中文摘要：

采用B3LYP/6-311＋＋G（3df,2pd）//B3LYP/6-31＋G（d,p）双水平方法对2-甲基噻吩与NO3的反应机理进行了理论研究.研究结果表明,标题反应主要存在抽氢、SN2取代和加成-消去反应3种类型,共10条反应通道.其中SN2取代和加成-消去反应通道所需能垒均较高,反应不易进行,而在抽氢反应中R4所需能垒仅为6.77kJ/mol,为标题反应的主通道.采用经Wigner校正的经典过渡态理论计算得到抽取甲基氢通道（R4）在298K时的速率常数为1.03×10^-13 cm-3/（molecule·s）,与Caba珘nas测定的实验值（7.21×10^-13 cm^3/（molecule·s））接近.

英文摘要：

The reaction mechanism of 2-metyhlthiophene with NO3 radical have been investigated at the B3LYP/6-311＋＋G（3df,2pd）//B3LYP/6-31＋G（d,p）level of theory.The results show that the title reaction mainly includes hydrogen abstraction, SN 2 substitution and addition-elimination reactions.The barriers of SN 2 substitution and addition-elimination are higher than the hydrogen abstraction reactions,in which the barrier of R4 is equal to 6.77 kJ/mol and it is a dominant pathway in the title reactions. The rate constant for the dominant channel R4 is calculated with conventional transition state theory （TST）at 298 K,where Wigner method is adopted to correct the quantum mechanical tunneling effect.The calculated value is 1.03×10^-13 cm^3/（molecule·s）,which is consistent with Cabanas′s result （7.21×10^-13 cm^3/（molecule·s）） by using laser induced fluorescence method.