Carboxylic Acid Properties

What is Carboxylic Acid?

Carboxylic Acid is an organic compound having a carboxyl functional group. They occur widely in nature, and also they are synthetically manufactured by humans. Carboxylic acids upon deprotonation yield a carboxylate anion with the general formula R-COO–, which can form a variety of useful salts like soaps.

Carboxylic acids are the most critical functional group that presents C=O. Different routes can obtain these organic compound types, some carboxylic acids, like lactic acid, citric acid, or fumaric acid, are produced from fermentation. Most of these carboxylic acids are applied in the food industry.

Carboxylic Acid Structure

The carboxylic acid structural formula is R-COOH. Where COOH refers to the carboxyl group, and R refers to the rest of the molecule in which this group is attached to. There exists a carbon in this carboxyl group that shares a single bond with a hydroxyl group and a double bond with an oxygen atom.

The general carboxylic acid structure is represented below.

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From the above representation, it is observed that a carboxylic acid having a hydroxyl group is attached to a carbonyl carbon. Because of the oxygen atom’s electronegativity, this functional group may undergo ionization and discharge a proton.

The carboxylate ion, produced from the removal of a carboxyl group’s protein is stabilized by the presence of two oxygen atoms (by which the negative charge can move). A few of the common examples of carboxylic acids are formic acid, and acetic acid (a component of vinegar).

Nomenclature of Carboxylic Acids

In general, these organic compounds are known by their trivial names, which contain the suffix “-ic acid.” For example, the trivial name for a carboxylic acid is acetic acid (CH3COOH). A suffix of “-oic acid” is assigned in the IUPAC nomenclature of these compounds.

The guidelines that are supposed to be followed in the IUPAC nomenclature of carboxylic acids are given below.

  • The “e” suffix in the corresponding alkane name is replaced with “oic acid.”

  • When the aliphatic chain contains only one carboxyl group, the carboxylic carbon is always numbered as one. As an example, CH3COOH is named as ethanoic acid.

  • When the aliphatic chain contains more than one carboxylic group, the total number of carbon atoms is counted, and the number of carboxylic groups is denoted by a Greek numeral prefixes as “tri-, “di-,” and likewise.

  • Naming a carboxylic acid is done by adding these suffixes and prefixes to the parent alkyl chain. The Arabic numerals are used to indicate the positions of the carboxyl group.

  • Also, the name “carboxy” or “carboxylic acid” can be assigned for a carboxyl substituent on a carbon chain. Such an example of nomenclature is, the name 2-carboxyfuran for 2-Furoic acid compound.

A few of the examples describing the nomenclature of carboxylic acids as per the IUPAC guidelines are tabulated below.

Examples of Carboxylic Acid

Trivial Name and Formula

IUPAC Name of the Carboxylic Acid

Formic acid, H - COOH

Methanoic acid

Crotonic acid, CH3CH=CH-COOH

But-2-enoic acid

Carbonic acid, OH-COOH

Carbonic acid

Butyric acid, CH3(CH2)2COOH

Butanoic acid

Carboxylic Acid Properties

Many of the carboxylic acid properties result in the presence of the carboxyl group. A few of such physical and chemical carboxylic acid properties are described below.

Physical Properties of Carboxylic Acids

  • Carboxylic acid molecules are polar because of the presence of two electronegative oxygen atoms.

  • Also, they participate in hydrogen bonding because of the presence of hydroxyl and carbonyl group (C=O).

  • These compounds form dimers when placed in nonpolar solvents via hydrogen bonding between the hydroxyl group of one carboxylic acid and to the other carbonyl group.

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  • The compounds solubility containing the carboxyl functional group in water depends on the size of the compound. The smaller the compound (, the shorter, the R group), the higher the solubility.

  • Generally, the boiling point of a carboxylic acid is higher than that of water.

  • These compounds have the ability to donate protons, and thus they are Bronsted-Lowry acids.

  • Generally, they have a strong sour smell. Their esters, however, have pleasant odors, and therefore they are used in perfumes.

Chemical Properties of Carboxylic Acids

  • The α-carbon belonging to a carboxylic acid can be easily halogenated via the Hell-Volhard-Zelinsky reaction.

  • Using the Schmidt reaction, these compounds can be converted into amines.

  • The carboxylic acid can be reduced to alcohol by treating a carboxylic acid with hydrogen to cause a hydrogenation reaction.

  • Upon alcohol reaction, these compounds yield esters.

Uses of Carboxylic Acids

On many available uses of carboxylic acids, a few of them are listed below.

  • The fatty acids that are essential to human beings are carboxylic acids. Carboxylic acid examples are omega-6 and omega-3 fatty acids.

  • Also, the higher fatty acids are used in soap manufacture.

  • The production of many food products and soft drinks involves the use of various carboxylic acids.

  • The rubber manufacture involves the use of acetic acid as a coagulant.

  • Hexanedioic acid is used for nylon manufacturing.

  • Carboxylic acids have numerous applications in the textile, rubber, and leather industries.

  • Ethylenediaminetetraacetic acid is a very commonly used chelating agent.

  • Many drug synthesis involves the use of these compounds. Carboxylic acids, therefore, are more important in pharmaceuticals.

  • The production of several polymers involves the use of carboxyl compounds contained in the functional group.

FAQ (Frequently Asked Questions)

1. What are Carboxylic Acids?

  • Carboxylic acids have a carboxyl functional group.

  • In organic chemistry, they are part of the homologous series.

  • On the esterification reactions, the hydrochloric from the carboxyl and hydrogen from alcohol are removed (condensation reaction in which a water molecule is removed to join the other two molecules, here, to create an Ester linkage/bond).

  • In the event of an esterification reaction, the conditions/reagents and catalysts are concentrated sulphuric acid and reflux, which is essentially supplying heat.

A few of the examples of Carboxylic acid groups are Carbonic Acid (OHCOOH), Formic Acid (HCOOH), Acetic Acid (CH3COOH), and many more.

2. How are Carboxylic Acids Identified?

The below tests can be used to identify carboxylic acids.

  1. Litmus Test

Carboxylic acid transforms blue litmus red. The hydroxyl group in carboxylic is far more acidic compared to the one in alcohol. The dissociation of the carboxylic acid is shown below.

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  1. Sodium Hydrogen Carbonate Test

Carboxylic acids undergo reaction with sodium hydrogen carbonate to produce carbon dioxide gas. This gas can be seen in the brisk effervescence form.

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  1. Ester Test

These acids also react with alcohol in the presence of concentrated sulphuric acid to form esters that are identified by the presence of a fruity smell.

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