Photochemistry of some deoxybenzoins in micellar solutions. Cage effects, isotope effects, and magnetic field effects

The photolyses of 1,2-diphenyl-2-methyl-1-propanone (1) and its D-, 13C-, and alkyl-substituted derivatives 2 to 5 in various micellar solutions have been investigated. It was found that the extent of cage disproprotionation to yield benzaldehydes 6 and α-methylstyrenes 7 is enhanced by a factor of about 10 compared to the photolyses in homogeneous organic solvents. The advantage of using micelles rather than homogeneous solutions to enhance the magnitude of magnetic isotope and magnetic field effects on cage disproportionation is demonstrated. The results are interpreted in terms of a mechanism involving the competition between hyperfine-induced intersystem crossing of a triplet radical pair (3RP) to form a singlet radical pair (1RP) and escape of 3RP from the micelle