Question

difference b/w sn1 and sn2 reaction

Answer 1

The SN1 and SN2 are both nucleophilic substitution reactions, there are some differences: 1. For SN1 reactions, the step determining the rate is unimolecular, whereas for a SN2 reaction, it is bimolecular. ... SN1 is a two-step mechanism, whereas SN2 is only a one-step process.

Answer 2

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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