AQA AS Chemistry: Nucleophilic Substitution

This is a complete lesson for AQA A-level Chemistry 3.3.3 Halogenoalkanes, focused on nucleophilic substitution with OH⁻ and CN⁻.

The lesson is designed to help students understand why halogenoalkanes undergo nucleophilic substitution, how to draw curly arrow mechanisms, and how to predict the products formed when halogenoalkanes react with aqueous hydroxide ions or ethanolic cyanide ions.

Students are guided through the key ideas step by step, including C-X bond polarity, nucleophile definition, leaving groups, reaction conditions, product formation and carbon chain extension using CN⁻.

Students will learn to:

• define halogenoalkane, nucleophile and nucleophilic substitution
• explain why the C-X bond is polar
• explain why the δ⁺ carbon is attacked by nucleophiles
• state the conditions for hydrolysis using aqueous NaOH or KOH
• state the conditions for nitrile formation using KCN in ethanol
• predict alcohol and nitrile products
• explain why CN⁻ is useful in organic synthesis
• draw curly arrow mechanisms for OH⁻ and CN⁻ substitution
• identify nucleophiles and leaving groups