Advanced Topic 789 of 1102 Organic Chemistry
E1 Elimination
A two-step elimination via carbocation giving alkenes.
In-depth explanation of E1 Elimination
E1 elimination is a two-step unimolecular elimination that begins with the same slow ionization as the SN1 reaction, forming a carbocation. In the fast second step, a base removes a proton from a carbon next to the cation, forming a new carbon-carbon double bond. Because the rate-determining step does not involve the base, the rate depends only on the substrate. E1 competes with SN1 and is favoured by heat, tertiary substrates and weakly basic conditions, and the more substituted alkene, the Zaitsev product, is usually the major product.
Going deeper: E1 Elimination
Key ideas: Unimolecular elimination through the same carbocation as SN1, then a base removes a beta proton to give an alkene. Rate depends on substrate only. Favoured by tertiary substrates, polar protic solvent, weak bases and heat; higher temperature favours elimination over substitution since entropy increases. The more substituted alkene (Zaitsev) dominates and rearrangement can occur.
Common mistakes and connections: Students think a strong base is needed; a strong base would give E2 instead. Another error is forgetting that E1 and SN1 give product mixtures. Alcohol dehydration with concentrated H2SO4 is E1 for secondary and tertiary alcohols. Links to carbocation rearrangement and the Zaitsev rule.
Visualization of E1 Elimination
E1 has a slow ionization to a carbocation intermediate, then a fast loss of H+ to the base gives the alkene. The interactive lesson shows this as a live animation or chart.
Worked example and use case
tert-Butyl chloride heated in ethanol gives isobutene, (CH3)2C=CH2, as the main elimination product.
Frequently asked questions about E1 Elimination
What is E1 Elimination?
A two-step elimination via carbocation giving alkenes.
Is E1 Elimination a beginner, intermediate or advanced topic?
E1 Elimination is a advanced topic in Organic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before E1 Elimination?
Study these earlier topics in Organic Chemistry first: Haloalkanes, SN1 Reaction, SN2 Reaction.
What comes after E1 Elimination?
The next topics in Organic Chemistry are E2 Elimination and Zaitsev's Rule.
Can I practise E1 Elimination with quizzes?
Yes. The interactive lesson includes a self-check question on E1 Elimination, and the Organic Chemistry quiz draws on every topic in this area.
Where E1 Elimination fits in Organic Chemistry
E1 Elimination is topic 61 of 148 in Organic Chemistry.