Band assignments group frequencies

The next step in assigning group frequencies is to establish the constancy of position of the group frequency in a series of related molecules. It has been reported [ ] that for amides a band near 1408 cm is indicative of the N—CH3 bend. Thus, it appears that for amides a band near 1410 cm is a group frequency of the N—CH3 group. 

No bands corresponding to free hydroxyl group were found. Instead, broad bands of low frequency (S450-3330 cm-1 and low intensity assigned to bonded OH groups were observed. 

Relative initial rates of polymerization of aliphatic aldehydes catalyzed by [Me2A10CPhNPh]2 catalyst followed the order of MeCHO > EtCHO > nPrCHO > i PrCHO (Fig. 9). It is apparent from the order that the rate of polymerization is lower when the alkyl group of aldehyde monomer is bulkier. It is conceivable that the steric factor, not the ionic factor, is predominant for the relative rates of polymerization, because the frequencies of IR bands assigned to the carbonyl group are nearly constant for these aldehydes. 

Few complete infrared spectra have been reported for the aza-indoles, although some partial band assignments have been made. In most cases, only the functional group frequencies of substituted azaindoles were reported. 

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