Reactions of N-Aryl-4-chlorobenzamides in sulphuric acid

Abstract

Rate constants of reaction of 4-chloro-N-phenylbenzamide at 353 and 373 K, and of N-benzyl-4-chlorobenzamide at 373 K have been studied in aqueous sulphuric acid. The rate acidity profiles in <40% w/w H₂SO₄ show the typical bell shape normally observed for the A2 hydrolysis of amides. However, with increasing acidity there is competition from sulphonation on the N-aryl substituent and subsequent A 2 hydrolysis of the sulphonated intermediates. At >75% w/w H₂SO₄, sulphonated 4-chloro- N-phenylbenzamide is charred. At >52% w/w H₂SO₄, sulphonation of N- benzyl-4-chlorobenzamide ceases and is replaced by A 1 hydrolysis of the substrate.