The IUPAC names of open chain aliphatic aldehdes and ketones are derived from the names of the corresponding alkanes by replacing the ending -e with -al and - one respectively. In case of aldehydes the longest carbon chain is numbered starting from the carbon of the aldehyde group while in case of ketones the numbering begins from the the end nearer to the carbonyl group. The substituents are prefixed in alphabetical order along with numberals indicating their positions one . when the aldehyde group is attached to a ring, the suffix carbaldehyde is added after the full name of the cycloalkane. The numbering of the ring carbon atoms start from the carbon atom attached to the aldehyde group. The name of the simplest aromatic aldehyde carrying the aldehyde group on a benzene ring is benzenenecarbaldehyde. However, the common name benzaldehyde is also accepted by IUPAC. Other aromatic aldehydes are hence named as substituted benzaldehydes. How is the carbon chain numbered in case of ketones according to IUPAC nomenclature ?