Carboxylic acids and derivatives
Naming carboxylic acids and derivatives: Exercises
How to name carboxylic acids, esters, amides and acyl chlorides: -oic acid, the two words of an ester, N-substituents, with exercises and worked answers.
Carboxylic acids contain the –COOH group. Replacing its OH by another group gives the acid derivatives: esters (–COO–R), amides (–CONH2) and acyl chlorides (–COCl). All of them are named from the acid.
The rules you need
- Acids: the alkane name plus -oic acid. The COOH carbon is C1 of the chain and needs no locant: propanoic acid, 2-methylpropanoic acid. An acid group at each end gives -dioic acid: butanedioic acid.
- Esters are two words: first the group bonded to the single-bonded oxygen, then the acid part with -oate: methyl propanoate is made from propanoic acid and methanol.
- Amides: -oic acid becomes -amide. Groups on the nitrogen take the locant N: propanamide, N-methylpropanamide.
- Acyl chlorides: -oic acid becomes -oyl chloride: propanoyl chloride.
- These groups outrank aldehydes, ketones, alcohols and amines, which then become prefixes: 3-oxobutanoic acid. On a ring the acid is named with -carboxylic acid (cyclohexanecarboxylic acid), and on benzene it is benzoic acid.
Two names, read step by step
Ethyl propanoate
Split the ester at the single-bonded oxygen. The side with the C=O has three carbons, counting the C=O carbon: propanoate. The group on the other side of the oxygen has two carbons: ethyl. With the two groups the other way around, the name would be propyl ethanoate, a different compound with the same formula.
Propanamide
Three carbons, the last of which carries both the C=O and the NH2: propanamide. The amide carbon is C1 and needs no locant. Without the C=O the compound would be an amine, propan-1-amine.
Watch out for
- The carbon of COOH, COO–, CONH2 and COCl is part of the chain and is counted in the name.
- In an ester, the group named first is on the oxygen, not on the C=O carbon.
- An amide's N-methyl group is bonded to nitrogen; a methyl group on carbon would make a different amide.
Draw from the name: 19 exercises
Each name opens its exercise. Draw the structure and check it: any correct drawing is accepted, and hints and a worked answer help when you are stuck.
- propanoic acid Beginner
- ethyl ethanoate Beginner
- ethanoic acid Beginner
- butanoic acid Beginner
- methyl ethanoate Beginner
- ethanamide Beginner
- methyl propanoate Intermediate
- propanoyl chloride Intermediate
- 2-methylpropanoic acid Intermediate
- propyl ethanoate Intermediate
- ethanoyl chloride Intermediate
- N-methylpropanamide Intermediate
- cyclohexanecarboxylic acid Intermediate
- N,N-dimethylethanamide Advanced
- butanedioic acid Advanced
- propanedioic acid Advanced
- methyl 2-methylpropanoate Advanced
- prop-2-enoic acid Advanced
- 3-oxobutanoic acid Advanced
Name the structure
19 structures of this family to name, each with four names to choose from and an explanation of every wrong choice.
Printable worksheet
For practice on paper: names to draw and structures to name, with an answer key to check your work.
The full guide
The guide Carboxylic acids and derivatives explains these names in more detail, with more worked examples and the most common mistakes.