The catalytic effect of H2O and six kinds of organic acids (e.g., formic acid) on the reaction of CH3CHOO with H2O is studied at the CCSD(T)//B3LYP/6-311+G(d,p) level. The results reveal that two possible channels exist as the double proton transfer and addition, of which the latter dominates for the non-catalytic reactions. For the additions, the OH of water is added to the α-C of CH3CHOO, and the H atoms migrate to the end oxygen atoms. Catalysts such as H2O and organic acid can form a hydrogen-bonded complex with CH3CHOO, which promotes the H transfer and thus significantly reduces the elementary reaction energy barrier and apparent activation energy when compared with that of the non-catalytic reaction. The catalytic effect is proportional to the strength of the organic acids. For example, for the formation of syn-HAHP catalyzed by H2O (pKa=15.7), formic acid (pKa=3.75) and oxalic acid (pKa=1.23), the energy barrier is reduced from 69.12 to 40.78, 18.88 and 10.61 kJ·mol-1, respectively. In addition, the non-catalytic reaction has a positive activation energy, whereas the catalytic reactions have an negative apparent activation energy.
Received: 18 July 2016
Published: 14 September 2016
Fund: The project was supported by the National Natural Science Foundation of China(21473108，21473107);Fundamental Research Funds for ShaanxiInnovative Team of Key Science and Technology, China(2013KCT-17);and Fundamental Research Funds for the Central Universities, China(JK201601005)