Aldehydes are organic compounds containing formyl functional group, in which the carbonyl carbon is attached to a hydrogen atom and an R group. The R group may be an alkyl or aryl group. Aldehydes are formed by replacing hydrogen atom of a hydrocarbon by the formyl group. The flavours of Almond, vanilla beans and cinnamon are due to the presence of aldehyeds.
This video explains how to identify aldehydes using some simple tests.