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 =k [base][R-X]
Rate =k [base][R-X]
7.
Stereochemistry
Inversion
Stereospecific anti elimination
Comparison of SN1 and E1
SN1
E1
1.
Steps
one
one
2.
Reagent
Weakly basic
Weak base
3.
Solvent
Polar protic
Polar protic
4.
Structure
3° > 2° > 1°
3° > 2° > 1°
5.
kinetics
rate = k[R-X]
rate = k[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
rate↑
rate↑
rate↑
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