The carboxyl functional group that distinguishes carboxylic acids is uncommon in that it is composed of two functional groups that have already been discussed in this work. As seen in the formula on the right, the carboxyl group comprises a hydroxyl group that connects with a carbonyl group. It is commonly abbreviated as –CO2H or –COOH.

Carboxylic Acids

Chemical compounds with carboxyl functional groups connected to a hydrocarbon radical, sometimes known as organic acids, are carboxylic acids.  A considerable proportion of them may be found in nature, where they serve as intermediates in the breakdown of different compounds like amino acids, lipids, and carbohydrates.

Structure of Carboxylic Acid

A carbon (C) atom is linked to an oxygen (O) atom by a double bond, and a hydroxyl group (OH) is linked to carbon (C) by a single bond in a carboxylic acid, which belongs to the family of organic molecules called carboxylic acids. In addition, a fourth bond connects the carbon atom to a group of hydrocarbon molecules (R). Following the carbonyl group’s footsteps (C=O) and the hydroxyl group, the carboxyl (COOH) group was created.

The general formula of Carboxylic Acid

A carboxylic acid’s general formula is

 R-COOH,

where COOH signifies the carboxyl group and R specifies the remainder of the molecule to which this group is attached. A carbon atom in this carboxyl group forms a double connection with an oxygen atom and a single bond with a hydroxyl group.

The first four carboxylic acids generated from alkanes are

•     Methanoic acid (HCOOH),
•     Ethanoic acid (CH3COOH),
•     Propanoic acid (C2H5COOH)
•     Butanoic acid (C2H5COOH) (C3H7COOH).

Nomenclature of Carboxylic Acids

To name carboxylic acids, the simplest method is to count the number of carbons in the longest continuous chain that does not include the carboxyl carbon. The –e in the alkane or alkene name corresponding to the specified carbons is then substituted with the suffix –oic acid. The carboxylic acids listed in the table below are the most often encountered and are labeled with their systematic names.

Physical Properties

• Carboxylic acid molecules are polar because they include two electronegative oxygen atoms.
• Because the hydroxyl and carbonyl groups (C=O) in their structure also participate in hydrogen bonding.
• These compounds form dimers in nonpolar liquids due to hydrogen bonding between the hydroxyl groups of one carboxylic acid and the carbonyl groups of the other carboxylic acid.
• The solubility of compounds containing carboxyl functional groups in water is related to the size of the substance. The smaller the chemical, the greater its solubility (i.e., the shorter the R group).
• Carboxylic acid frequently has a higher boiling point than water.
• Because they may supply protons, they are known as Bronsted-Lowry acids.
• They generally have a strong sour odor. On the other hand, the esters offer pleasant scents that are used in perfumery.

Chemical Properties

●     Cleavage of O-H Bond

The acidity of Reactions Involving Cleavage of the O-H Bond (Reactions with Metals and Alkalis): Acidity of Reactions Involving Cleavage of the O-H Bond The dissociation of carboxylic acids in water results in the formation of resonance-stabilized carboxylate anions and the hydronium ion. We will go through a few more carboxylic acid examples.

●     Cleavage of C-OH Bond

Formation of Anhydride: Cleavage of the C-OH bond is involved in several reactions.

In the presence of mineral acids such as H2SO4 or P2O5, the formation of anhydride occurs.

Esterification: Esterification is the process by which carboxylic acids are esterified with alcohols or phenols by using a mineral acid as a catalyst, such as concentrated H2SO4 or HCl gas.

●     Cleavage of -COOH Group

Reduction: Reduction is a process of converting Carboxylic acid to alcohols with the assistance of lithium aluminum hydride, which is more efficient and effective than diborane in terms of efficiency and efficacy.

Decarboxylation: Decarboxylation occurs when carboxylic acids are heated with soda lime, causing the carbon dioxide present in them to be released and the creation of hydrocarbons to take place (NaOH and CaO in the ratio of 3: 1). Carboxylation is the chemical process that takes place.

Substitution Reactions

Halogenation: Halogenation is the process by which carboxylic acids are chlorinated or brominated in the presence of a trace amount of red phosphorus, resulting in the creation of halo carboxylic acids. These are carboxylic acids that include α-hydrogen in the α-position of the molecule. This reaction is referred to as the Hell-Volhard-Zelinsky response.

Ring Substitution: The ring structure of aromatic carboxylic acids happens when the carboxyl group serves as a deactivating and meta-directing group in the aromatic carboxylic acid. On the other hand, the Friedel-Crafts reaction does not occur in the presence of these chemicals.

Application of Carboxylic Acid

• Acyl halides are utilized to synthesize acid anhydrides, esters, and amides, amongst other things.
• Amides are widely utilized in the plastics, rubber, and paper industries, among other places. It is also employed in the treatment of water and sewage.
• A common practice to produce explosives, medicinal goods, industrial chemicals, and other items with acid anhydrides.
• Esters are employed in a variety of applications, including food flavoring, fragrances, cosmetics, and essential oils, among others, because of their pleasant odor.
• It is employed as an organic solvent in many applications.
• Surfactants are made from esters, which are employed in their production.
• In the treatment of leprosy and asthma, it is used extensively.
• In the food industry, ethanoic acid is produced using a solvent and vinegar.
• The chemical compound hexanedioic acid is used in the manufacture of nylon-6 and nylon-6-based composite products.
• Benzoic acid esters are commonly used in perfumery. It is also used as a food preservative, and its chemical name is sodium benzoate.
• Moe fatty acids are added to produce soap. Most bath and cleaning soaps contain sodium or potassium salts of fatty acids with higher molecular weights, such as stearic acid or palmitic acid.
• Several organic acids are used to produce soft drinks, food products, and other items in the food industry. Making vinegar is one example of how acetic acid is used. Organic acid sodium salts are utilized as preservatives in several applications.
• Organo-acids are used in various pharmaceutical medicines, including aspirin, phenacetin, and others.
• Rubber producers widely use acetic acids to avoid the creation of bubbles during the manufacturing process.

Conclusion

Carboxylic acid compounds may nevertheless find use in applications not discussed in detail in this section. From food to medication, from the human body to the earth and environment, the formation of these compounds and their destruction, absorption, or release significantly influence all the processes and reactions in these environments.