Carboxylic acids are organic compounds that have the carbonyl functional group, that is, a carbon that forms a double bond with another carbon and a single bond with an OH group.
The term “carboxylic acid” is used to designate an oxygenated organic function, that is, one that has an oxygen atom in its structure. The compounds belonging to this group have corrosive capacity and a sour taste, since they are acidic.
Carboxylic acids are a class of organic compounds that contain a carboxyl group (-COOH) as their functional group. Here are some key informations of carboxylic acids:
- Structure: Carboxylic acids consist of a carbon atom that is double-bonded to an oxygen atom (carbonyl group) and single-bonded to a hydroxyl group (-OH). The general formula for carboxylic acids is RCOOH, where R represents a hydrocarbon group.
- Acidity: Carboxylic acids are weak acids, meaning they can donate a hydrogen ion (H+) in solution. The presence of the carboxyl group makes the hydrogen in the -OH group more acidic compared to alcohols. The acidity of carboxylic acids allows them to undergo reactions with bases to form salts called carboxylates.
- Physical properties: Carboxylic acids are usually colorless liquids or solids at room temperature. They have distinct odors and are often responsible for the sour smell of certain fruits and vinegar. Carboxylic acids have higher boiling points compared to similar-sized alcohols and aldehydes due to the presence of intermolecular hydrogen bonding.
- Occurrence: Carboxylic acids are found in various natural sources, including fruits, vegetables, and animal fats. Examples include acetic acid (vinegar), citric acid (lemons), and butyric acid (butter).
- Reactions: Carboxylic acids can undergo a variety of reactions, including esterification, oxidation, and decarboxylation. Esterification involves the reaction of a carboxylic acid with an alcohol to form an ester. Oxidation of primary alcohols or aldehydes can yield carboxylic acids. Decarboxylation refers to the removal of a carboxyl group from a compound, often resulting in the formation of carbon dioxide and a smaller molecule.
Understanding carboxylic acids is important in various fields, including organic chemistry, biochemistry, and pharmaceuticals. They play essential roles in biological processes and have practical applications in industries such as food, medicine, and manufacturing.
Characteristics
- 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, except for acids that have one or two carbon atoms.
- Carboxylic acids that have up to nine carbons are liquid at room temperature.
- In solid state they are whitish and waxy in appearance.
- In liquid state they are colorless.
- As they have the carboxyl or carbonyl group, they can establish hydrogen bonding.
- Its compounds are polar.
- They are generally odorless, except for acids with up to three carbons, which have an irritating odor, and those with up to six carbons, which have a repugnant odor.
Examples
Carboxylic acid with six carbon atoms
This acid has a chain with six carbon atoms (prefix hex), it also has simple bonds (infix an) and a carbonyl (oic), therefore its name is hexanoic acid.
Carboxylic acid with six carbon atoms and branches
As this acid is branched, the main chain is the one with the greatest number of carbons and the carbonyl. In this compound, the main chain has five carbon atoms (pent prefix), only simple bonds between the carbon atoms (an infix) and a carboxyl (oic), which is why its name is 3-methylpentanioco acid.
NOTE: The numbering of the main chain should always start from the carbon of the carbonyl group.
Carboxylic acid with two carbonyls
This acid has a chain with four carbon atoms (prefix but), only simple bonds between the carbon atoms (infix an) and two carboxyls (dioic), therefore its name is butanedioic acid.
NOTE: Between the infix and the “dioecious” a vowel was added to unite them.
Applications
- Production of organic esters.
- Production of carboxylic acid salts.
- Preparation of perfumes.
- Vinegar production.
- Manufacture of artificial silks.
- Preparation of disinfectants.
- Fabric dyeing.