Carboxyl group

Carboxyl group is a functional group consisting of a carbon atom double-bonded to an oxygen atom (C=O) and also bonded to a hydroxyl group (OH). It has the formula -COOH. This group is key in the structure of many organic molecules, including amino acids and fatty acids, and is characteristic of the carboxylic acids class of organic compounds.

Structure and Properties

The carboxyl group is polar due to the electronegativity difference between the oxygen and carbon atoms, making compounds containing this group soluble in water. The double bond between the carbon and oxygen is known as a carbonyl group, while the single bond to the hydroxyl group classifies it as an alcohol. When combined, these features give the carboxyl group its acidic properties, as the hydrogen atom in the hydroxyl part can dissociate as a proton (H+), leaving behind a negatively charged carboxylate ion (COO−).

Chemical Reactions

Carboxyl groups are involved in various chemical reactions, including:

• Esterification: Reacting with alcohols to form esters and water.
• Amide Formation: Reacting with amines to form amides.
• Decarboxylation: Losing a carbon dioxide molecule to form a hydrocarbon.
• Reduction: Being reduced to an alcohol by agents such as lithium aluminium hydride.

These reactions are fundamental in biochemical processes and industrial applications, including the synthesis of polymers, pharmaceuticals, and perfumes.

Biological Significance

In biology, the carboxyl group is essential for the structure and function of biomolecules. For example, it is a defining feature of amino acids, the building blocks of proteins. The carboxyl group of one amino acid can form a peptide bond with the amino group of another, creating the polymer chain of a protein. In fatty acids, the carboxyl group is involved in forming lipids through esterification, contributing to the structure of cell membranes and energy storage molecules.

Environmental Impact

Carboxylic acids, which contain the carboxyl group, are found in various natural and synthetic compounds. Some of these acids, such as acetic acid (vinegar), are benign, while others, like benzoic acid, are used as food preservatives. However, certain synthetic carboxylic acids can have environmental impacts, contributing to pollution and toxicity issues if not managed properly.

See Also

• Organic chemistry
• Functional group
• Acid-base reaction
• Polymer chemistry