What are carboxylic acids?

What are carboxylic acids? These are compounds that have carboxyl as a functional group and have several industrial and laboratory applications.

Carboxylic acids are organic compounds that have the carboxyl functional group, that is, a carbon that performs a double bond with oxygen and a simple bond with an OH group.

Carboxyl is the functional group of all carboxylic acid

The term carboxylic acid is used to designate an oxygenated organic function, that is, it has an oxygen atom in its structure. The compounds belonging to this group have a corrosive capacity and a sour taste, as they are acidic.

Characteristics of carboxylic acids

  • In general, they are soluble in organic solvents;
  • The only carboxylic acids that are soluble in water are those that have up to four carbon atoms in their structure;
  • In general, carboxylic acids are denser than water, with the exception of acids with one or two carbon atoms;
  • Carboxylic acids with up to nine carbons are liquid at room temperature;
  • In the solid state, they are whitish and have a waxy appearance (of wax);
  • In the liquid state, they are colorless;
  • Since they have carboxyl, they are capable of establishing hydrogen bonds ;
  • Its compounds are polar;
  • In general, they are odorless, with the exception of acids with up to three carbons, which have an irritating smell, and those with up to six carbons, which have a disgusting smell;


The two best known carboxylic acids are metanoic acid and ethanoic acid.

Metanoic acid

Metanoic acid or formic acid received this name for being extracted for the first time from the distillation of ants. The acid is injected by the red ants and cause itching and swelling at the sting.

It is a colorless, liquid and strong-smelling acid.

Metanoic acid can be obtained from the reaction of carbon monoxide and caustic soda.

A characteristic that differentiates them from other carboxylic acids is the presence of the aldehyde functional group. With this, it can be easily oxidized, releasing carbon dioxide and water.

See also: Exercises on Organic Chemistry with template

Etanoic acid

The ethanoic acid or acetic acid is the main component of vinegar.

It is a colorless liquid, with a strong smell and a sour taste.

In addition to food use, acetic acid is also used in industries to produce substances that make up paints, solvents and dyes.

See also: Exercises on Organic Functions

Carboxylic acid salts

Carboxylic acid reacts with bases , producing salts of carboxylic acids and water. The name of this reaction is salification .

In the presence of water, these salts undergo hydrolysis and can regenerate the carboxylic acid and the base that gave rise to them.

Carboxylic acid salts are used to make soaps.

Some important carboxylic acids

Metanoic acid (formic acid): it was obtained for the first time by macerating ants (hence the formic name). It is a colorless liquid, with an irritating smell and that causes irritation in tissues and mucous membranes. It is used industrially as a fixer for dyes and pigments in cotton and wool fabrics.

Etanoic acid (acetic acid): it is a colorless liquid, irritating smell and sour taste, formed through the oxidation of ethanol and used in food in the form of vinegar. It can also be used as a precursor as a cleaning product, and in the preparation of perfumes, dyes, artificial silk and acetone .

Benzoic acid : it is found naturally in some plants and its salts are used as a fungicide and food preservative. It is a white, crystalline solid, soluble in water.

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