Pulse radiolysis of adrenaline in acid aqueous solutions

Abstract

Pulse radiolysis of adrenaline in acid aqueous solutions (pH 1–3) was carried out. The rate constants for the reactions of adrenaline with H and OH were determined: k(H + adr.) = (0·9±0·1) × 10⁹ dm³ mol⁻¹ s⁻¹; k(OH + adr.) = (1·65±0·15) × 10¹⁰ dm³ mol⁻¹ s⁻¹. The H-adduct of adrenaline has two λ_max, at 280 and 355 nm, with ϵ₂₈₀ = 420 m² mol⁻¹ and ϵ₃₅₅ = 390 m² mol⁻¹, which disappears according to a first order reaction, k₁ = 1·4 × 10³ s⁻¹. The spectra formed by OH attack was assigned to the corresponding benzoxy radical with absorption maxima at 285 and 365 nm and ϵ₂₈₅ = 620 m² mol⁻¹ and ϵ₃₆₅ = 105 m² mol⁻¹. Due to the overlapping of the intermediates, no decay kinetics could be obtained.