Statement-I : The conversion proceeds well in the less polar medium.
CH2−OH+Cl−
Statement-II : The conversion proceeds well in the more polar medium.
In the light of the above statements, choose the correct answer from the options given below.
(A)Both statement I and statement II are true✓ Correct
(B)Both statement I and statement II are false
(C)Statement I is false but statement II is true
(D)Statement I is true but statement II is false
Answer: (A)
Solution
Consider the two SN2 substitutions.
In the first, a neutral alkyl chloride is attacked by the charged nucleophile OH−: the reactant side carries concentrated negative charge on the incoming OH−, while in the pentacoordinate transition state that charge is spread over the incipient C⋯OH and C⋯Cl partial bonds, so the transition state has lower charge density than the reactants. A less polar medium does not selectively stabilise the more charge-concentrated reactant relative to this diffuse transition state, so the activation energy stays low and the substitution proceeds well in a less polar medium — Statement I is true.
In the second, a neutral amine R3N attacks the neutral alkyl chloride: charge develops only in the transition state, as the incipient C−Cl bond breaks and nitrogen becomes positively charged. A more polar medium stabilises this now more charge-separated transition state relative to the neutral reactants, lowering the activation energy, so this substitution is favoured by a more polar medium — Statement II is true.
Both statements are true.
JEE Main · 2025 · 24 Jan 2025 · Shift 1 · Single correct option
