NO_(2)硝化正己烷及其理论计算

Nitration of n-hexane with NO_(2) and theoretical calculation

对NO_(2)硝化正己烷的反应进行了研究,分别考察了反应温度、摩尔比和反应时间的影响。结果表明:在反应温度为120℃、正己烷与NO_(2)摩尔比为1∶2、反应时间为4h的反应条件下,正己烷转化率可达85.9%。通过密度泛函理论(DFT)研究了NO_(2)硝化正己烷的反应机理,在B3LYP/6-311++G(3df,2pd)//B3LYP/6-31G*计算水平下精确计算了三个可能反应途径的活化能(Ea)。计算结果表明:该反应决速步骤为NO_(2)中O原子进攻正己烷中的H原子,其中2-硝基己烷和3-硝基己烷为主要产物,且计算结果与实验结果一致。分子几何结构、原子电荷和IR振动频率的数据表明C—H键的断裂和N—H键的形成是一个协同过程,参与硝化反应的原子C(5)、H(7)、O(22)、O(23)和N(21)的分子几何参数及其原子电荷有明显的变化。

Effects of reaction conditions on the nitration of n-hexane with NO_(2) were systematically studied,including reaction temperature,mole ratio of n-hexane to NO_(2) and reaction time.The results showed that the conversion of n-hexane could reach 85.9%under the following reaction conditions:reaction temperature 120℃,mole ratio of n-hexane to NO_(2)1∶2 and reaction time 4h.Density functional theory(DFT)was used to study the reaction mechanism,the activation energies(Ea)of three possible reaction mechanisms were calculated at the B3LYP/6-311++G(3df,2pd)//B3LYP/6-31G*level.The calculated results are consistent with the experimental ones and further indicated that the crucial step of the process is the O atoms’attacking of the H atoms,and 2-nitrohexane and 3-nitrohexane are the main products.The data of molecular geometry,atomic natural charge and IR spectra showed that the breaking of C-H bond and the formation of N-H are cooperative.Obvious changes of molecular geometry and atomic natural charge happened to the atoms of C(5),H(7),O(22),O(23)and N(21),which all participated in the nitration process.