Consideration on the effect of ortho-substituents of phenols by semiempirical molecular orbital method MOPAC

A MOPAC calculation is performed to explain the new ortho-substitutent effe ct of phenols proposed by the authors; an alpha-hydrogen of an ortho-substi tuent being used to regenerate a phenol from the phenoxy radical. The benzy l radical derived from the intramolecular hydrogen transfer of a phenoxy ra dical is found to be as stable as, or more stable than, the phenoxy radical . The regenerated phenol also is strikingly more stable than a quinoid type compound formed by the reaction of a phenoxy radical with another peroxy r adical. Thus, the new ortho-substituent effect mentioned above can also be well explained by this work. (C) 2000 Elsevier Science Ltd. All rights rese rved.