Sensitized photo-oxidations of dissolved alcohols in homogeneous and heterogeneous systems Part 1. Homogeneous photosensitization by uranyl ions

Abstract

A sensitive and selective high performance liquid chromatography technique has been developed for the quantitative analysis of small amounts of carbonyl products resulting from the initial photodehydrogenation of various alcohols on interaction with the photosensitizer (UO 2 2+) * aq at 0.05 M. The method has been applied to determine the initial quantum efficiencies Φ 0(R 1R 2CO) at initial alcohol concentrations in the range 2 × 10 −4−2 × 10 −2 M for ethanol, isopropanol, cyclopentanol and benzyl alcohol. The sensitivity of the Φ 0(R 1R 2CO) values to H/D and D 2O/H 2O isotropic changes is examined using normal and perdeuterated isopropanol in H 2O and D 2O. Consideration is given to the ability of an encounter-complex-based model to account for the linear double-reciprocal relationship between [R 1R 2CHOH] and Φ 0(R 1R 2CO) (accurately obeyed by the photodehydrogenation results) and also to the degree of consistency of this and other models with extensive new data on the quenching of (UO 2 2+)* by aliphatic, alicyclic and phenyl-substituted alcohols in aqueous and acetonitrile solutions.