Double bonds Raman frequencies

Table 7.7 lists double bond stretching frequencies (some from Raman data) of the 1,2-disubstituted cyclo-enes. Other positions as well as 1 and 2 may be substituted. 

In the case of vinyl acetate the carhonyl intensity in the Raman effect is difficult to relate to the aUphatic series, hut the band is significantly weaker than the double-bond stretching frequency near 1655 cm and the reverse of that found in the IR spectrum. The Raman band is in the medium to strong range. 

Table 7.32 Raman Frequencies of Cumulated Double Bonds...

TABLE 7.34 Raman Frequencies of Other Double Bonds Continued)... 

The analysis of relations between intensities in the region of double bond stretching vibrations >c=n in the Raman spectra, allows one to arrive at a conclusion about s-cis- or s-trans -conformation of multiple bonds. The ratio between intensities of the high-frequency band to the low-frequency one for s-trans -conformers appears usually to be more than 0.5, whereas for s-cis -conformers it is less than 0.25 (393, 394). 

Figure 1.13 Raman spectra for a number of transition metal oxides supported on y-AI203 [75,102], Three distinct regions can be differentiated in these spectra, namely, the peaks around 1000 cm-1 assigned to the stretching frequency of terminal metal-oxygen double bonds, the features about 900 cm 1 corresponding to metal-oxygen stretches in tetrahedral coordination sites, and the low-frequency (<400 cm-1) range associated with oxygen-metal-oxygen deformation modes. Raman spectroscopy can clearly complement IR data for the characterization of solid catalysts. (Reproduced with permission from The American Chemical Society.)...

Picosecond Raman measurements have led to the proposal of a dynamic polarization model." In this model, 5i tS undergoes reversible changes in vibrational frequencies that are induced by solvent fluctuations. The mixing of a perturbing state with interconverts carbon-carbon double bonds with single bonds that leads S tS near the vertical geometry to proceed along the pathway for isomerization. 

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