1. The document summarizes nucleophilic substitution reactions (SN1 and SN2). It defines nucleophiles as negatively charged or neutral species with a lone pair of electrons. 2. It describes the mechanism of the SN1 reaction, which is unimolecular and involves the rate being dependent only on the concentration of the substrate. It forms a carbocation intermediate. 3. It also describes the concerted bimolecular SN2 reaction mechanism where the nucleophile attacks the substrate from the backside in a single transition state, causing inversion of configuration. Factors favoring each reaction type are also discussed.

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S.T FRANCIS DE SALES COLLEGE,
SEMINARY HILLS,NAGPUR
DEPARTMENT OF CHEMISTRY
SEMINAR BY:
Mr. PRATIK DEVRAO MIRCHE
(M.sc:- 1st SEMESTER)
GUIDED BY:- SNEHA JHADAO MAM
TOPIC NAME:-

2. NUCLEOPHILIC SUBSTITUTION REACTIONS
NUCLEOPHILES
⚫The word nucleophile comes from nucleus, the
positivepartof an atom, plus -phile from Greek word
philos meaning to love.
⚫A nucleophile is any negative ion orany neutral
molecule that hasat least one unshared electron
pair. Eg:
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4. MECHANISM OF SN1 REACTION
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⚫The SN1 reaction is a Substitution, Nucleophilic and
Unimolecular. The reaction of tert-butyl chloride with
sodium hydroxide in a mixture of water and acetone to
form tert-butyl alcohol is a good example for SN1
reaction.
⚫The rate of formation of tert-butyl alcohol is dependent
only on the concentration of tert-butyl chloride and
independent of the concentration of hydroxide ion.
The rate equation for this substitution reaction is first
orderwith respectto tert-butyl chloride.

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6. A free-energy diagram for the SN1 reaction of tert-
butyl chloride with water
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7. STEREOCHEMISTRY OF SN1 REACTIONS
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8. MECHANISM OF SN2 REACTION
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9. ⚫The SN2 reaction
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is a Substitution,
Nucleophilic, bimolecular reaction. The
transition state involves both the nucleophile and
the substrate, it accounts for the observed second-
orderreaction rate.
⚫The mechanism for SN2 reaction was proposed
by Edward D. Hughes and Sir Christopher Ingold
(the University College, London) in 1937.

10. ⚫ The nucleophile attacks the carbon bearing the leaving group from the back
side.
⚫ The orbital that contains the electron pair of the nucleophile begins to overlap
withanempty(antibonding)orbitalofthecarbonbearingtheleavinggroup.
⚫ The bond between the nucleophile and the carbon atom is forming, and the
bond between the carbon atom and the leaving group is breaking at the same
time.
⚫ Because bond formation and bond breaking occur simultaneously in a single
transitionstate,theSN2reactionisaconcertedreaction.
⚫ TheconfigurationofthecarbonatombecomesinvertedduringSN2reaction.
⚫ ThereactionisaexothermicreactionwherethefreeenergyvalueGisnegative.
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12. A free-energy diagram for a hypothetical SN2 reaction that
takes place with a negative value of G°
1. Most of the SN2 chemical reactions occur much more rapidly at higher
temperatures.
2. A reaction with a lower free energy of activation will occur very much
faster than a reaction with a higher one.
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13. THE STEREOCHEMISTRY OF SN2 REACTIONS
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14. FACTORS FAVOURING SN1 &SN2
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REFERENCES

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ACKNOWLEDGEMENT
ST FRANCIS DE SALES COLLEGE,NAGPUR
• Dr .K .T Thomas Sir (Principal)
• Prof.M.karmarkar Sir(HOD of chemistry Department )
• Ms .Nikita Gupta Mam
• Ms .Rasmi Tiwari Mam
• Dr.Sneha Jhadao Mam
• Ms.Sheetal Pal Mam

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