Pulse Radiolysis of 3,4-Dihydroxytoluene

Abstract

Pulse radiolysis experiments of 3,4-dihydroxytoluene (DHT) were performed in aqueous solutions over a wide pH range (2–12). The rate constants for the reaction of DHT with the primary products of water radiolysis were determined: k(e–aq+ DHT)=(2 ± 0.2)× 107 dm3 mol–1 s–1 at pH = 7 and (1 ± 0.1)× 107 dm3 mol–1 s–1 at pH = 12; k(H + DHT)=(1.5 ± 0.2)× 109 dm3 mol–1 s–1 at pH = 2; k(OH + DHT)=(1.6 ± 0.1)× 1010 dm3 mol–1 s–1(pH = 2–7). The absorption spectrum of the H-adduct possesses two maxima (ε280= 290 m2 mol–1 and ε350= 300 m2 mol–1) and disappears according to a second order reaction (k2= 1.8 × 108 dm3 mol–1 s–1). By reaction of OH with DHT, an OH-adduct is formed, which is subsequently converted into the corresponding semiquinone radical by splitting water (k1= 3.7 × 104 s–1 at pH = 6.5). The species produced by reaction of DHT with electrons has also two absorption maxima (ε280= 300 m2 mol–1 and ε350= 120 m2 mol–1). A second order decay (k2= 9 × 108 dm3 mol–1 s–1) was established. Probable reaction mechanisms are suggested.