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 chlorideQ) Pent-2-ene R) 3-methyl pent-2-eneS) 2,3-dimethyl but-2-ene

Alkenes undergo electrophilic addition with many reagents like HX, H_2

1.	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 chlorideQ) Pent-2-ene R) 3-methyl pent-2-eneS) 2,3-dimethyl but-2-ene
Answer» `P gt Q gt R gt S ` `S gt Q gt R gt P` `S gt R gt Q gt P` `R gt S gt Q gt P` Solution :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.