Vibrational spectra methylene groups

Estimate the frequencies of the peaks in the IR spectrum of methylene chloride shown in Figure 26F-2. From these frequencies, assign molecular vibrations of methylene chloride to each of the peaks. Notice that some of the group frequencies that you will need are not listed in Table 26-5, so you will have to look elsewhere. 

The guar gum (Figure 31.19) shows a less complex spectrum. Region II is represented by a unique peak at 3326 cm specific to OH stretching vibrations and a peak at 2898 cm corresponding to C-H stretching of methyl or methylene groups. 

The IR and Raman spectra of polyvinyl acetate are provided in Reference Spectrum 10. Key features of the IR spectrum of PVAc are the C=0 stretching vibration at 1740 cm , the C—O stretching vibration of the ester group at 1230 and 1020 cm , an absorption due to methyl CH bending at 1375 cm , and CH2 bending (scissors) vibration of the methylene groups at 1440 cm . An important copolymer of vinyl acetate is ethylene-vinyl acetate copolymer, EVA. For this copolymer, an increase in the number of —CH2— groups, due to the insertion of ethylene molecules into the polymer... 

---