Reactions of aliphatic free radicals with copper cations in aqueous solutions. Part 3.—Reactions with cuprous ions: a pulse radiolysis study

Abstract

Helium-saturated solutions containing copper sulphate and an aliphatic alcohol (methanol, ethanol or propan-2-ol) were pulse irradiated. The kinetics of the reactions thus initiated were followed by the spectrophotometric and conductometric techniques. The results indicate that all three radicals, ·CR₁R₂OH, react with Cu²⁺_aq to yield Cu⁺_aq+ CR₁ R₂O + H₃O⁺. ·CH₂OH radicals react with Cu⁺_aq according to Cu⁺_aq+·CH₂OH ⇄ Cu^II—CH₂OH⁺, K≈ 5 × 10³ dm³ mol^–1. The corresponding equilibrium constants for Cu^II—CH(CH₃)OH⁺ and Cu^II—C(CH₃)₂OH⁺ are too low to be measured and the corresponding intermediates are not observed. Cu⁺_aq reacts with the β radicals, ·CH₂CH₂OH and ·CH₂CH(CH₃)OH, according to Cu⁺_aq+·CH₂CR₁R₂OH → Cu^II—CH₂CR₁R₂OH⁺. The latter intermediates decompose via acid catalysed reactions to yield Cu²⁺_aq+ H₂CCR₁R₂+ H₂O.