Pulse radiolysis of adrenaline in acid aqueous solutions

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.