Molecular rearrangements. Part VIII. The influence of nuclear substituents on the rearrangement of N-chloroacetanilides

Abstract

N-Chloroacetanilides (X·C₆H₄·NClAc, where X = Cl, Br, CO₂Et, or COPh) rearrange to the corresponding chloroacetanilides in 99% acetic acid, low concentrations of hydrochloric acid being used to promote the change.

By comparison with N-chloroacetanilide (X = H) substituents lower the rate of rearrangement. The orientation of the substituents, when X = CO₂Et or COPh, does not greatly influence the rate of change: if X = Cl or Br, the meta-isomers rearrange much faster than the ortho- or para-isomers.

It was observed, that with a low molecular ratio of hydrochloric acid to N-chloro-compound, the reaction proceeded at a steady rate for at least half the change. The rearrangement became first-order with respect to the N-chloro-compound when the proportion of hydrochloric acid was raised.

Rearrangement was also brought about by toluene-p-sulphonic acid in 99%(v/v) acetic acid. The change is slow compared with that caused by hydrochloric acid, and it also follows a steady rate in the initial stages.