»»
Sn1 reactions is based on stability of carbocation as
order of stability of carbocation is 3>2>1degree.
Hence, order of stability of haloalkanes is 3>2>1 degree haloalkanes.
»greater the stability of carbocation
greater the reactivity of corresponding haloalkane towards Sn1reactions
»therefore sn1 reactions directly proportional to stability of carbocation .


»»Sn2 reactions are based on stearic hindrance which changes the product formed from dextrorotatory to laevorotatory or vice versa.
»Here order of stability of halo alkanes is 1>2>3 degree haloalkanes.
» greater the stearic hindrance
lesser the speed of sn2 reactions.
»therefore
sn2 reactions are inversely proportional to stearic hindrance.