溴化苄及其阳离子红外光谱的理论研究

Theoretical study of the infrared spectra of benzyl bromide and its cation

利用密度泛函理论(DFT)在B3LYP/6-311G++(d,p)水平上对溴化苄分子进行了结构优化和频率计算,得到了该分子的稳定构型和全部振动模式.计算得到的几何参数通过与苯分子的实验值相比,发现理论值与其相吻合;理论计算和实验测得的红外光谱数据的比较分析表明,理论计算与实验测量结果符合得较好,并对其振动模式进行了归属.最后,在B3LYP/6-311G++(d,p)水平上计算得到了溴化苄阳离子的红外光谱,并与溴化苄进行了比较,计算表明电离对振动偶极距产生了较大影响.

By using density functional theory （DFT）, the geometry optimizations and frequency calcula- tions of benzyl bromide were performed at the B3LYP/6-311G＋＋ （d,p）level. The stable structure and complete vibrational modes of benzyl bromide were also attained. The calculated geometric parameters are in good agreement with the reported experimental measurement of benzene. When comparing the cal- culated IR data with those reported by experiments, it is found that the calculated results are in good a- greement with the experimental values. The vibrational modes of benzyl bromide molecule were as- signed. Finally, the infrared spectra of benzyl bromide cation were also calculated at the B3LYP/6-311G ＋ ＋ （d,p）level and the results were compared with those of benzyl hromide. The comparison shows that the ionization has a great influence on the vibration dipole moment.