Theoretical investigation on degradation of CH[triple bond, length as m-dash]CCHOH by NO radicals in the atmosphere.

A detailed computational investigation is executed on the reaction between NO and CH[triple bond, length as m-dash]CCHOH at the CCSD(T)/cc-pVTZ//B3LYP/6-311++G(d,p) level. Addition/elimination and H-abstraction mechanisms are found for the NO + CH[triple bond, length as m-dash]CCHOH reaction, and they could compete with each other. The most feasible addition/elimination pathway through a series of central-C addition, 1,4-H migration to generate intermediates IM1 (CHCONOCHOH) and IM3 (CHCONOCHO), and then IM3 directly decompose into product P2 (CHCONOCHO + H). The dominant H-abstraction pathway is abstracting the H atom of the -CH- group to generate h-P1 (CHCCHOH + HNO). RRKM-TST theory was used to compute the kinetics and product branching ratios of the NO + CH[triple bond, length as m-dash]CCHOH reaction at 200-3000 K. The rate constants at 298 K are consistent with the experimental values. The lifetime of CH[triple bond, length as m-dash]CCHOH is estimated to be 59.72 days at 298 K. The implicit solvent model was used to examine the solvent effect on the total reaction. Based on the quantitative structure-activity relationship (QSAR) model, the toxicity during the degradation process is increased towards fish, and decreased towards daphnia and green algae.