Question

An alkyl halide by formation of Grignard's reagent
followed by hydrolysis yield butane. What is the
original alkyl halide?
(1) Ethyl halide (2) Propyl halide
(3) Butyl halide (4) Methyl halide​

Answer 1

The original alkyl hallide is (3) Butyl halide.

●On reaction with alkyl halide with magnesium metal we get magnesium alkyl halide that is gignard reagent.

●On hydrolysis this gignard reagent gives alkane.

●We get butane as final product so alkyl halide should be butyl halide.

●Butyl halide with magnesium gives Mgbutylhalide that is MgRX which is gignard reagent ,this on hydrolysis gives butane and Mg(OH)X.

●Reactions are as follow---

RX+Mg--->RMgX(gignard reagent)

CH3CH2CH2CH2Cl+Mg----->CH3CH2CH2CH2MgCl(Gignard)

RMgX+H2O-------.>RH(Mg(OH)Cl

CH3CH2CH2CH2MgCl+H2O------>Ch3CH2CH2CH3+Mg(OH)Cl

So alkyl halide is butyl halide