Laser flash photolysis of aqueous acetaminophen solutions

The N -acetyl-4-aminophenoxyl radical, a supposed intermediate of the enzymatic oxidation of acetaminophen in living organisms, was prepared and studied by means of nanosecond laser flash photolysis. A number of important spectral-kinetic parameters of this species were determined, namely, the absorption coefficient at 440 nm ((4.2±0.2)×10 3 l mol −1 cm −1 ), the quantum yield of acetaminophen photoionization at 266 nm (φ= 0.03), and the rate constants for recombination (2 k = (2.4±0.3))×10 9 l mol −1 s −1 ) and the reaction with the superoxide radical ( k = (9±2))×10 9 l mol −1 s −1 ).