The production of the superoxide radical anion by the OH radical-induced oxidation of trimethylamine in oxygenated aqueous solution. The kinetics of the hydrolysis of (hydroxymethyl)dimethylamine

Abstract

The radiolysis of trimethylamine in N₂O/O₂ (4:1 v/v) saturated basic solutions eventually gives rise to dimethylamine, formaldehyde, and hydrogen peroxide. Pulse radiolysis using conductivity and optical detection permits the observation of the chemical transformations following the generation of the (dimethylamino)methyl radical from trimethylamine upon attack by the hydroxyl radical. The (dimethylamino)methyl radical reacts rapidly with oxygen (k = 3.5×10⁹ M^-1 s^-1) to give O₂^-1 and dimethylimonium, possibly via a short-lived (t_½^-6s) peroxyl radical. The dimethylimonium ion adds OH^- to form (hydroxymethyl)dimethylamine (k=2.8×10₈ M^-1 s^-1). This is hydrolyzed to dimethylamine and formaldehyde hydrate (k_obs=4.0 ± 0.6 s^-). A mechanism incorporating these reactions is shown to be in good accordance with the experimental data in the pH range from 9 to 11.3.