylate.
+
+
+
cut sodium in 100 ml. of propanol) was added and the mixture was refluxed for 1 hour. B. Approximately 100 mg. of sample and 250 mg. of ethanolamine, in a 5-ml. round-bottomed flask fitted with a cold finger condenser, were heated: (1) under gentle reflux for 2 hours, (2) under gentle reflux for 1 hour, or (3) in a boiling water bath for 1 hour. C. Approximately 100 mg. of sample vias mixed with 5 ml. of 1M potassium hydroxide in propanol. The mixture was heated for 1 hour in a boiling water hath. D . Approximately 100 mg. of sample was refluxed for 1 hour with 5 ml. of 1-If potassium hydroxide in methanol. Acidification and Titration. The r t w t i o n mixture was cooled t o rooni temperature a n d transferred t o t h e cation exchange resin column with 25 nil. of 50 or 70y0 ethyl alcohol in 5 portions. T h e column was washed \ \ i t h a n additional 100-ml. volume of t h e same ethyl alcohol. T h e rinsings f r o m t h e column were titrated with 0.05 or 0.lN sodium hydroxide (carbonate free) on a Fisher Titrimeter. Blank determinations were made in t h e same manner b u t omitting t h e sample. Column. Nalcite H C R ( D o a e s 50, 30 t o 100 mesh., 8 % , " cross linking) was washed with li-ater b y decantaiion t o remove finely divided material, and transferred t o t h e column (1 em. in inside diameter) to fill a volume of 10 to 15 ml. The column was washed with 300 ml. of 1N hydrochloric acid and then with n-ater until the washings were free of acid. The exchange is rapid, so that pressure on top the column or vacuum a t the outlet can be used to speed the n-ashing. The resin mas regenerated after use by n-ashing with 300 ml. of 1-V
Table I.
Equivalent Weight of Esters and Halides
Compound Ethyl p-nitrobenzoate Methyl stearateb Ethyl p-anisate Triethyl phosphate Tri (2-ethyl hexyl) phosphate Dibutyl butylphosphonate Tributyl phosphate Methyl p-toluenesulfonate Propyl p-toluenesulfonate Butyl p-toluenesulfonate Tetramethvlene dibromide
Butyl bromide
Equivalent Weight Calcd.a Found 195 194 299 294, 294, 296 180 179 182 183, 182 436 431, 435, 436 250 252, 253 266 269, 270 186 187, 187, 88, 180 214 215, 215 228, 228 228 108 108 108, 109 108 110, 111 13i 139, 139 142, 143, 44, 145 127 127, 128 123 123, 124
Reaction A A A B1
B1
B1 BI B2 B2 B2 B2 B3 C D B3 C B3 B3
Benzyl chloride Ethyl chloroacetate From formnla. Stearic acid precipitated in column and had to be mashed out with hot 95% ethyl alcohol. hydrochloric acid, though the resin can be mashed with 30 ml. of acid, then with freshly boiled distilled water until the washings were free of acid. Before each determination the resin column was washed with 30 ml. of aqueous ethyl alcohol of the same composition as that to be used for transfer of the sample to the resin and elution of the liberated acid. The column was frequently used for three or four determinations before regeneration became necessary. LITERATURE CITED
(1) Billman, J. H., Radike, A, Mundy, B. W.,J . Am. Chein. SOC.64, 2977
(1942).
(2) Chance, F. S., Boyd, G. E., Garber, H. J., Ind. Enq. Chem. 4 5 , 1671 (1953). (3) Rauscher, W.H., Clark, W.H.,J. A m . Chein. SOC.70,438 (1948). (4) Rauscher, W. H., AlacPeek, D. I,., ANAL.CHEU.22, 923 (1950). ( 5 ) Thomas, D. G., Billman, J. H., Davis, C. E., J . Am. Chem. Soc. 6 8 , 895 (1946). ( 6 ) Tan Etten, C. H., Wiele, 11.B., ASAL. CHEM. 2 5 . 1109 119531. 17) Wesenbergdr, E.,' Jfikrochemie oer. Jfikrochim. Acta 30, 241 (1942). RECEIVED for reviex July 5, 1957. Accepted Sovember 7, 1957. Based upon work performed under contract No. MTT405-eng-26 for the Atomic Energy Commission a t Oak Ridge Kational Laboratory.
Microdetermination of Chromium with 1,5-Diphenylcarbohydrazide THOMAS L. ALLEN Deportment o f Chemistry, University o f California, Davis, Calif. Operational variables in this microdetermination have been investigated. Included are the effects of pH, redistillation of water, nature and concentration of organic solvent, concentration and quality of 1,5-diphenylcarbohydrazide, a g e of stock solutions of this reagent, order of mixing, temperature, ionic strength, and shelf life of solid reagent. Also studied were the suitability of sodium peroxide for chromium oxidation and the solubility of 1,5-diphenyIcarbohydrazide in water and dilute sulfuric acid. With fresh solutions of a good grade of 1 3 diphenylcarbohydrazide, the molar absorbancy index of the colored product
at the absorption maximum of 546 (4.17 i 0.04) X lo4, based on the concentration of chromium(V1). m p is
investigators (1, 3-6, 16-19, 21) have found t h a t micrograni aniounts of chromium may be quantitatively determined with 1,s-diphenylcarbohydrazidc (s-diphenylcarbazide) . This reagent and chromium(V1) react in acidic solution to form a magentacolored product. The absorption maximum is a t or near 540 nip. If a large excess of reagent is used, the absorbancy of the solution is proportional to t h e formal concentration of chroANT
niium(V1)-that is, Beer's law is obeyed. However, there is a rather wide discrepancy in the literature rcgarding the value of the molar absorbancy index, u . ? ~(11) (also knonn as the molar extinction coefficient), a t the absorption maximum. Previously reported values, arranged in chronological order, are s h o w in Table I. \There literature values are based on molarity of dichromate, they have been divided by 2 in order to provide a common basis. These results were obtained in solutions of differing pH, concentration and type of organic solvent, etc. As differences in procedure might account for the difVOL. 30, NO. 3, MARCH 1958
a
447
