# Aldehyde and ketone nomenclature when aldehyde/ketone group is bonded to an alkyl group

The longest alkane chain is decane and, attached to the fifth carbon, is an ethyl group the end of which is double bonded to an oxygen atom. My best guess at naming it would be:
5-(ethyl-2-al)decane.

Here, the longest chain is again decane, but there is a propyl group and an oxygen atom double bonded not to the ends of the alkyl, but to carbon #2, which leads me to:

5-(propyl-2-one)decane

Now I have no clue as to whether I am right or not because I have never come across such molecules and I have just done what I found to be logical. Have I come to the correct conclusions?

• No, chain with functional group is more important – Mithoron Sep 1 '15 at 15:04
• @Mithoron So 3-butyl octane and 4-butyl nona-2-one? Why doesn't the longer chain take priority? – GeeJay Sep 1 '15 at 15:34
• Because there is a hierarchy of priority that starts with functional groups and ends with longest chains. – prooffreader Sep 1 '15 at 16:57

The characteristic group $\ce{=O}$ corresponds to the substitutive prefix ‘oxo’. Thus, the substitutive names that you are looking for are ‘5-(2-oxoethyl)decane’ and ‘5-(2-oxopropyl)decane’.