Compounds of Thiol Acids with Aldehydes by Maxwell P. Schubert

It has been shown (1) that both methylglyoxal and phenylglyoxal combine with thiol acids. Two types of compound were described. The first is a simple addition compound composed of 1 molecule of glyoxal and 1 of thiol, while the second is a condensation product formed by eliminating a molecule of water between a molecule of glyoxal and 1 of thiol. The second type is given only by cysteine and by thiourea. So far it has been impossible to determine the structure of these compounds, as they appear to dissociate into their components quite readily. For example, on treatment of the phenylglyoxal compounds with phenylhydrazine the osazone of phenylglyoxal is formed. However, it has now been found that the interaction of thiols and carbonyl compounds is much more general than was at first suspected and compounds of both the types mentioned above have been prepared with simple aldehydes. It seems better, therefore, to begin the study of the behavior of these compounds with the simplest possible combinations of thiol and carbonyl. Although thioglycolic acid is the simplest thiol acid, it was to be expected that if addition of thiols to simple aldehydes occurs quite generally, thioglycolic acid anilide would give such compounds in crystalline form more readily. This turned out to be the case and addition compounds were easily obtained with formaldehyde, butyric aldehyde, and chloral. The only simple imaginable structure for these compounds is