Study of (CH3)2C(OH)CH2O2 using modulated photolysis: ultra-violet spectrum and self-reaction kinetics

Abstract

The ultraviolet absorption spectrum and the kinetics of the self-reaction have been studied for the β-hydroxy(methyl)propylperoxy radical. Experiments were carried out using the modulated photolysis technique over the temperature range 298–349 K and pressure range 50–200 Torr. At room temperature, the value of the observed rate constant (molecule⁻¹ cm³ s⁻¹) was found to be: k_obs = (4.40 ± 0.70) × 10⁻¹² and the Arrhenius expression: k_obs(T) = (4.10 ± 0.2) × 10⁻¹⁵exp(2086 ± 160/T) molecule⁻¹ cm³ s⁻¹

This effective constant, defined as –d[(CH₃)₂C(OH)CH₂O₂]/dt = 2k_obs[(CH₃)₂C(OH)CH₂O₂]² corresponds to the total consumption of (CH₃)₂C(OH)CH₂O₂ radical via the reactions: 2(CH₃)₂C(OH)CH₂O₂ → 2(CH₃)₂C(OH)CH₂O + O₂→ (CH₃)₂C(OH)CHO + (CH₃)₂C(OH)CH₂OH + O₂(CH₃)₂C(OH)CH₂O₂ + HO₂ → (CH₃)₂C(OH)CH₂O₂H + O₂From the ratio β = [HO₂]_ss/[RO₂]_ss, determined in this work, and the branching ratio α for the mutual reactions (Ia) and (Ib) of the β-hydroxy(methyl)propylperoxy radical – found in the literature – the parameters of reactions (Ia), (Ib) and (VI) are evaluated at different temperatures. Our results are discussed and compared to literature data.