Carboxylic Acids

01Carboxylic Acids

Structure and nomenclature

This section covers the carboxyl functional group, the structure of carboxylic acids and the rules used to name them.

The carboxyl group

Carboxylic acid: an organic compound containing the carboxyl functional group, $\ce{-COOH}$ . Carboxylic acids can be represented generally as $\ce{RCOOH}$ .

The general formula may also be written as $C_nH_{2n+1}COOH$ .

Propanoic acid

Formula: $\ce{CH3CH2COOH}$

Ethanedioic acid

Formula: $\ce{HOOC-COOH}$

Naming carboxylic acids

Names of carboxylic acids use the ending -oic acid. The carbon atom in the $\ce{-COOH}$ group is carbon 1, so a position number is not needed for the acid group.

Number the carbon chain from the carboxylic-acid end.
Examples include methanoic acid, ethanoic acid and propanoic acid.
When carboxyl groups occur at both ends of the chain, use the ending -dioic acid, as in ethanedioic acid.

Formula	Name
$\ce{HCOOH}$	methanoic acid
$\ce{CH3COOH}$	ethanoic acid
$\ce{CH3CH2COOH}$	propanoic acid
$\ce{HOOC-COOH}$	ethanedioic acid

02Carboxylic Acids

Weak acid behaviour

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Partial ionisation

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\ce{RCOOH(aq) <=> RCOO^-(aq) + H^+(aq)}

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Example: ethanoic acid

\ce{CH3COOH(aq) <=> CH3COO^-(aq) + H^+(aq)}

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03Carboxylic Acids

Reactions with carbonates

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Products of the reaction

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\ce{2RCOOH + Na2CO3 -> 2RCOONa + H2O + CO2}

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Ionic equation

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\ce{2RCOOH + CO3^2- -> 2RCOO^- + H2O + CO2}

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$\ce{2CH3COOH + Na2CO3 -> 2CH3COONa + H2O + CO2}$

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