Elimination reaction mechanism-E1 and E2 mechanism and reaction.

In this blog post, you will learn about e1 and e2 reactions and e1 and e2 mechanisms as well. If you want to learn about SN1 and SN2 reaction–>sn1 and sn2 reactions

Elimination reaction-:

Elimination reaction is also known as α,β elimination reaction or dehydrohalogenation reaction.

For eg-:

CH3-CH2-CH2-Br + alc.KOH -> CH3-CH=CH2 + KBr+H2O

# satyzeff’s rule-:

Satyzeff’s rule states that ‘’ in the elimination reaction of alkyl halides, possibility of formation off more substituted alkene is high because its stability is high.

# E2 reaction mechanism-:

E2 reaction-:

E2 reaction is such a reaction which depends on the concentration of substrate as well as the concentration of base. E2 reaction is a second order reaction.

In E2 reaction;

Rate α [substrate][base]

1° alkyl halides follow E2 reaction mechanism.

In E2 reaction mechanism, base abstracts β hydrogen from substrate because β-hydrogen are more acidic.

For e.g.-:

# E1 reaction mechanism(alc.KOH dehydrohalogenation reaction)

E1 raction mechanism is such a reaction in which the rate of reaction depends on the concentration of substrate only.

Rate α [Substrate]

For eg-: 3° alkyl halides will follow E1-elimination reaction mechanism.

Mechanism-:

Step 1-: slow ionization to give carbocation

Step 2-: base absorbs β-hydrogen from carbocation

Step 1 explanation-:

3° alkyl halides undergo slow ionization to give 3° carbocation which is reactive, trigonal planar, sp² hybridized, having bond angle 120°.

Step 2 explanation-:

Base can absorb the β-hydrogen from tertiary carbocation due to having more acidic nature.

So alkene is produced.

E2 mechanismE1 mechanism
  1. E2 mechanism is a bimolecular reaction.
  2. Rate α [substrate][base]
  3. Strong base favors E2 mechanism.
  4. Non-polar solvent favors E2 mechanism.
  5. For eg-: general de-hydro halogenation of 1° alkyl halides.
  1. But E1 mechanism is unimolecular.
  2. Rate α [substrate]
  3. But weak base favors E1 mechanism.
  4. But polar solvent favors E1 mechanism.
  5. But for eg-: de-hydro halogenation of 3° alkyl halides.

Elimination reaction-:

Elimination reaction is also known as α,β elimination reaction or dehydrohalogenation reaction.

For eg-:

CH3-CH2-CH2-Br + alc.KOH -> CH3-CH=CH2 + KBr+H2O

# satyzeff’s rule-:

Satyzeff’s rule states that ‘’ in the elimination reaction of alkyl halides, possibility of formation off more substituted alkene is high because its stability is high.

# E2 reaction mechanism-:

E2 reaction-:

E2 reaction is such a reaction which depends on the concentration of substrate as well as the concentration of base. E2 reaction is a second order reaction.

In E2 reaction;

Rate α [substrate][base]

1° alkyl halides follow E2 reaction mechanism.

In E2 reaction mechanism, base abstracts β hydrogen from substrate because β-hydrogen are more acidic.

For e.g.-:

# E1 reaction mechanism(alc.KOH dehydrohalogenation reaction)

E1 raction mechanism is such a reaction in which the rate of reaction depends on the concentration of substrate only.

Rate α [Substrate]

For eg-: 3° alkyl halides will follow E1-elimination reaction mechanism.

Mechanism-:

Step 1-: slow ionization to give carbocation

Step 2-: base absorbs β-hydrogen from carbocation

Step 1 explanation-:

3° alkyl halides undergo slow ionization to give 3° carbocation which is reactive, trigonal planar, sp² hybridized, having bond angle 120°.

Step 2 explanation-:

Base can absorb the β-hydrogen from tertiary carbocation due to having more acidic nature.

So alkene is produced.

E2 mechanismE1 mechanism
  1. E2 mechanism is a bimolecular reaction.
  2. Rate α [substrate][base]
  3. Strong base favors E2 mechanism.
  4. Non-polar solvent favors E2 mechanism.
  5. For eg-: general de-hydro halogenation of 1° alkyl halides.
  1. But E1 mechanism is unimolecular.
  2. Rate α [substrate]
  3. But weak base favors E1 mechanism.
  4. But polar solvent favors E1 mechanism.
  5. But for eg-: de-hydro halogenation of 3° alkyl halides.

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