Chlorosulphonation of 2,4-dimethylacetanilide

Abstract

The reaction of chlorosulphonic acid with 2,4-dimethylacetanilide was described in two patents the orientation of the sulphonyl group in the sulphonyl chloride formed (m.p.147º) was not stated. This reaction was later repeated and was said to yield 5-acetamido-2,4-dimethylbenzenesulphonyl chloride which had a lower melting point (133-134º). Because no rigorous proof of the constitution of the product was given by these authors, the reaction was reexamined and is reported here. The acetamidodimethylbenzenesulphonyl chloride obtained in this work had m.p. 146.5-147º. It reacted with ammonia to give 5-acetamido-2,4-dimethylbenzene-sulphonamide which was hydrolysed to 5-amino-2.4-dimethylbenzenesulphonamide. The constitution of these products was established by diazotizing the latter compound and converting it into 5-iodo-2,4-dimethylbenzenesulphonamide. The melting point of the iodo compound (188-188.5º) differed from the melting point (176º) described in the literature for this compound which was prepared by sulphonation of 1-iodo-2,4-dimethylbenzene followed by conversion into the sulphonyl chloride and then into the amide. 5-Iodo-2,4-dimethylbenzenesulphonamide was reduced with zinc and ammonia to 2,4-dimethylbenzenesulphonamide whose melting point was similar to the value in the 1iterature it did not depress the melting point of an authentic sample made in two steps from sodium 2,4-dimethylbenzenesulphonate, and its p.m.r. spectrum was consistent with its structure, i.e. H5 and H6 gave a quartet with a coupling of 9 Hz characteristic of ortho benzene protons.