Reactivity of 3-hydroxy-3-methyl-2-butanone: Photolysis and reaction kinetics

25 26 Hydroxycarbonyl compounds are important secondary reaction products in the 27 oxidation of Volatile Organic Compounds (VOCs) in the atmosphere. The 28 atmospheric fate of these oxygenated VOCs is however poorly understood, 29 especially the relevance of the photolytic pathway. In this work, a combined 30 investigation of the photolysis and temperature-dependent OH radical reaction of 331 hydroxy-3-methyl-2-butanone (3H3M2B) is presented. A photolysis lifetime of about 32 4-5 days was estimated with a global quantum yield of 0.10. The OH reaction rate 33 coefficient follows the Arrhenius trend (298 – 356 K) and could be modelled through 34 the following expression: k3H3M2B(T) = (5.12±0.07)×10 -12 exp(-563±119/T) in cm 35 molecule s. A 3H3M2B atmospheric lifetime of 15 days towards the OH radical 36 was evaluated. Our results showed that the photolysis pathway is the major 37 degradation channel for 3H3M2B. Photolysis products were identified and quantified 38 in the present work with a carbon balance of around 80% enabling a reaction 39 mechanism to be proposed. The present work underlines the need for further studies 40 on the atmospheric chemistry of oxygenated VOCs. 41