What are the guidelines for naming ketones?

Ketones are named by identifying the longest carbon chain, replacing the -e in alkane with -one, and numbering the carbonyl carbon.

In more detail, the first step in naming ketones is to identify the longest continuous carbon chain that contains the carbonyl group. This chain is named as if it were an alkane, but the ending -e is replaced with -one to indicate the presence of a ketone. For example, a three-carbon chain with a ketone group would be named propanone.

The next step is to number the carbon atoms in the chain, starting from the end nearest to the carbonyl group. The carbonyl carbon (the carbon atom double-bonded to the oxygen) is given the lowest possible number. For example, in a five-carbon chain with the ketone group on the second carbon, the molecule would be named 2-pentanone.

If there are other functional groups or side chains present, these are named and numbered as substituents. They are listed in alphabetical order before the name of the main chain. For example, a four-carbon chain with a ketone group on the second carbon and a methyl group on the third carbon would be named 3-methyl-2-butanone.

Remember, the carbonyl group in ketones is always located somewhere within the carbon chain, not at the end. This differentiates ketones from aldehydes, which have a carbonyl group at the end of the chain. It's important to keep this distinction in mind when naming these compounds.