Question

How do you name ketones?

Answer 1

The IUPAC (The International Union of Pure and Applied Chemistry) system of nomenclature assigns a characteristic suffix of -one to ketones (propanONE or acetONE, hexanONE,...)

1. First of all, a ketone carbonyl function may be located anywhere (chain or ring). Its position is usually given by a location number (2, 3, 4,...).

2. Chain numbering normally starts from the end nearest the carbonyl group. For example, very simple ketones (see picture) do not require a locator number, since there is only one possible site for a ketone carbonyl function.

3. The names for ketones are formed by naming both alkyl groups attached to the carbonyl then adding the suffix -one. Very important rule is that the attached alkyl groups are arranged in the name alphabetically.

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As with many molecules with two or more functional groups, one is given priority while the other is named as a substituent! It is very important to know that aldehydes have a higher priority than ketones.

4-oxopentanal

Molecules which contain both functional groups are named as aldehydes and the ketone is named as an -oxo substituent.
You should know that aldehyde is always at the end of the chain so it is not necessary to give the aldehyde functional group a location number. But, it is necessary to give a location number to the ketone. Except in very simple ketones (see picture) because there is only one possible site for a ketone carbonyl function.