Cyclic mechanism in the trapping of carbonyl oxides with alcohols and carboxylic acids

The reaction of diphenylcarbonyl oxide with alcohols and carboxylic acids, which has been classified as a nucleophilic trapping, is shown to be in the reactivity order: AcOH ≫ MeOH > CF3CH2OH > EtOH ≫ t-BuOH. A laser-flash spectroscopy indicated that the reaction of carboxylic acids is very fast, that is, one-tenth of the diffusion rate. These results suggest that the hydroxyl compounds react as an acid and a nucleophile at the same time and the major reaction is via the seven- and five-membered cyclic mechanism for RCO2H and ROH, respectively.