Carboxylic Acid
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What is the carboxylic acid functional group?
A carboxylic acid can be thought of as a combination between two functional groups: an alcohol group, involving a hydrogen bound to an oxygen, which attaches to a carbonyl group, involving a carbon double bound to an oxygen. Often, chemists abbreviate carboxylic acid to COOH group in chemical literature.
Reactions using a Carboxylic Acid Group
Carboxylic acids have remarkable versatility, and convert into many different functional groups, making them very useful in chemical synthesis. Let’s look at some of the most useful reactions.
Carboxylic acids convert into acid halides using thionyl chloride or phosphorus halides, like phosphorus tribromide or phosphorus pentachloride.
Carboxylic Acid Groups in Amino Acids
Biomolecules frequently have at least one carboxylic acid functional group. For instance, many amino acids have a carboxylic acid group as a fundamental part of the “amino acid backbone.”
These carboxylic acid groups form peptide bonds with amino acid amine groups, linking amino acids together, which provides the structural basis for all proteins. Peptide bond formation is a type of condensationreaction, involving the joining of two molecules which creates a water molecule as a byproduct. This carbonyl group bonded to a nitrogen is called an amide, and is found in many molecules outside of proteins.