12.1 : アルデヒドとケトンの構造

The distinct smell of vanilla and nail polish remover is derived from a class of carbonyl compounds called aldehydes and ketones.

In aldehydes, the carbonyl group is connected to one side group and one hydrogen atom; in ketones, it is bonded to two side groups and no hydrogen atoms.

The carbonyl group is sp²-hybridized, and the sigma bonds are about 120° apart.

Carbon’s unhybridized p orbital and oxygen’s 2p orbital overlap to give the π bond in the carbonyl group.

The electronegativity of the attached oxygen atom makes the carbonyl bond significantly polar, with the positive charge centered around the carbon atom and the negative charge around the oxygen atom.

The resonance structure further confirms the charge separation in the carbonyl bond. Polarization of the bond makes the carbonyl carbon electrophilic and the carbonyl oxygen nucleophilic.