The mechanism and kinetics of the production of hydroxymethyl hydroperoxide (HMHP) in ethene/ozone/water gas-phase system were investigated at room temperature (298±2 K) and atmospheric pressure (1×105 Pa). The reactants were monitored in situ by long path FTIR spectroscopy. Peroxides were measured by an HPLC post-column fluorescence technique after sampling with a cold trap. The rate constants (k 3) of reaction CH2O2+H2O→HMHP (R3) determined by fitting model calculations to experimental data range from (1.6?6.0)×10?17 cm3·molecule?1·s?1. Moreover, a theoretical study of reaction (R3) was performed using density functional theory at QCISD(T)/6-311+(2d,2p)//B3LYP/6-311+G(2d,2p) level of theory. Based on the calculation of the reaction potential energy surface and intrinsic reaction coordinates, the classic transitional state theory (TST) derived k 3 (k TST), canonical variational transition state theory (CVT) derived k 3 (k CVT), and the corrected k CVT with small-curvature tunneling (k CVT/SCT) were calculated using Polyrate Version 8.02 program to be 2.47×10?17, 2.47×10?17 and 5.22×10?17 cm3·molecule?·s?1, respectively, generally in agreement with those fitted by the model.
Acetone plays an important role in photooxidation processes in the atmosphere. Up to date, little is known regarding the heterogeneous fate of acetone. In this study, the adsorption and desorption processes of acetone on SiO2 particles, which are the major constituent of mineral dust in the atmos-phere, have been investigated for the first time under the simulated atmospheric conditions, using in situ transmission Fourier transform infrared spectroscopy. It is found that acetone molecules are ad-sorbed on the surfaces of SiO2 particles by van der Waals forces and hydrogen bonding forces in a nonreactive and reversible state. The rates of initial adsorption and initial desorption, initial uptake coefficients and adsorption concentrations at equilibrium have been determined at different relative humidity. The presence of water vapor cannot result in the formation of new substances, but can de-crease the adsorption ability by consuming or overlapping the isolated OH groups on the surfaces of SiO2 particles. In the desorption process, a considerable amount of acetone molecules will remain on SiO2 particles in dry air, whereas acetone molecules are almost completely desorbed at a high relative humidity. In order to evaluate the role of heterogeneous reactions of acetone and other carbonyl compounds in the atmosphere, a new model fitting the atmospheric conditions is needed.
JIE ChongYu CHEN ZhongMing WANG HongLi HUA Wei WANG CaiXia LI Shuang
