Alkenes undergo electrophilic addition with many reagents like HX, `H_2O`, HOCI etc. Except in the case of addition of `X_2^(-)` in other additions carbocation is formed as intermediate. The rate of such reactions depends on the stability of carbocation. Rearrangements and ring expansion are also common in such reactions.
The correct order of reactivity of the following towards electrophilic addition is
P) Vinyl chloride Q) Pent-2-ene
R) 3-methyl pent-2-ene S) 2,3-dimethyl but-2-ene

Options

A. `P gt Q gt R gt S `
B. `S gt Q gt R gt P`
C. `S gt R gt Q gt P`
D. `R gt S gt Q gt P`

Answer

C

Explanation

P with `Cl` is least reactive as it exerts -I effect and destablises the intermediate carbocations formed Among others the carbocations formed from S, R, Q are

Stability decreases a number of `alpha-H` atom decreases reactively decreases.