Sn1 and sn2 reaction

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1. THE H.N.S.B LTD. SCIENCE COLLEGE, HIMATNAGAR
CLASS SEMINAR
M.ScSEM-I
Subject :-INORGANIC CHEMISTRY
Paper :-CHN-401
Topic :-Nucleophilic displacement reaction
Presented By Guided By
KajalPatel Dr. N. I. Patel sir

2. Content……
-SN1 Reaction
-SN2 Reaction

3. The S
N1Reaction
Substitution
Nucleophilic
Unimolecular

4. The S
N1Reaction
SN1 reactions are nucleophilic substitutions, involvinga
nucleophile replacing a leaving group (just likeSN2).
However:SN1reactionsareunimolecular:therate
ofthisreactiondependsonlyontheconcentration
ofonereactant.
●SN1 reactions happen in twosteps:
1.The leaving group leaves, and the substrate formsa
carbocationintermediate.
2.The nucleophile attacks the carbocation, formingthe
product.

5. The S
N1Reaction
Carbocation
Intermediate
Substrate
Products

6. The S
N1Reaction
1. The SlowStep:
First step of the SN1reaction:
The leaving group leaves, and the substrate carbon now only hasthre
●Carbocations are most stable when there are more atoms todistribute
●Carbocationstability:
3º > 2º >>1º
●Tip: study the difference between reaction intermediates and transitionstate

7. The S
N1Reaction
2. The FastStep:
Second step of the SN1reaction:
The nucleophile attacks the carbocation intermediate, bringing itsele
●The substrate loses any stereospecificity during the carbocationinter

8. The S
N2Reaction
Substitution
Nucleophilic
Bimolecular

9. The S
N2Reaction
Substitution: this reaction involves a
substitution of players –two reactants produce
two products, in which some things have been
switchedaround:
AB + C AC +B
●Tip: think of this if you get elimination (E1 and E2)
reactions mixed up with substitution (SN1 andSN2)
reactions.

10. The S
N2Reaction
TransitionState
SN2summary:
(1)Nucleophile back-side attacks the δ+ carboncenter.
(2)Transition state forms in which nucleophile is formingbo
(3)The leaving group leaves, forming the finalproduct.
(2)
(1)
(3)

11. The S
N2Reaction
Nucleophilic: these reactions involve a
nucleophile (Nuc:
-
) replacing a leavinggroup.
●Nucleophiles attack the substrate, donatingan
electron pair to the new bond, and replacing
the leaving group (asubstitution).
●Tip: Remember the role of a nucleophile by its Greek
roots: Nucleo-(nucleus)-phile-(lover) –it is attracted to
the nucleus, which is positively charged! Nucleophilesare
therefore negatively charged or stronglyδ-.

12. The S
N2Reaction
Substrate
Nucleophile
LeavingGroup
Product

13. The S
N2Reaction
Bimolecular: A bimolecular reaction is one
whose rate depends on the concentrationsof
two of itsreactants.
●SN2reactionshappeninonestep–the
nucleophileattacksthesubstrateasthe
leavinggroupleavesthesubstrate.
●Tip: Recall that the rate of a reaction depends on the
slowest step. In bimolecular reactions, therefore, theslow
step involves two reactants. For SN2 reactions, there are
only two reactants; this means that the slow step is the
onlystep.

14. The S
N2Reaction
Notes:
●In the SN2 reaction, the nucleophile attacks from the
most δ+region
●This back-side attack causes an inversion (study the previousslide)
●The nucleophile must be able to reach the δ+ carbon center that itis
●Tip: see chapter 6 of your textbook to learn what makes a good nucleophileo