4-Anisaldehyde

4-Anisaldehyde, or p-Anisaldehyde, is an organic compound with the formula CH₃OC₆H₄CHO. The molecule consists of a benzene ring with a formyl and a methoxy group. It is a colorless liquid with a strong aroma. It provides sweet, floral and strong aniseed odor. Two isomers of 4-anisaldehyde are known, ortho-anisaldehyde and meta-anisaldehyde. They are less commonly encountered.

Production

Anisaldehyde is prepared commercially by oxidation of 4-methoxytoluene using manganese dioxide to convert a methyl group to the aldehyde group. It can also be produced by oxidation of anethole, a related fragrance that is found in some alcoholic beverages, by oxidative cleavage of an alkene.

Uses

Being structurally related to vanillin, 4-anisaldehyde is widely used in the fragrance and flavour industry. It is used as an intermediate in the synthesis of other compounds important in pharmaceuticals and perfumery. The related ortho isomer has a scent of liquorice.
A solution of para-anisaldehyde in acid and ethanol is a useful stain in thin layer chromatography. Different chemical compounds on the plate can give different colors, allowing easy distinction.