S.No

Sn1

(Uni molecular Nuclieophilic Substitution Reaction )

Sn2

(Bi molecular Nuclieophilic Substitution Reaction)

1

The rate of the reaction depends only on the concentration of the alkylhalide only

Rate α [RX].

∴ it is also called as

Nuclieophilic Substitution FIRST order Reaction

The rate of the reaction depends on both the concentration of the alkylhalide and concentration of the nuclieophile

Rate α [RX][:Z^-]

∴ it is also called as

Nuclieophilic Substitution SECOND order Reaction

2

It is done in 2 steps.

1. slow step(Rate determining Step)

2.fast step

It is done in 1 step.

1.slow step(rate determining step)

3

Order of reactivity of Alkyl halides towards Sn1

3>2>1>CH3X

Order of reactivity of Alkyl halides towards Sn2

3<2<1<CH3X

4

In this reaction racemisation takes place because nucleiophile has a chance to attack from both sides.

In this reaction complete walden inversion is possible.because here only one side attack is possible that to exactily opposite.

5

Intermediate stage is possible. Because of formation of stable carbocation

Transition state is possible, it is only imaginary one not existed one

6

Rearrangement is possible.

Rearrangement is not possible.

7

Secondary alkyl halides in the presence of polar(protic) solvents undergo Sn1 reaction

Secondary alkyl halides in the presence of non polar solvents undergo Sn2 reaction.

8

It follows 1^st order kinetics.

It follows 2^nd order kinetics.

9

Bonding is very temporary and lasts very soon

Bonding is somewhat strong both species come together for a time.

10

It involves weak nuclieophiles

It involves strong nuclieophiles