Aldehydes are an organic compound that features a structure R-CHO, and consists of a carbon center that shows a carbon double bonded to oxygen, otherwise known as a carbonyl center. This carbonyl center is also bonded to hydrogen, as well as an R group, which can be any alkyl, generic or otherwise, or a side chain. They are in the formyl group; a functional group.
Aldehydes are similar, although notably different, to ketones. Aldehydes possess a carbonyl that lies at the end of their carbon skeleton, whereas ketones have theirs situated in between two carbon atoms. Many fragrances are, in fact, aldehydes, which makes their presence in perfumery extensive. Trace elements of aldehydes are evident in many essential oils, and have been found to often provide much of the essential oil’s aromas. Such cases include vanillin and cilantro. Many aldehydes hold commercial and productive applications in perfumery, often acting as precursors to alcohols. The aldehydes used extensively in perfumery are usually produced on a much smaller scale than those used in other fields. One notable example is the substance cinnamaldehyde, who’s derivatives are mainstays in perfumery: citral, and lilial.
Read more about aldeyhdes at the fragrance family aldehydics.