SINGLET MOLECULAR-OXYGEN [O2(1)DELTA(G)] PRODUCTION AND QUENCHING BY HYDROXYBIPHENYLS

A mechanistic study on the aerobic photooxidation of hydroxybiphenyls was carried out. Members of this family of compounds are widely employ ed as fruit pesticides. Rate constants for the quenching of singlet mo lecular oxygen [O2(1DELTA(g))] determined by time-resolved phosphoresc ence detection are in die range of 10(4) to 10(8) M-1 s-1, depending o n the solvent polarity, pH, and substitution pattern of the quencher. Quantum yields for hydroxybiphenyls photooxidation (PHI(r)) indicate t hat these substrates are good candidates for an O2(1DELTA(g))-mediated degradation under natural environments. Furthermore, these compounds proved to be good self sensitizers on irradiation at 308 nm. Quantum y ields for the production of O2(1DELTA(g)) (PHI(DELTA)) in the order of 0.1 in toluene and between 0.03 and 0.06 (depending on the substituti on) in D2O were determined.