acid halide
C2Technical / Scientific
Definition
Meaning
An organic compound formed by replacing the hydroxyl group of a carboxylic acid with a halogen atom.
Any of a class of chemical compounds derived from an oxoacid by replacing a hydroxyl group with a halide group (e.g., acyl halides like acetyl chloride); reactive intermediates in organic synthesis.
Linguistics
Semantic Notes
Also known as 'acyl halides', though 'acid halide' is a broader term that can also include derivatives of inorganic oxoacids. They are characterized by high reactivity, especially with nucleophiles.
Dialectal Variation
British vs American Usage
Differences
No significant difference in meaning or usage. Both use the term identically in scientific contexts.
Connotations
Neutral, purely technical.
Frequency
Term is used equally in UK and US chemistry publications and education.
Vocabulary
Collocations
Grammar
Valency Patterns
Noun + of (e.g., 'acid halide of acetic acid')Adjective + acid halide (e.g., 'reactive acid halide')Vocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Phrases
Idioms & Phrases
- “Fuming like an acid halide (informal, lab jargon for a volatile, reactive substance).”
Usage
Context Usage
Business
Not used.
Academic
Used in chemistry textbooks, research papers, and lectures on organic synthesis.
Everyday
Not used.
Technical
Core term in organic chemistry labs, chemical industry (pharmaceuticals, polymer production).
Examples
By Part of Speech
verb
British English
- The carboxylic acid was *halogenated* to form the corresponding acid halide.
American English
- They *converted* the acid to an acid halide using thionyl chloride.
adverb
British English
- The compound reacted *acid-halide-like* with the amine.
American English
- It behaves *like an acid halide* in the presence of water.
adjective
British English
- The *acid halide* intermediate was too unstable to isolate.
American English
- This *acyl halide* functionality is key to the reaction.
Examples
By CEFR Level
- Acid halides are important for making other organic compounds.
- Acetyl chloride is a common acid halide.
- The acid halide, synthesized via reaction with phosphorus pentachloride, underwent immediate aminolysis to yield the desired amide.
- Due to their electrophilicity, acid halides are far more reactive than their parent carboxylic acids.
Learning
Memory Aids
Mnemonic
ACID Halide: A Carboxylic acid's -OH Is Displaced by a Halide.
Conceptual Metaphor
A 'chemical weapon' in synthesis—highly reactive and used to attack other molecules to build new structures.
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Avoid literal translation as 'кислотный галогенид' in non-scientific contexts—it will be meaningless. The established Russian term is 'галогенангидрид кислоты' or 'ацилгалогенид'.
Common Mistakes
- Using 'acid halide' to refer to simple metal halides like sodium chloride. Incorrect: 'Table salt is an acid halide.'
- Confusing 'acid halide' with 'alkyl halide' (where halogen is attached to a carbon chain, not a carbonyl group).
Practice
Quiz
What is the core structural feature of an acid halide?
FAQ
Frequently Asked Questions
In organic chemistry, particularly for carboxylic acids, they are often used synonymously. 'Acyl halide' is more precise for derivatives of carboxylic acids, while 'acid halide' can be a broader term including inorganic acids.
The halogen atom is a good leaving group, and the carbonyl carbon is highly electrophilic due to the electron-withdrawing effect of the halogen and the carbonyl oxygen, making it susceptible to nucleophilic attack.
Generally no. They are highly reactive with water (hydrolyze) and are typically synthetic intermediates, not stable natural products.
Acid chlorides (acyl chlorides), such as acetyl chloride, are the most common due to the availability and effectiveness of chlorinating agents like thionyl chloride.