A theoretical study on gas-phase reactions of acrylic acid with chlorine atoms: mechanism, kinetics, and insights

Chlorine atoms initiated oxidation reactions are significant for the removal of typical volatile organic compounds (VOCs) in the atmosphere. The intrinsic mechanisms of CH2=CHCOOH + Cl reaction have been carried out at the CCSD(T)/cc-pVTZ//M06-2X/6-311++G(d,p) level. There are hydrogen abstraction and C-addition pathways on potential energy surfaces. By analyses, the addition intermediates of IM1(ClCH2CHCOOH) and IM2(CH2CHClCOOH) are found to be dominant. The secondary reactions of IM1 and IM2 have been discussed in the presence of O3, O2, NO, and NO2. And we have also investigated the degradation mechanisms of ClCH2CHO2COOH with NO, NO2, and self-reaction. Moreover, the atmospheric kinetics has been calculated by the variable reaction coordinate transition–state theory (VRC-TST). As a result, the rate constants show negative temperature and positive pressure dependence. The atmospheric lifetime and global warming potentials of acrylic acid have been calculated. Overall, the current study elucidates a new mechanism for the atmospheric reaction of chlorine atoms with acrylic acid.