Attack of nucleophile at a saturated carbon atom bearing substituent, known as leaving group results in Substitution reaction. The group that is displaced (leaving group) carries its bonding electrons. The new bond is formed between nucleophile and the carbon using the electrons supplied by the nucleophilic agent. The compound on which substitution takes place is called “substrate.” The substrate consists of two parts, alkyl group and leaving group.

1. Seminar presented on,
“Nucleophilic Substitution reaction (SN1 reaction)”
Presented by
Shashikumar S
Register No: P11AZ22S104036
I M.Sc., I Semester.

2. CONTENTS
 INTRODUCTION
 SN1 REACTION
 CONCLUSION
 REFERENCE
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3. INTRODUCTION
• Attack of nucleophile at a saturated carbon atom bearing substituent, known as
leaving group results in Substitution reaction.
• The group that is displaced (leaving group) carries its bonding electrons.
• The new bond is formed between nucleophile and the carbon using the electrons
supplied by the nucleophilic agent.
• The compound on which substitution takes place is called “substrate.”
• The substrate consists of two parts, alkyl group and leaving group.
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4. SN1 REACTION
• Unimolecular Nucleophilic Substitution reaction
• An SN1 reaction proceeds in two steps.
• The first step(slow step) is the rate determining step and involves
the ionisation of reactant to form a carbocation intermediate.
• The breaking of C-X bond in RX takes place in a heterolytic fission,
in which both the bonding electrons go to the leaving group.
• The second step (fast step),the intermediate carbocation is attacked
by the nucleophile to give the final product.
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5. SN1 Reaction occurs in two steps.
Step I : In first step, the carbon-halogen bond of tertiary butyl bromide
slowly breaks heterolytically to form an intermediate carbocation i.e.
Tert-butyl carbocation.
Step II : The carbocation formed combines rapidly with nucleophile i.e.
OH– to give tertiary butyl alcohol.
Mechanism : SN1 Reaction
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6. Factors Affecting SN1 Reaction
• Effect of solvent :The solvent plays an important role in SN1
reactions as the energy required to effect the initial ionization is
largely recovered from the energy evolved through solvation of
the resulting ion pair.
• Effect of leaving group on rate:
The rate of SN1 reaction is largely influenced by the nature of the
leaving group. The rate of ionization is affected by the stability of
the leaving group,X.
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7. Energy profile diagram of SN1 reaction:
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8. Conclusion
The rate of an SN1 reaction is only dependent on the concentration
of the alkyl halide. The higher the concentration, the faster the
rate of reaction. The nature of the alkyl halide also affects the rate
of reaction. Tertiary alkyl halides react faster than secondary and
primary alkyl halides.
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9. Reference
• Reactions and Reagents by Dr. O P Agarwal.
• Organic Chemistry by Jonathan Clayden,Nick Greeves and
Stuart Warren. (2nd Edition)
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10. Thank you
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