Reaction between bromophenol blue and aromatic nitrogen bases in chlorobenzene studied with a laser temperature-jump apparatus. Part 2

Abstract

The kinetics and equilibria of the reactions between bromophenol blue and five aromatic amine bases have been investigated with a laser temperature-jump apparatus. The reaction mechanism consists of two steps, a fast pre-equilibrium, followed by a slow intramolecular conversion of the hydrogen-bonded intermediate to the final product, an ion-pair complex. This slow step involves the motion of a proton along a hydrogen bond, which, despite the possibility of tunnelling, appears to be slow because the ordering of the solvent around the dipolar transition state causes the reaction to be unfavourable as regards both energy and entropy terms.,