Kinetic demonstration of the intramolecular nature of the rearrangement of aromatic N-nitroso-amines (Fischer-Hepp)

✍ Scribed by D. L. H. Williams

• Publisher: John Wiley and Sons
• Year: 1975
• Tongue: English
• Weight: 370 KB
• Volume: 7
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550070206

✦ Synopsis

Abstract

Rate equations have been deduced for two possible mechanisms for the reactions of N‐methyl‐N‐nitrosoaniline in acid solution, namely, (1) for the generally accepted intermolecular mechanism which involves denitrosation followed by C‐nitrosation and (2) a mechanism involving intramolecular rearrangement which takes place concurrently with denitrosation. The observed rate constants obtained under various experimental conditions are consistent only with mechanism (2). In particular the question of halide ion catalysis differentiates clearly between the two mechanisms. Mechanism (1) predicts a first‐order dependence upon chloride (or other halide) ion under all conditions, whereas (2) allows a first‐order chloride ion dependence only in the presence of a large excess of a “nitrite trap” such as sulphamic acid, urea, hydrazoic acid, hydroxylamine, etc., whereas at the other limit of high concentration of added N‐methylaniline, the rate constants should be independent of the halide ion concentration. The predictions based on mechanism (2) are all borne out by experiment.