carboxyl group: meaning, definition, pronunciation and examples
C2Academic, Scientific, Technical
Quick answer
What does “carboxyl group” mean?
The univalent functional group –COOH, consisting of a carbonyl group bonded to a hydroxyl group. It is the defining functional group of carboxylic acids.
Audio
Pronunciation
Definition
Meaning and Definition
The univalent functional group –COOH, consisting of a carbonyl group bonded to a hydroxyl group. It is the defining functional group of carboxylic acids.
In biochemistry, the carboxyl group is a key component of amino acids (forming one end of the molecule) and fatty acids, and is central to many metabolic reactions, including the formation of peptide bonds and the regulation of pH via its proton-donating ability.
Dialectal Variation
British vs American Usage
Differences
No significant lexical differences. Minor potential variation in the pronunciation of 'carboxyl' (/kɑːˈbɒksɪl/ vs /kɑːrˈbɑːksɪl/). Spelling is identical.
Connotations
None; purely technical term.
Frequency
Equally frequent in academic and technical registers in both varieties.
Grammar
How to Use “carboxyl group” in a Sentence
The amino acid HAS a carboxyl group.The carboxyl group DONATES a proton.The reaction ACTIVATES the carboxyl group.The molecule TERMINATES in a carboxyl group.Vocabulary
Collocations
Examples
Examples of “carboxyl group” in a Sentence
noun
British English
- The carboxyl group is ionised at physiological pH.
- Modification of the carboxyl group can alter the drug's solubility.
American English
- The carboxyl group is ionized at physiological pH.
- The fatty acid has a long hydrocarbon chain attached to a carboxyl group.
Usage
Meaning in Context
Business
Virtually never used.
Academic
Core terminology in organic chemistry, biochemistry, and related life sciences. Used in textbooks, research papers, and lectures.
Everyday
Extremely rare outside educational or professional scientific contexts.
Technical
Fundamental term in chemical nomenclature, drug design, material science, and laboratory protocols.
Vocabulary
Synonyms of “carboxyl group”
Neutral
Weak
Vocabulary
Antonyms of “carboxyl group”
Watch out
Common Mistakes When Using “carboxyl group”
- Omitting 'group' and saying just 'carboxyl' when referring to the functional group (though technically 'carboxyl' can be a radical, 'carboxyl group' is the standard pedagogical term).
- Confusing 'carboxyl' with 'carbonyl' (C=O).
- Misspelling as 'carboxyle' or 'carboxy'.
FAQ
Frequently Asked Questions
No. A 'carboxyl group' is the functional group (–COOH). A 'carboxylic acid' is an entire organic compound that contains one or more carboxyl groups (e.g., acetic acid CH₃COOH).
The carbonyl carbon (C=O) pulls electron density away from the O–H bond in the hydroxyl part. This weakens the O–H bond, making it easier for the hydrogen ion (H⁺) to dissociate, which defines acidity.
In the IUPAC system, the presence of a carboxyl group typically gives the compound the suffix '-oic acid'. The carbon of the carboxyl group is carbon number 1 in the parent chain. Example: CH₃CH₂COOH is propanoic acid.
It is the conjugate base form of a carboxyl group, resulting from the loss of a proton (H⁺). It has the structure –COO⁻ and carries a negative charge. Salts of carboxylic acids contain carboxylate ions.
The univalent functional group –COOH, consisting of a carbonyl group bonded to a hydroxyl group. It is the defining functional group of carboxylic acids.
Carboxyl group is usually academic, scientific, technical in register.
Carboxyl group: in British English it is pronounced /kɑːˈbɒksɪl ɡruːp/, and in American English it is pronounced /kɑːrˈbɑːksɪl ɡruːp/. Tap the audio buttons above to hear it.
Learning
Memory Aids
Mnemonic
Imagine CARBO(nyl) + XY(l) from 'hydroxyl' having a lunch date. The Carbonyl (C=O) and the Hydroxyl (OH) group together form the CARBOXYL family.
Conceptual Metaphor
A 'functional handle': The carboxyl group is a site on a molecule where specific chemical 'handshakes' (reactions) can occur, particularly those involving acidity or bond formation.
Practice
Quiz
What is the primary chemical characteristic of a free carboxyl group in an aqueous solution at neutral pH?