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explain in detail about SN1 and SN2 reactions
SN1 ) this reaction proceeds according to these steps 1) hetrolatically cleavage of carbon halogen bond 2)formation of carbocation(rearrangment) 3)formation of new bond eg) CH3CH2CH2Cl + KOH (aq) = CH3CH(OH)CH3 mechanism CH3CH2CH2Cl = CH3CH2CH2+ ( 1O CARBOCATION) 1o carbocation rearranges to 2o by hydride shift , to gain stablity ... CH3CH+CH3 + OH- (neucleophile) = CH3CH(OH)CH3 order of reactivity = benzyl>allyle>3o >2o>1o (on the basis of carbocation stablity)) SN2) in this reaction breaking of bonds & formation of new bonds take place samultaneously during a transition state... in this state neuclephile(OH-) attacks from back side and at the same time carbon halogen bond breaks and product is formed... this transition state is pentavalent & attaking neuclophile ,halogen are along axial bond ......no rearrangment occures... eg) CH3CH2CH2Cl + OH- => CH3CH2CH2OH this reaction favoures aprotic solvents & strong base ...... order of reactivity = 10>2o>30 (less staric hindered alkyle halide will react fast )
SN1 ) this reaction proceeds according to these steps
1) hetrolatically cleavage of carbon halogen bond
2)formation of carbocation(rearrangment)
3)formation of new bond
eg) CH3CH2CH2Cl + KOH (aq) = CH3CH(OH)CH3
mechanism
CH3CH2CH2Cl = CH3CH2CH2+ ( 1O CARBOCATION)
1o carbocation rearranges to 2o by hydride shift , to gain stablity ...
CH3CH+CH3 + OH- (neucleophile) = CH3CH(OH)CH3
order of reactivity = benzyl>allyle>3o >2o>1o (on the basis of carbocation stablity))
SN2)
in this reaction breaking of bonds & formation of new bonds take place samultaneously during a transition state...
in this state neuclephile(OH-) attacks from back side and at the same time carbon halogen bond breaks and product is formed...
this transition state is pentavalent & attaking neuclophile ,halogen are along axial bond ......no rearrangment occures...
eg)
CH3CH2CH2Cl + OH- => CH3CH2CH2OH
this reaction favoures aprotic solvents & strong base ......
order of reactivity = 10>2o>30 (less staric hindered alkyle halide will react fast )
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