PULSE-RADIOLYSIS STUDY OF REACTIONS OF TETRACYCLINE WITH RADIOLYTICALLY GENERATED REDUCING SPECIES

The transients involved in the reaction of tetracycline (TC) with redu cing radicals such as e(aq)-, (CH3)2 COH and CO2.- have been character ized by the pulse radiolysis technique. The semi-reduced species forme d (lambda(max) = 630 nm, epsilon = 3.4 x 10(3) dm3 mol-1 cm-1) has bee n found to be a strong reductant with reduction potential lying in the range -0.450 to -1.40 V vs NHE. TC reacts with e(aq)- at diffusion-co ntrolled rates and the rate constant, depending upon the ionic form of TC existing at a particular pH, varies from 1.2 x 10(10) to 2.8 x 10( 10) dm3 mol-1 s-1. Based on these results a plausible site of electron addition has been suggested. Reaction of H atoms with TC gives rise t o a transient which exhibits spectral and kinetic features different f rom that of semi-reduced species.