The order of reactivity of the following alcohols

`underset(III)(CH_(3)-CH_(2)-overset(CH_(3))overset(|)(CH)-OH)` , `underset(IV)(OH-CH_(2)-overset(CH_(3))overset(|)(CH)-CH_(3))`
towards hydrogen halide is

Options

A. `I gt II gt III gt IV`
B. `I lt II lt III lt IV`
C. `II gt III gt IV gt I`
D. `II gt III gt I gt IV`

Answer

A

Explanation

For a given HX, the reactivity of alcohol depends on the stability of carbocation formed. The order of stability of carbocation is Benzyl `gt 3^(@) gt 2^(@) gt 1^(@)`.
The order of reactivity of alcohols is therefore
`{:(I,gt,II ,gt,III ,gt,IV),(("Benzyl"),,(3^(@)),,(2^(@)),,(1^(@))):}`