Class 12 Chemistry Haloalkanes and Haloarenes SN2 mechanism

SN2 mechanism

In case of SN2 reactions the halide ion leaves from the front side whereas the nucleophiles attacks from the back side; due to this reason SN2 reactions are always accompanied by the inversion of configuration. Thus formation of another enantiomer is lead by SN2 reaction of an optically active halide i.e. optical activity is retained but with opposite configuration.

Stereochemistry of SN2:   

 

 

Key features:

In SN2 reaction the stereochemistry around carbon atom of the substrate undergoes inversion and is known as walden inversion.

The rate of reaction depends on the steric bulk of the alkyl group.

Increase in the length of alkyl group decreases the rate of reaction. Alkyl branching next to the leaving group decreases the rate drastically.

Under the following conditions SN1 and SN2 reactions take place:

  • The alkyl is secondary and tertiary.
  • The solvent is Protic or Aprotic.
  • To stabilize the intermediate stage.

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