Haloalkanes and Haloarenes
Free NCERT-aligned study resource for the 2026–27 academic session.
CBSE weightage: 6 marks. This unit is part of the official 70-mark Chemistry theory course for 2026–27. citeturn0search11
1. What You Need to Learn
Nature of C–X bond; preparation; physical and chemical properties; substitution mechanisms; haloarenes; polyhalogen compounds.
2. Core Concepts & Formulae
SN1 reactions proceed through a carbocation and generally favour tertiary substrates; SN2 reactions involve backside attack and are favoured by less hindered substrates. Haloarenes are less reactive toward nucleophilic substitution because of resonance and partial double-bond character of the C–X bond.
3. Common Mistakes
Keep reaction conditions with the mechanism: substrate, nucleophile, solvent and temperature can change the pathway. Distinguish substitution from elimination and explain why aryl halides behave differently from alkyl halides.
4. Exam-Focused Practice
- Predict SN1 or SN2 products for given substrates.
- Compare reactivity of primary, secondary and tertiary haloalkanes.
- Explain why chlorobenzene is less reactive than chloroethane toward nucleophilic substitution.
5. Quick Revision Checklist
- Can you define the key terms without looking at the book?
- Can you explain the main trend/reaction/mechanism with a reason?
- Can you solve a numerical or predict a product independently?
- Can you answer an application or competency-based question?