CH_2=CHCOOCH_3与O_3反应机理及速率常数的理论研究

Computational study on the reaction mechanism and kinetics of CH_2=CHCOOCH_3 ozonolysis

采用CBS-QB3方法构建了丙烯酸甲酯(CH_2=CHCOOCH_3)与O_3反应体系的势能剖面并在此基础上利用经典过渡态理论(TST)和Wigner矫正模型计算了标题反应在200K^1200K温度区间内的速率常数kTST/W.研究结果表明,CH_2=CHCOOCH)3与O)3反应首先经过渡态生成一个稳定的五元环中间体,然后按断键位置不同,分别生成产物P1(CH_3OCOCHO+CH_2O_2)和P2(CH)3OCOCHOO+HCHO).此外,速率常数结果显示,在计算温度范围内,标题反应速率常数呈正温度系数效应.294K时,CH_2=CHCOOCH_3与O_3反应速率常数为1.76×10-18cm^3·molecule^(-1)·s^(-1),与所测实验值(0.95±0.07)×10^(-18)cm^3·molecule^(-1)·s^(-1)非常接近.

The mechanism for the reaction between ozone and CH_2=CHCOOCH_3 was investigated at the CBS-QB_3 level of theory. The calculated results show that ozone adds to CH_2=CHCOOCH_3 via a fivemembered ring transition state to produce a highly unstable primary ozonide which can decompose readily to form P1（CH_3OCOCHO＋CH_2O_2） and P2（CH_3OCOCHOO＋HCHO）, respectively, due to the bond breaking in different position. The total rate constants are obtained by using the conventional transition state theory with Wigner tunneling correction in the temperature range of 200 K^1 200 K. The calculated result of rate constant（1.76×10^（-18） cm^3·molecule^（-1）·s^（-1） at 294 K） shows the title rate constant increases with the temperature increase, which is in good agreement with the experimental data of（0.95±0.07）×10-18 cm3·molecule^（-1）·s^（-1）.