Photolyses of benzyl methyl substituted-benzyl carbinyl hypochlorites produced the corresponding carbinyloxy radicals, which undergo fragmentations. Oxidations of 1-aryl-2,3-diphenylpropan-2-ols by cerie ammonium nitrate also proceeded through quite similar homolytic beta-scissions. The relative rates and Hammett p(+) values are independent of temperatures. The differential activation parameters indicate that the entropic factors are important for the reactions. The differential entropic term (Delta S double dagger(Y-H)) could be related to the difference in the extent of bond cleavages caused by the different sigma(+) values of the substituents, Y and H, in the polar transition state (TS). The selectivities (relative rates) remain constant or even increase with increasing temperature, indicating that the reactivities are controlled by entropy. The polar TS can be caused by the perpendicular effect to invite the dual substituent effects with breakdowns of the Leffler-Hammond postulate. The solvent effects on the reactions of the three oxygen radicals are compared. A new scheme is proposed for hydrogen abstractions by solvated tert-butoxy and cumyloxy radicals.