difference b/w sn1 and sn2 reaction
Answers
Hey !!
Sn1 Reaction
First order kinetics.
Two-step reaction
Carbocations are intermediates
Both backside and front side attack of the nucleophile occurs through the backside attack predominates.
Generally racemization with some inversion, partial racemization is observed.
Rearrangement are generally observed.
Elimination is an important side reaction.
Electronic factors affect the reaction rates generally.
The order of reactivity follows the sequence : ( 3° > 2° > 1° methyl halides )
Weak nucleophiles such as water, alcohols, etc favour these reactions.
Low concentration of the nucleophiles generally favour them.
Polar protic solvents ( water , alcohols , acids ) of high dielectric constants favour Sn1 reaction.
Sn2 reaction
Second order kinetics.
One-step reaction.
Carbocations are not intermediates. The reaction occurs through a transition state.
Exclusive backside attack of the nuclephile takes place.
Complete inversion of configuration occurs.
Rearrangements are not observed.
Elimination is not an important side reaction.
Steric , and not electronic factors, affect the rates of the reactions.
The order of reactivity follows the sequence : Methyl > 1° > 2° > 3° alkyl halides.
Strong nucleophiles such as alkoxide ions favour these reactions.
High concentration of the nucleophiles favour them.
Polar aprotic solvents ( acetone , acetonitrile , dimethyl formamide , dimethyl sulphoxide etc. ) of high dielectric constants favour Sn2 reactions. However, methanol and ethanol are usually used since they are inexpensive and can be easily removed after the reaction.
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