Group frequencies stretching

Infrared spectroscopy is an excellent tool in iminoborane chemistry, which readily permits, to distinguish between iminoboranes and nitrile-borane adducts and to identify monomeric and dimeric forms of iminoboranes. This event is due to the fact that the i>CN of CN multiple bonds absorbs outside the fingerprint region and can be considered to be a valuable group frequency even when mixed with other vibrational modes. In some cases other vibrations like NH, BH, B-halogen or B-S stretching modes are helpful for determining the structure of iminoboranes. 

Table 22.1 Stretching Frequencies found in Group Frequency Region...

As seen from the data in Table 7-4 (abstracted from frequencies provided in Appendix A7) symmetric methyl group CH stretching frequencies change with substitution. The smallest value is for methylamine (chosen as the reference compound) and the largest is for methyl chloride. (Ethane has been excluded from this comparison as the symmetric stretch here involves all six hydrogens.)... 

Table 7-4 Symmetric Methyl Group CH Stretching Frequencies in CH3X Molecules ... 

Useful characteristic group frequency bands often involve coupled vibrations. The spectra of alcohols have a strong band in the region between 1260 and 1000 cm-1, which is usually designated as the C—O stretching band. In the spectrum of methanol this band... 

Functional group Frequency (C=0 stretch), cm-1 Functional group Frequency (0=0 stretch), cm ... 

P=0 Thomas and Chittenden (5,38 441 have carried out a thorough series of studies on the identification of organophosphorus compounds. The group frequency tables in these studies enable interpretation of many of the characteristic features in the spectra of nerve agents and related chemicals. Several structure-spectrum relationships give specific information on the molecule. One very valuable relation discovered by Thomas is the dependence of the position of the P=0 bond stretching vibration, vp=0, on the substituents on the phosphorus, represented by n constants ... 

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