The correct order of reactivity in S_(N)1 reaction for the following compounds is- underset((I))underset(Cl)underset(|)(CH_(3)-CH-CH_(2)-CH_(3)), underset((II))(Ph-underset(Cl)underset(|)(C)H-CH_(2)-CH_(3)) underset((III))(CH_(3)-underset(OCH_3)underset(|)overset(Cl)overset(|)(C)-CH_(3)) , CH_(3)-CH_(2)-CH_(2)-Cl

The correct order of reactivity in S_(N)1 reaction for the following c

1.	The correct order of reactivity in S_(N)1 reaction for the following compounds is- underset((I))underset(Cl)underset(\|)(CH_(3)-CH-CH_(2)-CH_(3)), underset((II))(Ph-underset(Cl)underset(\|)(C)H-CH_(2)-CH_(3)) underset((III))(CH_(3)-underset(OCH_3)underset(\|)overset(Cl)overset(\|)(C)-CH_(3)) , CH_(3)-CH_(2)-CH_(2)-Cl
Answer» I GT II gt III gtIV II gt I gt III gt IV III gt II gt I gt IV IV gt III gt II gt I Solution :`S_(N)1` reaction proceeds via formation of carbocation INTERMEDIATE. Thus more stable the carbocation, more reactive is the parent alkyl HALIDE towards `S_(N)1` reaction. Compound (III) gives `2^(@)` carbocation which is stabilised by +M effect of -OME group. Thus it is the most stable carbocation. Compound (II) gives benzylic carbocation which is resonance stabilised. We know `2^(@)` carbocation is more stable than `1^(@)` carbocation. Therefore, the correct order of recactivity of `S_(N)1` reaction is III > II > I > IV.