Atmospheric Degradation of 4-Hydroxy 4-Methyl 2-Pentanone with OH in the Gas Phase at 297 K

Abstract

The reaction of 4-hydroxy-4-methyl-2-pentanone (4H4M2P) with OH radicals was investigated in the gas-phase using an absolute rate method at room temperature and over the pressure range of 10 to 745 Torr in He and air as diluent gases. The rate coefficients were measured with the Pulsed Laser Photolysis method (PLP) to produce OH and the Laser Induced Fluorescence technique (LIF) to detect the fluorescence of OH radicals. An average value of (4.5±1.5)×10-12 cm3molecule-1s-1 was obtained. This study is the first absolute determination of the rate coefficient of 4H4M2P with OH at room temperature as a function of pressure and the nature of diluent gases. No pressure dependence of the rate coefficient was observed. The obtained results are compared with those of other hydroxyketones in terms of the structure reactivity relationship. The calculated tropospheric lifetime obtained in this work suggests that once emitted into the atmosphere, 4H4M2P may contribute to the photochemical pollution in a local or regional scale.