Theoretical studies on the mechanisms and rate constants for the hydroxylation of n-butyl, iso-butyl and tert-butyl vinyl ethers in atmosphere

The reaction mechanisms for the atmospheric hydroxylation of n-butyl vinyl ether (n-BVE), iso-butyl vinyl ether (i-BVE), and tert-butyl vinyl ether (t-BVE) were investigated by using quantum chemical method in this paper. The geometry optimizations and frequency calculations were carried out at the MPWB1K/6-31+G(d,p) level, and the accurate energetic parameters were obtained by the MPWB1K/6-311++g(3df,2p) method. The reaction mechanisms for the title reactions have been presented. Ten possible reaction channels were discussed for the primary hydroxylation of n-BVE and t-BVE, while fourteen pathways for i-BVE. Three favorable reaction pathways were chosen for each isomer to undergo further investigation. Major products are n-butyl formate, iso-butyl formate, tert-butyl formate, and HCHO. The rate constants of the primary reactions were calculated over the temperature range of 200-400 K and the pressure range of 100-2,000 Torr by employing MESMER program. At 298 K and 760 Torr, the whole rate constants of n-BVE + OH, i-BVE + OH, and t-BVE + OH are 12.3 x 10(-11), 9.32 x 10(-11) and 5.75 x 10(-11) cm(3) molecule(-1) s(-1), respectively. Additionally, the lifetimes of the three isomers with respect to OH radical are ((n-BVE)) = 1.13 h, ((i-BVE)) = 1.49 h, and ((t-BVE)) = 2.41 h.