Influence in kinetic studies by competitive photocurrent methods of a post-competition link between parallel reactions chains: Part II. OH radical addition to phenol and aniline

The rate constants for the homogeneous reaction of OH radicals of O^? ions with phenol and aniline have been determined by a photoelectrochemical method involving studies of the suppressive effect of mixtures of aniline and of phenol with methanol on the nitrous oxide photocurrent at a DME. Fairly good agreement with absolute rate constants obtained by conventional radiation chemical methods is obtained if use is made of the theory developed in Part I of this paper which takes account of the possibility of interaction between the photocurrent reaction chains following competition between the two organic solutes for OH radicals. The present work points to a value of 1.75±0.6 10¹⁰M^?1 s^?1 for the capture of OH by phenol at pH 9.5. The reaction product, the cyclohexadienyl radical Φ (OH)₂, is able to extract H atoms from methanol with a rate constant of the order of 10⁷M^?1 s^?1, this reaction tending to lessen the suppressive effect of a phenol + methanol mixture on the nitrous oxide photocurrent. Similar complications are observed at higher pH, and also when using aniline + methanol mixtures.