Carboxylic Acids and Derivatives

Topic Overview

This topic focuses on recognising functional groups, understanding their preparation, learning their reactions and conditions, and applying the ideas to organic synthesis, polymers, and industrial uses.

Carboxylic acids Esters Acyl chlorides Amides Acid anhydrides Nitriles

1. Carboxylic Acids

Identify the carboxyl functional group: -COOH.
Know that carboxylic acids are weak acids.
Understand that they react with carbonates to release CO₂.
Explain their boiling points and solubility in terms of hydrogen bonding.
Prepare carboxylic acids by oxidation of alcohols or aldehydes.
In some specifications, prepare them by hydrolysis of nitriles.

2. Esters

Esterification:
carboxylic acid + alcohol → ester + water
Condition: acid catalyst

Identify the ester functional group: -COO-.
Know that esters are formed from carboxylic acids and alcohols.
Learn the hydrolysis of esters in acidic and alkaline conditions.
Know common uses of esters in perfumes, flavourings, solvents, and plasticisers.
Understand links to fats and oils, soap formation, and biodiesel.

3. Acyl Chlorides and Acylation

Identify the acyl chloride functional group.
In OCR, acyl chlorides are prepared from carboxylic acids using SOCl₂.
Study reactions of acyl chlorides with:

Water
forms carboxylic acids

Alcohols
forms esters

Ammonia
forms amides

Amines
forms substituted amides

AQA explicitly requires the nucleophilic addition–elimination mechanism for reactions of acyl chlorides with water, alcohols, ammonia, and primary amines.

4. Amides

Know the structure of primary and secondary amides.
Understand that amides can be prepared from acyl chlorides.
Know that polyamides are formed by condensation polymerisation.

5. Acid Anhydrides

Some specifications, especially AQA, include the structure of acid anhydrides.
They undergo nucleophilic addition–elimination reactions similar to acyl chlorides.
They react with water, alcohols, ammonia, and amines.
An industrial example is the use of ethanoic anhydride in aspirin manufacture.

6. Nitriles

Nitriles are important for carbon-chain extension in organic synthesis.
They can be formed by reaction of haloalkanes with CN⁻ in ethanol.
This reaction uses the nucleophilic substitution mechanism.
Nitriles can also be linked to reactions of carbonyl compounds with HCN.
Hydrolysis of nitriles can produce carboxylic acids.

7. What to Revise

Area	What to know
Functional groups	Structures and names of carboxylic acids, esters, acyl chlorides, amides, acid anhydrides, nitriles
Preparations	Oxidation routes, esterification, hydrolysis of nitriles, formation of acyl chlorides using SOCl₂
Reactions	Acid reactions, ester hydrolysis, acyl chloride reactions, amide formation
Mechanisms	Nucleophilic substitution, nucleophilic addition, nucleophilic addition–elimination
Applications	Soap, biodiesel, polymers, perfumes, flavourings, aspirin manufacture

Summary

In short, this A-Level topic is about recognising the functional groups, learning how they are made, understanding their reactions and mechanisms, and applying them in organic synthesis and industry.