Naming Carboxylic Acids | IUPAC Nomenclature

There are rules to follow in naming carboxylic acids according to the IUPAC nomenclature system. General organic IUPAC nomenclature rules are applied for carboxylic acids too. So we have to follow those rules with few new rules of carboxylic acids. nomenclature. In this tutorial, we discuss lot of examples to understand the nomenclature of carboxylic acids perfectly.

Carboxylic acid group

You know in carboxylic acids, the -COOH group is always exists at the end of the carbon chain.

IUPAC names and general names of some carboxylic acids

As IUPAC names, general names also mentioned with brackets. You can see, there is a patteren in every IUPAC name of carboxylic acid compounds. Those names end with the 'oic acid' term. That means, when you write the IUPAC name of carboxylic acid, you should end the name with 'oic acid'.

• HCOOH - methanoic acid (Formic acid)
• CH₃COOH - ethanoic acid (acetic acid)
• Ph-COOH - Phenylmethanoic acid (benzoic acid)

General Rules

1. Choose the longest carbon chain which contains carboxylic group. If double bonds or triple bonds exit, they should be included to the chain.
2. Give number 1 to the carboxylic acid carbon atom and number the carbon chain.
3. Name of carboxylic acid should be end with oic acid and there should be a space between oic and acid. No need to write number 1 in front of oic acid suffix.
   
   
   
4. Other substitution groups, branch chains can be named using general IUPAC nomenclature rules.

Examples of carboxylic acid names

Now we are going to discus some carboxylic acid naming examples.

Ethanoic acid

In ethanoic molecule, there is only two carbon atoms. So eth suffix will come and there is no any substituted group. Hence name the molecule as ethanoic acid.

But-2-enoic acid

See but-2-enoic acid molecule. It contains four carbon atoms with one double bond. Carbon bond numbering should be started from carboxylic carbon atom. Therefore double bond gets the number 2. First, alkene group (substitution part) should be written as but-2-en. Next, oic acid should be in the end of the but-2-en.

Naming carboxylic acids when aldehyde group exists

If aldehyde group exist in the major chain

Aldehyde group should be named as oxo as a substitution group

When aldehyde group exists as a substituted group

When aldehyde group is not in the main chain (when aldehyde group does not have a number in main chain), these aldehyde group are named as Formyl.

When a ketone group is attached

Any ketone group is named as oxo in carboxylic acid naming.

CH₃C(CH₃)₂CH₂COOH

Number the carbon chain starting from carboxylic acid carbon. There are two substitute methyl groups which are connected to the 3^rd carbon atom. In the main chain, there are four carbon atoms.

Naming substitute group

3,3-dimethyl

Naming the complete molecule

With four carbon atoms in the chain, name should be finished as butanoic acid. So final name is 3,3-dimethylbutanoic acid.

What is the iupac name ending for carboxylic acids?

All carboxylic acids' IUPAC names should be finished as 'oic acid'. As examples, ethanoic acid, benzoic acid can be shown. Note that, there should be a gap between oic and acid words.

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