The Intensities of Carbonyl Absorptions

Characteristic ketonic frequencies other than the C=0 stretching absorption 

The presence of the carbonyl group in a molecule often gives rise to the appearance of a medium intensity band in the single bond stretching region, in addition to the carbonyl absorption itself. Had2i and Sheppard [49] have observed a strong band between 1350 cm  

One other possibility for the identification of ketones is the deformation vibration of the C=0 group. The group —CO—CH3 gives rise to three bands associated with this mode [51], near 600, 500 and 400 cm , but considerable alterations follow chain branching if this occurs near to the carbonyl group, so that the bands cannot be identified in methyl zsopropyl ketone. This correlation is therefore mainly of academic interest. 

Less information is available for aldehydes than for ketones, but such evidence as there is indicates that the factors influencing frequency shifts are very much the same in both cases. 

Chelation effects in -hydroxy-a -unsaturated aldehydes are also 

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Methacrylic anhydride was prepared from methacroyl chloride and either sodium methacrylate (14) or methacrylic acid (15). The relative intensity of resonance observed at 6=11.6 ppm in the nmr spectrum of this monomer and the intensity of carbonyl absorption observed at 1700 cm-1, relative to that observed at 1724 and 1782 cm-1 Indicated that the monomer had less than 3 mole percent methacrylic acid. For the most part, monomer used for copolymerization experiments, b.p. 50° (1 mm), was prepared from sodium methacrylate. It contained less than one mole percent methacrylic acid ... 

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