Alkenes & Alkynes
Competitive‑exam (IIT‑JEE Main & Advanced) – Chemistry
Goal: Master the structure, nomenclature, synthesis, reactivity, and key mechanisms of alkenes and alkynes.
Strategy:
- Conceptual clarity – why reactions happen.
- Mechanistic depth – step‑by‑step electron flow.
- Pattern recognition – Markovnikov vs anti‑Markovnikov, regio‑/stereo‑selectivity.
- Problem‑solving – practice with hard, multi‑step questions.
1. General Features
| Feature | Alkenes (C=C) | Alkynes (C≡C) |
|---|---|---|
| Hybridisation | sp² at each C | sp at each C |
| Bond angles | ~120° | ~180° |
| General formula | CₙH₂ₙ | CₙH₂ₙ₋₂ |
| π‑bond strength | 265 kJ mol⁻¹ | 260 kJ mol⁻¹ |
| Reactivity | More reactive than alkanes | Even more reactive (more π‑electron density) |
| Stability order (alkenes) | 1‑alkene < 2‑ |