Chemistry » Organic Molecules » IUPAC Naming And Formulae

Naming Esters

Naming esters

When an alcohol reacts with a carboxylic acid an ester is formed. A new bond is formed between the oxygen atom of the hydroxyl group and the carbonyl carbon atom of the carboxylic acid. The suffix for an ester is -oate.

Naming Esters

The esterification process of ethanol and butanoic acid to ethyl butanoate and water

Naming Esters

The (a) structural, (b) condensed structural and (c) molecular formula representations of ethyl butanoate. (d) An atomic model of ethyl butanoate.

 . Naming Esters 

Although the part of the ester from the alcohol (ethyl) is on the right, and the part from the carboxylic acid (butan-) is on the left in the figure below, when naming the structure the part of the name from the alcohol is written first (ethyl butanoate). Don’t forget to count the carbon atom in the carbonyl group when determining the number of carbon atoms in the chain.

Naming Esters

The (a) structural, (b) semi-structural structural and (c) condensed structural representations of \(\color{red}{\textbf{ethyl}}\color{orange}{\textbf{ butanoate}}\). 

Example:

Question

Give the IUPAC name for the following compound:

Naming Esters

Identify the functional group

There is a \(-\)C\(=\)O (carbonyl) group as well as an oxygen atom bonded to the carbon atom of the carbonyl and another carbon atom. This is therefore an ester and the suffix is -oate.

Determine which part is from the alcohol and which is from the carboxylic acid

An ester is a carboxylic acid derivative. Divide the molecule in two with the carbonyl group on one side and the oxygen bonded to two carbon atoms on the other.

Naming Esters

The part containing the oxygen atom bonded to two different carbon atoms was formed from the alcohol and is on the left here. The part containing the carbonyl group was formed from the carboxylic acid and is on the right here.

Naming Esters

Number the carbon atoms on the carbon chains

There is only one carbon atom in the left-hand chain (from the alcohol). Therefore this will be methyl. There are three carbon atoms in the right-hand chain (from the carboxylic acid) therefore the prefix will be propan-.

Combine the elements of the compound’s name into a single word in the order of chain from the alcohol; prefix (from chain containing carbonyl functional group), name ending according to functional group

The compound’s name is methyl propanoate.

Example:

Question

Draw the structural and condensed structural representations for the organic compound ethyl hexanoate.

Identify the functional group

The compound has the suffix -oate. It is therefore an ester and has a \(-\)C\(=\)O (carbonyl) group as well as an oxygen atom bonded to the carbon atom of the carbonyl and another carbon atom.

Determine which part is from the alcohol and which is from the carboxylic acid

The ethyl tells us that there are two carbon atoms in the part of the chain from the alcohol. The prefix hex- tells us that there are six carbon atoms from the part of the chain from the carboxylic acid.

Naming Esters

Place the functional group as well as any branched groups

The oxygen atom bonded to two different carbon atoms is located between the two sections. The \(-\)C\(=\)O (carbonyl) group is located at the first carbon atom of the carboxylic acid chain.

Naming Esters

Combine this information and add the hydrogen atoms

Naming Esters

Condense the structural representation

Condense the part of the compound that came from the carboxylic acid first, so start from the right here: \(\text{CH}_{3}\text{CH}_{2}\text{CH}_{2}\text{CH}_{2}\text{CH}_{2}\text{COO}\)

The first O is for the \(-\)C\(=\)O, the second is from the \(-\text{O}-\). Now condense the part that came from the alcohol, starting from the \(-\text{O}-\):

\(\text{CH}_{3}\text{CH}_{2}\text{CH}_{2}\text{CH}_{2}\text{CH}_{2}\text{COOCH}_{2}\text{CH}_{3}\)

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