Which of the following statements is / are true :

Engineering

Chemistry

Inductive Effect

Nucleophilic Substitution

Basic Concepts of GOC

Question

Which of the following statements is / are true :

Major part of energy needed for the heterolysis of C–X bond in S_N1 reaction mechanism is obtained by the solvation of X– by the polar protic solvent.

Allyl & benzyl halides undergo S_N2 reactions as they are primary halides which do not give S_N1 reaction.

Increase in the no. of phenyl ring at C of C–X causes a shift in mechanism from S_N2 to S_N1.

Greater solvation of attacking nucleophile & poor solvation of transition state promotes the reaction by S_N2 mechanism.

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Let's evaluate each statement:

Statement 1: True. The heterolysis of the C–X bond is highly endothermic. The energy required is largely provided by the solvation energy released when the polar protic solvent stabilizes the X⁻ ion.

Statement 2: False. Allyl and benzyl halides are primary but undergo S_N1 reactions readily due to resonance stabilization of the carbocation intermediate.

Statement 3: True. Adding phenyl groups increases steric hindrance and stabilizes the carbocation via resonance, favoring S_N1 over S_N2.

Statement 4: False. Greater solvation of the nucleophile makes it less reactive. Poor solvation of the transition state would destabilize it, hindering the S_N2 reaction, not promoting it.

Final Answer: Statements 1 and 3 are true.