∞ generated and posted on 2016.01.10 ∞

Organic molecule characterized by the presence of a carbonyl group associated with an end carbon.

Aldehydes can be contrasted with ketones where the carbonyl group instead is associated with a middle carbon. Thus, O=C'-C''-C''' shows a carbonyl group, an end carbon (C'), a middle carbon (C''), and another end carbon (C''') and this molecule is an aldehyde because C' is an end carbon (note however that not all bonds or atoms found in this molecule are shown).

Sugars that are aldehydes are known as aldoses. Perhaps not coincidentally, aldehydes tend to be sweet to the taste (though not all sugars are aldoses, that is, contrast ketose though note that ketones, too, taste sweet). Aldehydes additionally are perceived as fragrant, i.e., such as may be found used in perfumes.