RAPID REACTION OF SINGLET MOLECULAR-OXYGEN (O-1(2)) WITH P-AMINOBENZOIC ACID (PABA) IN AQUEOUS-SOLUTION

The reaction of singlet molecular oxygen (O-1(2)) with p-aminobenzoic acid (PABA) is quite rapid. The rate constant for reaction of O-1(2), with PABA was measured in buffered aqueous solution by the method of competition kinetics and found to be 8.9x10(8) M(-1) sec(-1). The results of a Stern-Volmer analysis indicate that additional loss of(1)O(2), does not occur through physical quenching by PABA. Although illuminated PABA solutions are known to form O-1(2), it appears that PABA is also a very efficient sink for O-1(2). (C) 1995 Academic Press, Inc.