Naming Carbonyl Compounds
Introduction
The following are common carbonyl compounds. A ketone has two carbon groups attached to the carbonyl while an aldehyde has a carbon group and a hydrogen atom attached to the carbonyl group. A carboxylic acid has an OH group attached to the carbonyl. Esters, amides, and acid chlorides are carboxylic acid derivatives. As we will see later in this chapter, they can all be made from carboxylic acids. Esters have alkoxy groups (–OR) attached to the carbonyl, amides have nitrogen atoms attached to the carbonyl, and acid chlorides have chlorine atoms attached to the carbonyl.
Nomenclature
Ketones
IUPAC
Ketone are named by using the suffix –one. The longest alkane chain is identified. The –e suffix is dropped from the alkane name and –one is added.
Common
The common way to name ketones is to name the two alkyl groups of the ketone in alphabetical order followed by the suffix –ketone. Methyl ethyl ketone (MEK) is an exception to the alphabetical rule but it is still commonly used for historical reasons. A ketone that is a very common solvent is 2-propanone. The name 2-propanone might be correct for an IUPAC name, but it is never used. This solvent is universally called acetone. It is used as a fingernail polish remover as well as many other things.
Aldehydes and Carboxylic Acids
IUPAC
Aldehydes are named by using the suffix –al. The longest alkane chain is identified. The –e suffix is dropped from the alkane name and –al is added. Numbering for aldehydes begins at the carbonyl. The carbonyl carbon atom is #1. Carboxylic acids are named much the same way, except instead of having the –al suffix, they have the –ic acid suffix or –oic acid suffix.
Common
Aldehydes are sometimes named using the common name for the parent carbon chain followed by the suffix -aldehyde. Carboxylic acids use the common parent name followed by –ic acid. The common name for the parent carbon chain is used in the common names for both aldehydes as well as carboxylic acids.
Common names for carboxylic acids and aldehydes
Amides
Amides are named by looking at the carboxylic acid name and replacing the –ic acid or –oic acid suffix with –amide.
If there are substituents on the nitrogen atom of the amide, we can put a capital “N” before the substituent to indicate the substituent is attached to the nitrogen atom.
Cyclic amides are called lactams. Penicillin is a famous lactam.
Esters
We saw that one-way esters can be made is from the reaction of an alcohol with a carboxylic acid under acid catalyzed conditions (a Fischer esterification).
To name esters, we first name the alkyl group from the alcohol part of the ester first. We follow that with the carboxylate part of the ester (from the carboxylic acid) followed by the suffix –ate. Remember, name the alcohol part first and the carboxylic acid part last.
Cyclic esters are called lactones.
