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.