A Level
A-Level Chemistry: Organic Mechanisms: SN1 vs SN2, E1 vs E2
•By Intuitional Team•1 min read
A-Level Chemistry — Organic Mechanisms: SN1 vs SN2, E1 vs E2: quick notes, common traps, and an exam-style example.
SN1 mechanism
Two-step: first, leaving group departs → carbocation; then nucleophile attacks. Rate depends only on [substrate]. Favoured by tertiary halogenoalkanes, polar protic solvents.
SN2 mechanism
One-step: nucleophile attacks as leaving group leaves. Rate depends on [substrate][nucleophile]. Favoured by primary halogenoalkanes, strong nucleophiles, polar aprotic solvents.
Exam habits
- Draw curly arrows clearly.
- Note inversion of configuration for SN2 (Walden inversion).
- For SN1, mention racemisation if chiral centre forms.
Tags
A-LevelChemistryOrganic Mechanisms