How do I revise Alkenes for A-Level?

Use MasteryMind's Alkenes revision notes alongside practice questions and past papers. Focus on key definitions, worked examples, and exam-style questions to build confidence for your AQA A-Level exam.

Is this Alkenes guide aligned to the AQA specification?

Yes. This revision guide is specifically written for the AQA A-Level specification and covers all required content for Alkenes.

Alkenes Revision Notes — AQA A-Level

Alkenes are unsaturated hydrocarbons that contain a carbon-carbon double bond, making them highly reactive and essential for creating everyday plastics. Mastering this topic is crucial for the exam, as it bridges organic mechanisms with real-world polymer applications.

Overview

Alkenes are a vital family of unsaturated hydrocarbons, characterised by the presence of at least one carbon-carbon double bond (C=C). This double bond is the defining feature of alkenes, acting as a centre of high electron density that makes them significantly more reactive than alkanes. In GCSE Chemistry, understanding alkenes is essential because they form the basis of electrophilic addition reactions and are the fundamental building blocks for addition polymers like poly(ethene) and PVC.

Examiners frequently test your ability to draw reaction mechanisms with precise curly arrows, explain the stability of carbocation intermediates to predict major products, and draw repeating units of polymers. This topic connects strongly with crude oil fractions, environmental chemistry (disposal of plastics), and structural isomerism.

Key Concepts

Concept 1: The Carbon-Carbon Double Bond

The defining feature of an alkene is the C=C double bond. This consists of a standard strong covalent bond (a sigma bond) and a weaker secondary bond (a pi bond) that sits above and below the plane of the atoms. The pi bond represents a region of high electron density. Because it is electron-rich, it strongly attracts electrophiles (electron-deficient species). This is why alkenes undergo electrophilic addition reactions, whereas alkanes generally undergo substitution reactions.