Amines — A-Level Chemistry Revision

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What is Amines?

Amines are organic derivatives of ammonia where one or more hydrogen atoms have been replaced by alkyl or aryl groups. They are characterised by the lone pair of electrons on the nitrogen atom, which allows them to act as bases (accepting protons) and as nucleophiles (donating the electron pair). Primary, secondary, and tertiary amines are formed depending on the number of alkyl groups attached to the nitrogen.

Board notes: All boards cover the basicity and nucleophilicity of amines. AQA often includes questions on the preparation of amines from haloalkanes and the subsequent reactions to form more substituted amines. Edexcel places emphasis on the relative base strengths of ammonia, primary, secondary, and aromatic amines. OCR frequently tests the synthesis of azo dyes from phenylamine and diazonium salts.

Worked example

Common mistakes

• 1Confusing the classification of amines with that of alcohols. A primary amine has one alkyl group attached to the nitrogen (RNH2), whereas a primary alcohol has the -OH group on a carbon attached to only one other carbon.
• 2Assuming that all amines have the same base strength. The base strength of amines depends on the availability of the lone pair on the nitrogen. Alkyl groups are electron-donating and increase base strength, making secondary alkylamines the strongest bases.
• 3Incorrectly naming amines, particularly aromatic amines like phenylamine, which is the correct IUPAC name for aniline.

Amines exam questions

Exam-style questions for Amines with mark-scheme style solutions and timing practice. Aligned to AQA, Edexcel and OCR specifications.

Frequently asked questions

• How are amines prepared?

  Amines can be prepared by the nucleophilic substitution of a haloalkane with excess ethanolic ammonia. They can also be formed by the reduction of nitriles using a strong reducing agent like LiAlH4 or by catalytic hydrogenation.

• What are aromatic amines used for?

  Aromatic amines, such as phenylamine, are important intermediates in the synthesis of other organic compounds, particularly in the manufacture of azo dyes, which are used widely as colourants in food, textiles, and paints.