Amines: Revision and Reactions

Amines: Revision Notes

• Amines are nucleophilic and are basic in nature.
• They react with acids to form salts.
• Aliphatic amines are stronger bases than aromatic amines due to the +I effect.

Name Reactions

• Diazotization: Converts primary aromatic amines to diazonium salts.
• Hoffman Bromide Reaction: Converts amide to primary amine. Works for both aliphatic and aromatic compounds.
• Gabriel Phthalamide Synthesis: Used to prepare primary aliphatic amines.
• Coupling Reaction: Used for preparation of azo compounds.
• Carbylamine Reaction/Isocyanide Test: Differentiates primary amines from secondary and tertiary amines using chloroform and potassium hydroxide.

Preparations

• Reduction of Nitro Compounds: Converting nitro compounds into amines using hydrogen/palladium or tin/hydrochloric acid. Iron and hydrochloric acid is often preferred because the iron forms intermediate compounds that gets hydrolyzed to release ammonia.
• Ammonolysis of alkyl halides: Reaction of alkyl halides with ammonia to form amines.
• Reduction of Nitriles: Converting nitriles into amines using hydrogen/nickel, or sodium amalgam and alcohol. This is used to increase the carbon chain by one.
• Reduction of Amides: Converting amides into amines using lithium aluminum hydride.
• Gabriel Phthalamide Synthesis: Used to prepare aromatic 1° amines and avoid 2° and 3° amines.

Chemical Reactions

• Basic Character: Amines react with acids to form salts, which are soluble in water.

• Acylation: Reaction between amines and acylating agents to form amides or other derivatives.

• Diazotization Reactions: Chemical reactions in which primary aromatic amines are treated with nitrous acid (usually as sodium nitrite) and an acid. This produces stable diazonium salts, which are intermediates for the synthesis of a variety of products.

• Electrophilic Substitution Reactions: Amine groups can undergo aromatic electrophilic substitution reactions. These reactions involve replacing a hydrogen atom in the benzene ring with an electrophile. Bromination and nitration are often used for this purpose.

• Sulphonation: Addition of a sulphonic acid group (SO3H).

Tests

• Carbylamine Test: Used to distinguish primary amines from secondary and tertiary amines. Primary amines react to form isocyanides (carbylamines), which are foul-smelling.
• Reaction with Nitrous Acid: Used to distinguish primary and higher-order amines.
• Reaction with Aryl Sulphonyl Chloride: Used to differentiate among primary, secondary, and tertiary amines.

This quiz covers the essential concepts related to amines, including their nucleophilic nature and basicity. It also delves into key name reactions, preparation methods, and the distinctions between different types of amines. Test your knowledge on the chemistry of amines and their behaviors!