Identification of the raman characteristic spectrum vibrations for various PAEs based on benzene solvent effect

By means of density functional theory and self-consistent reaction field in B3LYP/6-311G(d) method, the 16 kinds of phthalate esters (PAEs): BBP,DBP,DCHP,DEHP,DEP,DIDP,DINP, DMP, DNOP, BMPP, DAP, DHP, DIPrP, DMEP, DPhP and DPP were selected and their structures were optimized. Their Raman vibrational frequencies and depolarization in atmosphere and 6 kinds of solvents were calculated. The results show that Raman vibrations of 16 PAEs are assigned to ring deformation,ester base deformation,C-C stretching,C-H wiggle,C-H stretching and of these several patterns. The peak position of the ester base functional group is relatively fixed in 1 700-1 780 cm-1. Raman peak of ester base vibration is stronger,and the polarization degree is lower (the symmetry of vibration was stronger). Therefore, the ester base vibration can be regarded as the characteristic vibration. But the minimum differential wave numbers of only 12 kinds of PAEs are larger than micro Raman spectrometer detection limit (0.2 cm-1), so the 16 kinds of PAEs can not be fully identified by depolarization and the Raman peak of ester base vibration frequency area. Solvent effect analysis shows that benzene solvent has obvious enhanced solvent effects on 16 kinds of PAEs. The minimum differential wave numbers of 16 kinds of PAEs increase to 0.2 cm-1 above and the Raman intensity increases to 23%-183%,which illustrate that the 16 kinds of PAEs can be fully identified by depolarization and the Raman peak of ester base vibration frequency area. It provides theoretical basis for the detection of PAEs Raman spectroscopy. ©, 2015, Chines Academy of Sciences. All right reserved.