This document provides information on SN1 and SN2 reactions, including definitions, mechanisms, kinetics, stereochemistry, reactivity, and comparisons. SN2 reactions are bimolecular, follow second-order kinetics, and result in complete stereochemical inversion. SN1 reactions are unimolecular, follow first-order kinetics, and result in racemization plus inversion through a carbocation intermediate. Key differences between the two include their order of kinetics, effects on stereochemistry, and choice of nucleophile.

2. Contents
•SN2 & SN1 Reactions.
Definition
Mechanism
Kinetics
Stereochemistry
Reactivity
• Comparison head.
• References.

3. Definition
SN2
• It is a bimolecular nucleophilic substitution
reaction between alkyl halide and strong
nucleophile wherein nucleophile displaces
halide group and forms the product.

4. Mechanism and Kinetics
The reaction between methyl bromide and
hydroxide ion to yield methanol follows second
order kinetics ;that is,the rate depends upon the
conentration of both reactants.

5. Stereochemistry
A reaction that yields a product whose
configuration is opposite to that of the reactant is
said to proceed with inversion of configuration and
is known as Walden inversion.An SN
2 reaction
proceeds with complete stereochemical inversion.

6. Reactivity
Steric hindrance
Differences in rate between two SN2
reactions are due chiefly to steric factors
and not to polar factors.

7. Definition
SN1
• It is a unimolecular nucleophilic
substitution reaction between alkyl
halide and Weak nucleophile wherein
nucleophile displaces halide group and
forms the product.

8. Mechanism and Kinetics
The reaction between tert-butyl bromide and
hydroxide ion to yield t-butyl alcohol follows
first order kinetics; that is,the rate depends upon
the concentration of only one reactant, t-butyl
bromide.

9. A single step whose rate determines the
overall rate of stepwise reaction is called
a rate determining step.

10. Stereochemistry
The SN1 reaction :
racemization plus inversion.
The nucleophilic reagent
attacks both (a) the back
side and (b)front side of the
carbocation. Back side attack
predominates.An SN1reaction
proceeds with racemization.

11. Reactivity
Ease of formation of carbocation
The more stable the carbocation the faster it
is form.

12. Comparison Head
COMPARISON
HEAD
SN2 SN1
DEFINITION Bimolecular reaction. Unimolecular reaction
MECHANISM Conc.of both
reactants.
Conc.of only one
reactants.
KINETICS Second order kinetics First order kinetics
STEREOCHEMISTRY Complete
stereochemical
inversion.
Racemization plus
inversion.
REACTIVITY CH3>1O>2O>3O 3O>2O>1O>CH3
REARRANGEMENT No rearrangement. Rearrangement occur.
CHOICE OF
NUCLEOPHILE
Strong Weak

13. References
• Morrison and Boyd,Textbook of organic
chemistry,Sixth edition, Pearson
education 2004.
• Master Organic Chemistry Llc, 1831 12th
Avenue South, #171, Nashville Tn, USA
37203.