Nomenclature of Aldehydes and Ketones

Aldehydes and ketones both carry the carbonyl group (>C=O) and are named by the same IUPAC machinery used for other organic families: find the longest carbon chain that includes the carbonyl carbon, replace the alkane's '-e' ending with '-al' for an aldehyde (the carbonyl carbon is always numbered C1, since it must sit at the end of the chain) or '-one' for a ketone (the carbonyl carbon gets the lowest possible locant, cited before the '-one' suffix, since it can sit anywhere along an interior chain). Common names remain in wide use alongside IUPAC names -- formaldehyde (methanal), acetaldehyde (ethanal), acetone (propanone), benzaldehyde (phenylmethanal) -- and are built the same way common names of acids are (see 12.8), by simply substituting a family-ending onto the familiar trivial root. Substituent prefixes (chloro, hydroxy, oxo, phenyl, alkyl branches) are cited exactly as for any other IUPAC name, each with its own locant, and a second carbonyl group present as a substituent elsewhere on the chain is cited as an 'oxo-' pre …