First evidence for the production of OH radicals by carbonyl oxides in solution phase - A DFT investigation

Dimesitylketone O-oxide (1) rearranges in solution to yield the alcohol 2-m ethylhydroxy-pentamethylbenzophenone (5) and dimesitylketone (6). DFT-B3LYP /cc-pVTZ calculations reveal that H migration from an o-methyl group to the terminal O atom of the COO unit of 1 rather than the isomerization of 1 is energetically the most favorable process. Calculated activation enthalpies (gas phase: 12.8 kcal/mol; CH3CN solution: 12.4 kcal/mol) are in excellent agreement with measured activation enthalpies (CFCl3 solution: 13.2 +/- 0. 2 kcal/mol; CH3CN solution: 12.5 +/- 0.3 kcal/mol). The hydroperoxide forme d by H migration decomposes to a OH and a benzyl radical. Recombination in the solvent cage leads to alcohol 5 while diffusion of OH out of the solven t cage yields 6. O 2001 Elsevier Science B.V. All rights reserved.