Predict all order of reactivity of the following compounds in dehydrohalogenation.
a,. I. `CH_(3)CH_(2)CH_(2)CH_(2)Cl`
II. `(CH_(3))_(2)CHCH_(2)Cl`
III. `(CH_(3))_(2)CH - CH_(2)Br`
IV. `CH_(3)CH(Br)CH_(2)CH_(3)`
V. `(CH_(3))_(3) C - Br`
b. I. `CH_(3)CH(Br)CH_(3)`
II. `CH_(3)CH_(2)CH_(2)Br`
III. `(CH_(3))_(2) CH - CH_(2) Br`
IV. `(CH_(3))_(3)C - CH_(2) Br`

Explanation

Ease fo dehdrohalogenation is due to the formation of carbocation and the stability of carbocation is `3^(@) gt 2^(@) gt 1^(@)`, and case of fornation of carbocation is `(R-1) gt (R-Br) gt (R-Cl)`
So the order of dehydrogenation is `(V) gt (III) gt (II) gt (IV) gt (I)`.