Carboxylic acids
Alkanoic acids
Carboxylic acids, also known as alkanoic acids, all contain the carboxyl functional group 鈥揅OOH. Their names all end in '鈥oic acid'. Carboxylic acids can be represented by the general formula \({C_n}{H_{2n + 1}}COOH\).
When naming carboxylic acids, the position of the carboxyl group does not need to be identified with a number, as it is always found at the end of the carbon chain, and so is on the first carbon.
The smallest carboxylic acids are miscible in water:
- Methanoic
- Ethanoic
- Propanoic
- Butanoic
The larger a carboxylic acid gets, the lower the miscibility. The melting and boiling points of carboxylic acids increase with size due stronger intermolecular forces.
One of the most widely used carboxylic acids is vinegar. Also known as ethanoic acid, it has far more uses than simply being added to chips, and is commonly used in chemicals used to treat limescale in bathrooms or inside kettles. Many foods are also preserved in vinegar (pickled) to make them last for longer periods of time.
Lots of other carboxylic acids have less pleasant smells than vinegar and some are highly corrosive so must be handled with care. Like mineral acids, carboxylic acids have a pH less than 7 and form salts on neutralization with bases.
Salts
The following salts are made using carboxylic acids:
- Sodium hydroxide \(+\) ethanoic acid \(\rightarrow\) sodium ethanoate \(+\) water
- Lithium carbonate \(+\) propanoic acid \(\rightarrow\) lithium propanoate \(+\) water \(+\) carbon dioxide
- Magnesium \(+\) methanoic acid \(\rightarrow\) magnesium methanoate \(+\) hydrogen
- Calcium oxide \(+\) butanoic acid \(\rightarrow\) calcium butanoate \(+\) water
Alcohols that are oxidized create carboxylic acids