Answer to Question #74430 in Organic Chemistry for Kamal

Question

Carbonyl compounds absorb radiation in the infrared region. Give reason.

Answer 1

The carbonyl is a polar functional group that frequently is the most intense peak in the spectrum.
carbonyl compounds absorb in the region 1760-1665 cm-1 due to the stretching vibration of the C=O bond. This distinctive carbonyl band is particularly useful for diagnostic purposes because it has a characteristic high intensity and few other functional groups absorb in this region. Different carbonyl compounds absorb in narrow ranges within the general carbonyl region.
The exact wavenumber of the C=O stretch can give you clues as to whether the compound is a ketone, aldehyde, ester, or carboxylic acid;
range type of compound
1750-1735 cm-1 saturated aliphatic esters
1740-1720 cm-1 saturated aliphatic aldehydes
1730-1715 cm-1 α, β-unsaturated esters
1715 cm-1 saturated aliphatic ketones
1710-1665 cm-1 α, β-unsaturated aldehydes and ketones