Impact of the Water Molecule on the Gas-Phase Reaction between Acetone and Cl Atoms

The role of the water molecule in the atmospheric reaction between CH3COCH3 and Cl atoms was investigated at the theoretical level of CCSD(T)/aug-cc-pVTZ//BHandHLYP/aug-cc-pVDZ. The reaction between acetone and Cl atoms proceeds through three paths: an H-abstraction reaction, a -CH3 abstraction reaction, and an addition/elimination reaction by Cl, leading to the formation of CH3COCH2 + HCl (+H2O), CH3CO + CH3Cl (+H2O), and CH3COCl + CH3 (+H2O), respectively. The formation pathway of CH3COCH2 + HCl in the three paths occupies a dominant position, with a rate constant of 1.08 x 10(-12) cm(3) molecule(-1) s(-1). However, water-assisted CH3COCH3 + Cl reactions become more complex, proceeding through 10 different paths. At 298 K, the effective rate constant for CH3COCH2 + HCl + H2O formation is 8.46 x 10(-1)5 cm(3) molecule(-1) s(-1), and the effective rate constant decreases by 3-4 orders of magnitudes in the temperature range of 216.69-298.15 K. Therefore, it is concluded that water exerts a hindering effect on the CH3COCH3 + Cl + H2O reaction under atmospheric conditions, but it is not enough to change the dominant position of the CH3COCH3 + Cl reaction under anhydrous conditions.