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Elimination Vs Substitution

Comparison of E2 and SN2:

 

 

SN2

E2

1

Steps

One

One

2

Reagent

Strong nucleophile

Strong bulky Bronsted base

3

Solvent

Aprotic

aprotic polar solvents

4

Phase transfer catalyst

Favours

Strongly favours

5

Influence of Structure

1° > 2° > 3°

3° > 2° > 1°

6

Kinetics

Rate is
[base][R-X]

Rate is [base][R-X]

7

Stereochemistry

Inversion

Stereospecific anti elimination

Comparison of E1 and SN1:

 

 

SN1

E1

1

Steps

Two

Two

2

Reagent

Weakly basic

 Weak base

3

Solvent

Polar protic

Polar protic

4

Structure

3° > 2° > 1°

3° > 2° > 1°

5

kinetics

Rate is [R-X]

Rate is  [R-X]

6

Stereochemistry

Racemisation

Non stereospecific

Comparison of E1, E2 and E1cB:

 

 

E1

E2

E1cB

1

Steps

2

1

2

2

Intermediate

C+

Transition state

C-

3

Structure

3° > 2° > 1°

3° > 2° > 1°

3° > 2° > 1°

4

Rate

Polar protic

Polar rate↓

Polar aprotic ↑

5

Temperature