Carboxylic Acids
Preparation, acidic strength and the effect of substituents; important reactions. (Chemistry › Aldehydes, Ketones and Carboxylic Acids, NEET UG syllabus.)
What is Carboxylic Acids?
An organic compound containing a carboxyl functional group (-COOH).
Key formula / rule: General Carboxylic Acid
Key points
- Identify and name carboxylic acids and their derivatives.
- Describe various methods for the preparation of carboxylic acids.
- Explain the acidic nature of carboxylic acids and the factors affecting their acidic strength.
- Predict the products of important reactions of carboxylic acids, including esterification, reduction, decarboxylation, and HVZ reaction.
Common exam trap
Confusing the reactivity of LiAlH₄ and NaBH₄ with carboxylic acids.
Definitions
- Term
Carboxylic Acid
- Meaning
An organic compound containing a carboxyl functional group (-COOH).
- Term
Carboxylate Anion
- Meaning
The resonance-stabilized anion (R-COO⁻) formed when a carboxylic acid loses a proton.
- Term
Decarboxylation
- Meaning
A chemical reaction that involves the removal of a carboxyl group (-COOH) as carbon dioxide (CO₂).
- Term
Fischer Esterification
- Meaning
The acid-catalyzed reaction between a carboxylic acid and an alcohol to form an ester and water.
- Term
Hell-Volhard-Zelinsky (HVZ) Reaction
- Meaning
A reaction used for the α-halogenation of carboxylic acids containing an α-hydrogen, using halogen (Cl₂ or Br₂) in the presence of red phosphorus.
Learning objectives
Identify and name carboxylic acids and their derivatives.
Describe various methods for the preparation of carboxylic acids.
Explain the acidic nature of carboxylic acids and the factors affecting their acidic strength.
Predict the products of important reactions of carboxylic acids, including esterification, reduction, decarboxylation, and HVZ reaction.
Understand the electrophilic substitution reactions of aromatic carboxylic acids.
Formulae
- Name
General Carboxylic Acid
- Note
R represents an alkyl or aryl group.
- Expression
R-COOH
- Name
Carboxylate Anion
- Note
Resonance stabilized conjugate base.
- Expression
R-COO⁻
- Name
Fischer Esterification
- Note
Acid-catalyzed reaction to form an ester.
- Expression
R-COOH + R'-OH ⇌ R-COOR' + H₂O
- Name
Decarboxylation
- Note
Removal of CO₂ from the carboxyl group.
- Expression
R-COOH + NaOH/CaO (heat) → R-H + Na₂CO₃
- Name
Hell-Volhard-Zelinsky (HVZ) Reaction
- Note
Halogenation at the α-carbon (requires α-hydrogen).
- Expression
R-CH₂-COOH + X₂ (Red P) → R-CH(X)-COOH
Prerequisites
Basic organic nomenclature and functional groups.
Understanding of inductive and resonance effects.
Knowledge of oxidation and reduction reactions in organic chemistry.
Concepts of nucleophilic acyl substitution.
Grignard reagents and their reactions.
Common mistakes
Confusing the reactivity of LiAlH₄ and NaBH₄ with carboxylic acids.
Incorrectly predicting the effect of substituents (EWG/EDG) on acidic strength.
Forgetting that the carboxyl group is meta-directing and deactivating in electrophilic aromatic substitution.
Not recognizing the conditions for decarboxylation (soda lime + heat).
Overlooking the requirement of an α-hydrogen for the HVZ reaction.
Keywords
Carboxylic acid
Carboxyl group
Acidic strength
Carboxylate anion
Esterification
Decarboxylation
HVZ reaction
Electron-withdrawing group
Electron-donating group
Grignard reagent
LiAlH₄
Soda lime
Practice preview
Which of the following reagents can convert a nitrile into a carboxylic acid?…
easy
The reaction of a carboxylic acid with an alcohol in the presence of a concentrated acid catalyst is known as:…
easy
What is the final product (Z) in the following reaction sequence? CH3Br --(Mg, dry ether)--> X --(CO2, then H3O+)--> Y --(PCl5)--> Z…
medium