红外拉曼光谱(英文)IR_Raman.ppt

Instrumental Analysis Infrared and Raman Spectroscopy Group Frequencies and Complimentary Natures Raman and IR Transitions Selection Rule for Absorption of Light in IR Must be change in dipole moment Polar groups such as OH, C=O, P=O, S=O and NO2 are stronger absorbers Asymmetric (anti-symmetric) stretching vibrations are stronger than symmetric stretching vibrations Selection Rule for Raman Scattering Must be change in polarizability Non-Polar groups such as C-S, S-S, C=C, C?C (triple bond), N=N and heavy atoms (I, Br, Hg) strong scatterers Symmetric stretching vibrations are much stronger scatterers than asymmetric stretching vibrations Predicted Frequencies Effect of Mass Increases Effect of Increasing Number of Bonds Carbon-Carbon Double Bonds Olefin Vibrations Olefin Spectra X-H vibrations O-H Vibrations O-H / N-H Spectra Multiple bond Vibrations Chloro-acetonitrile Spectra Carbonyl Vibrations Fingerprint Vibrations Aromatic Substitutions More Fingerprint Vibrations C-O- Vibrations * IR Absorptions Raman -C=C- -S-H -C=C- -CH2 wag Trans -CH2 wag =CH2 st -CH2 st -CH2 bend OH / NH Stretches CH2 Stretches C=O Stretch S-S Stretch Anti-sym Sym C?N Stretch C-Cl Stretch CH2 Stretch Sym Anti-Sym CH2 Stretch Sym Anti-Sym