posted on 2022-01-31, 22:14authored byYouqing Yu, Li Pan, Haihong Xiong, Xiaohua Xie, Qinqin Zhang, Qiyao Sun, Jie Wang, Dongsheng Liu, Binfang Yuan, Shimin Ding
The atmospheric degradation mechanism
of dicarboxylic acids (DCAs)
initiated by hydroxyl radicals has been theoretically investigated
at the DLPNO-CCSD(T)/def2-TZVP//BH&HLYP/6–311++G(d,p) level
of theory. In the presence of O2, the degradation of DCAs
by hydroxyl radicals takes place through a two-step mechanism: the
α-H elimination and the degradation of the peroxyl radical intermediate.
The latter degradation mechanism is easy to proceed for the exothermic
process of radical recombination. Therefore, the degradation rate
of DCAs is determined by an α-H elimination step, which is accelerated
in the case of long carbon-chain DCAs with a lower energy barrier.
Canonical variational transition state theory has been employed to
estimate the rate constants of the H-elimination step of the DCA degradation
reaction by hydroxyl radicals over the temperature range of 220–1000
K.