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please explain sn1 and sn2

please explain sn1 and sn2

Grade:12th pass

2 Answers

Aarti Gupta
askIITians Faculty 300 Points
7 years ago
Nucleophilic substitution reactions are of two types according to the mechanisms they follow--
SN1 reaction – SN1 reaction is reffered to as substitution nucleophilic unimolecular reaction.In such reaction only one molecule is involved in rate determinig step and it is written as SN1.It is found that such type of reactions are generally carried out in polar protic solvents like H2O,alcohol,acetic acid etc.
For ex- reaction between ter-butyl bromide and OH- to form tert-butyl alcohol follows such type of reaction.
(CH3)3C--Br + OH-- ---------->. (CH3)3C--OH + Br--
The rate of above reaction can be expressed as--
Rate = k[(CH3)3C-Br]
Since concentration of only one of the reactant involves in rate determination i.e one molecule is involved in determining the rate of raection,so it is SN1 reaction.
SN2 reaction– This is reffered to as substitution nucleophilic bimolecular because two molecules participate in determining the rate of the reaction.
For ex- reaction between methyl bromide and OH- to form methanol.
CH3Br + OH- ------------> CH2OH + Br--
Rate of the reaction is expressed as--
Rate = k[CH3Br][OH-]
Since rate depends on the concentrations of both the reactants i.e two molecules are involved so it follows second order kinetics.
Adarsh
733 Points
7 years ago
please check this comparison

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