ABSTRACT
If the infrared spectrum is of a substituted benzene, taken as the neat liquid, if may also be possible to verify the substitution pattern on the ring by matching the overtone and combination bands. The position of the double bond in the spectra of cycloalkenes is influenced by ring strain. The greater the degree of strain, the lower the frequency of the C=C stretching vibration. Many of the band positions of amines, taken in the solid state are not always reliable, since they are often split and shifted from their expected positions. The various classes of carbonyl compounds, in addition to having their own unique spectral characteristics, can often be distinguished from each other by a precise measurement of their C=O stretching absorptions. The vibrational frequencies of bonds in organic compounds are influenced by electron-withdrawing and -donating effects. The decrease in frequency of the carbonyl absorption with conjugation can be explained on the basis of resonance.
