{"id":368,"date":"2017-11-14T12:05:45","date_gmt":"2017-11-14T12:05:45","guid":{"rendered":"http:\/\/chemdictionary.org\/?p=368"},"modified":"2017-11-14T12:24:35","modified_gmt":"2017-11-14T12:24:35","slug":"carboxylic-acid","status":"publish","type":"post","link":"https:\/\/chemdictionary.org\/carboxylic-acid\/","title":{"rendered":"Carboxylic acid"},"content":{"rendered":"

Definition of carboxylic acid<\/h2>\n

Organic compounds containing carboxyl functional group (-COOH) are called carboxylic acid. The general formula of carboxylic acid is:<\/p>\n

\"By<\/p>\n

Carboxylic acid is composed of two functional groups carbonyl group (-CO-) and hydroxyl group(-OH). The name carboxyl derived from the first four letters of carbo<\/span>nyl and the last four letters of hydroxyl<\/span>.<\/p>\n

Classification<\/h2>\n

Depending on the number of carboxylic acid group present, it is classified as monocarboxylic acid, dicarboxylic acid, tricarboxylic acid or tetracarboxylic acid. An example of tetracarboxylic acid is given below:<\/p>\n

\"By
Ethylenetetracarboxylic acid<\/figcaption><\/figure>\n

Nomenclature<\/h2>\n

In IUPAC system the carboxylic acid is named as alkanoic acid. The suffix in alkane -e is replaced by -oic acid to give the name of the corresponding carboxylic acid. For example:<\/p>\n

HCOOH\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0Methanoic acid
\nCH2<\/sub>COOH\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Ethanoic acid
\nCH2<\/sub>CH2<\/sub>COOH\u00a0 \u00a0 \u00a0 \u00a0 Propanoic acid<\/p>\n

The compounds contain branch or substituents in different position, the longest carbon chain with carboxylic acid is selected and numbered started from the carbon contains carboxyl functional group (-COOH).<\/p>\n

For the small chain acids, common names are mostly used. There are no rules for these but end with -ic acid. For example:<\/p>\n

HCOOH\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0Formic acid
\nCH2<\/sub>COOH\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Acetic acid<\/p>\n

Physical properties<\/h2>\n

Boiling point<\/h3>\n

The boiling point of carboxylic acid increases with the increase of molecular weight. Boiling point of carboxylic acid is higher than the boiling point of alcohols with same or similar molecular weight. This is because of the formation of dimer between two acids by hydrogen bonding. Before the acid boils the hydrogen bonds in the dimer must be broken, thus the boiling point rises up.<\/p>\n

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Solubility<\/h3>\n

Lower chain carboxylic acids are soluble in water but higher chain carboxylic acids are insoluble. Carboxylic acid is polar compound. It has both hydrogen bond acceptor (the carbonyl -C=O<\/span> oxygen) and hydrogen bond donor (the hydrogen in -COOH<\/span> group). Thus they form hydrogen bond with water to become water soluble. But because of the hydrophobic nature of the aliphatic chain as the carbon chain increases, the solubility in decreases. For the same reason the higher chain acids are readily soluble in non polar or less polar solvent like ethanol, ether and benzene.<\/p>\n

Acidity<\/h3>\n

In aqueous solution, Carboxylic acid dissociates to give H+<\/sup>\u00a0cations and RCOO–<\/sup> anions. The negative charge on carboxylate anion is delocalized over the two oxygen and carbon atom. Thus it acts as a weak acid.<\/p>\n

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Preparation<\/h2>\n