Hydrolytic Reactions of Esters and

The hydrolytic reactions of esters and amides of thiosulphurous acid ate investigated in a homogeneous medium. The esters are hydrolysed by alkali to gire sulphide, sulphite and thiosulphate whereas the amides are resistant towards alkali. Both the esters and amides are hydrolysed by acids giving hydrogen sulphide, sulphur dioxide, polythionates and elemental sulphur. The hydrolysis of these esters and amides in presente of sulphurous acid and thiosulphuric acid gives tetrathionate and hexathionate, respectively. THE formation of thiosulphurous acid has been postulated by the present authcrs during the alkaline hydrolysis of elemental sulphur in a homogeneous medium.' Further experimental support of the formalion of thiosulphurous acid as a primary product has been obtained by studying the hydrolytic reactions, in homogeneous medium, of dimethyl thiosulphite, diethy! thiosulphite, tetraethyldithiodiamine and dithiopiperidine. The quantitative analytical results of the hydrolytic reactions of these compounds in alkaline and acid media as well as in the presente of sulphurous and thiosulphurie acids are described in the present communication. EXPERIMENTAL Reagents Dimethyl and diethyl thiosulphites were prepared by reaeting sodium methoxide and ethoxide, respeetively, with disulphur diehloride. ~ These esters were purified by redistillation under redueed pressure. The boiling points and pereentage purities (as determined by the total sulphur estimation by the Carius method) were as follows: Dimethyl thiosulphite, boiling point 39~ purity 99.21~. Diethyl thiosull;hite, boiling point 64 ~ C./16mm., purity 98.91~. 130 Hydrolytic Reactions of Esters and Amides of Thiosulphurous Acid 131 Tetraethyldithiodiamine and dithiopiperidine were prepared by the method of Michaelis and Luxembourg 3 employing the reaction between diethylamine and piperidine, respectively, with disulphur dichloride. The former was purified by redistillation under reduced pressure and the latter by recrystallisation from alcohol. Tetraethyl dithiodiamine, boiling point l l0~ purity 99.38~: Dithiopiperidine, melting point 64~ purity 99.65%. These esters and amides were insoluble in water but soluble in benzene and carbon tetrachloride. Aldehyde-free ethyl alcohol and pure dry benzene were prepared by standard methods. 4 Sulphur-free carbon tetrachloride (Merck, extra pure) was d¡ and distiUed over phosphorus pentoxide. Other chemicals used were of the AnalaR grade. General Procedure The hydrolytic reactions were carried out in a homogeneous medium as in the earlier studies. 1, lo Five ml. of benzene or carbon tetrachloride were taken in a dry stoppered conical flask a n d a weighed amount of the ester or the amide wa~ introduced and dissolved. Forty-five mi. of an aqueous solution of carbonate-free sodium hydroxide (or hydroehloric acid, sulphurous acid or thiosulphuric acid) were then added and the immiscible liquids were homogenized by the addition of 75 mi. of alcohol and the contents were thoroughly shaken. The products of reaction were then analysed quantitatively by the analytical procedures of Kurtenacker and co-workers 5 for a mixture of sulphide, sulphite, thiosulphate and polythionates, and of Goehring and co-workers 6 for a mixture of polythionates. The total sulphur in solution was determined as barium sulphate after oxidation with bromine and nitric acid. The analytical results of alkaline and acid hydrolyses are presented in Tables I and II respectively. Tables III and IV present the analytical results of the hydrolytic reactions in presence of sulphurous and thiosulphuric acids, respectively. RESULTS Alkaline Hydrolysis The products of hydrolysis of the esters by alkali in homogeneous medium were found to be sulphide, sulphite and thiosulphate. The hydrolysis was incomplete in 89 hour at room temperature (25 ~ C.) although 94~ of the total sulphur could be accounted for in terms of the products. The 3.2 132 C.G. RAMACHANDRAN NAIR AND A. R. VASUDEVA MURTHY