Class 12 Chemistry Haloalkanes and Haloarenes Conditions of E2 reaction

Conditions of E2 reaction:

The conditions favoring SN2 reaction favors E2 reactions which are as follows:

Alkyl halide: SN2 reaction will be slowed down if there exists steric congestion around the carbon atom undergoing the inversion process.

i.e. we conclude that if there is less congestion then the reaction will be faster.

CH3X > RCH2X  >> R2CHX >>> R3CX

Leaving group: the leaving group with a full negative charge is always expelled out. As a result the best leaving groups are those that can best stabilize an anion.

Solvent: Surroundings which the solvent surrounds can cause a reaction to go faster or slower. Solvent are of two types:

  1. Protic solvent: Nucleophile suffers salvation in which protic solvent hydrogen bonds with anion that tries to attack the alkyl halide thus creating a shield around the nucleophiles. As a result reaction is slowed down. E.g. Alcohol, water
  2. Aprotic (polar) solvent: Aprotic solvents are those not capable of donating H's. Due to which it's favorable in SN2 reaction because it's a 1step reaction and it doesn't require forming or having H's to stabilize the Carbocation step. E.g. Acetone, DMSO.

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