Chem

CARBOXYLIC ACIDS

Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group.[1] The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group.

A carboxyl group (or carboxy) is a functional group consisting of a carbonyl and a hydroxyl, which has the formula -C(=O)OH, usually written as -COOH or -CO2H.

Carboxylic acids are Brønsted-Lowry acids, they are proton donors. They are the most common type of organic acid. Among the simplest examples are the formic acid H-COOH, that occurs in ants, and acetic acid H3C-COOH group, that gives vinegar its sour taste. Acids with two or more carboxyl groups are called dicarboxylic, tricarboxylic, etc. The simplest dicarboxylic example is oxalic acid (COOH)2, which is just two connected carboxyls. Mellitic acid is an example of a hexacarboxylic acid. Other important natural examples are citric acid (in lemons) and tartaric acid (in tamarinds).

Salts and esters of carboxylic acids are called carboxylates. When a carboxyl group is deprotonated, its conjugate base, a carboxylate anion is formed. Carboxylate ions are resonance stabilized and this increased stability make carboxylic acids more acidic than alcohols.

The most widely practiced reactions convert carboxylic acids into esters, amides, carboxylate salts, acid chlorides, and alcohols. Carboxylic acids react with bases to form carboxylate salts, in which the hydrogen of the hydroxyl (-OH) group is replaced with a metal cation. Thus, acetic acid found in vinegar reacts with sodium bicarbonate (baking soda) to form sodium acetate, carbon dioxide, and water:

CH3COOH + NaHCO3 → CH3COO−Na+ + CO2 + H2O

Carboxylic acids also react with alcohols to give esters. This process is heavily used in the production of polyesters. Similarly carboxylic acids are converted into amides, but this conversion typically does not occur by direct reaction of the carboxylic acid and the amine. Instead esters are typical...