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

By using density functional theory(DFT),the geometry optimizations and frequency calculations 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 calculated IR data with those reported by experiments,it is found that the calculated results are in good agreement with the experimental values.The vibrational modes of benzyl bromide molecule were assigned.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 bromide.The comparison shows that the ionization has a great influence on the vibration dipole moment.