PHOTOOXYGENATION OF MAGNESIUM meso‐TETRAPHENYLPORPHYRIN*

On unsensitized photooxygenation magnesium meso‐tetraphenylporphyrin underwent oxidative ring cleavage yielding a bilitriene derivative as the sole product. Kinetic studies by quenching technique using singlet‐oxygen quenchers, ß‐carotene and α‐tocopherol, and by substrate direct disappearance technique (Foote and Ching) indicated that only singlet‐oxygen process is involved in the photooxygenation, and that the rate of total consumption of singlet oxygen (kQ+kR) is 1.0 ± 0.4 times 108M‐1s‐1.