Advanced Topic 787 of 1102 Organic Chemistry
SN1 Reaction
A two-step unimolecular nucleophilic substitution through a carbocation, favoring tertiary substrates.
In-depth explanation of SN1 Reaction
The SN1 reaction is a two-step unimolecular nucleophilic substitution in which the rate depends only on the substrate, so the rate law is rate equal to k times the concentration of the haloalkane. In the slow first step the leaving group departs to form a carbocation, and in the fast second step a nucleophile attacks the planar cation. It is favoured by tertiary substrates, which give stable carbocations, by polar protic solvents that stabilize the ion pair, and by weak nucleophiles. Because the cation is planar, the product is often racemic and rearrangements may occur.
Going deeper: SN1 Reaction
Key ideas: Unimolecular, two-step: the leaving group departs to form a planar carbocation (slow), then the nucleophile attacks from either face, giving racemisation. Rate equals k times alkyl halide concentration. Favoured by tertiary or benzylic substrates, polar protic solvents (water, alcohols), weak nucleophiles and good leaving groups. Rearrangements are possible and E1 competes.
Common mistakes and connections: Students call tertiary halides SN2-reactive, or expect complete racemisation without noting some inversion from ion pairs. Another error is writing the rate law with the nucleophile included. Links to carbocation stability, solvolysis, stereochemistry and comparison with SN2 for choosing conditions.
Visualization of SN1 Reaction
The leaving group departs first in a slow step forming a planar carbocation; the nucleophile then attacks from either face. The interactive lesson shows this as a live animation or chart.
Worked example and use case
tert-Butyl bromide in water gives tert-butanol, (CH3)3CBr plus H2O giving (CH3)3COH.
Frequently asked questions about SN1 Reaction
What is SN1 Reaction?
A two-step unimolecular nucleophilic substitution through a carbocation, favoring tertiary substrates.
Is SN1 Reaction a beginner, intermediate or advanced topic?
SN1 Reaction 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 SN1 Reaction?
Study these earlier topics in Organic Chemistry first: Friedel-Crafts Reactions, Directing Effects, Haloalkanes.
What comes after SN1 Reaction?
The next topics in Organic Chemistry are SN2 Reaction and E1 Elimination.
Can I practise SN1 Reaction with quizzes?
Yes. The interactive lesson includes a self-check question on SN1 Reaction, and the Organic Chemistry quiz draws on every topic in this area.
Where SN1 Reaction fits in Organic Chemistry
SN1 Reaction is topic 59 of 148 in Organic Chemistry.