Which of the following alkyl halide is most reactive towards substitution by S_NI mechanism?

CONCEPT:

SNI Mechanism

• SNI (Substitution Nucleophilic Internal) mechanism is a type of nucleophilic substitution reaction where the nucleophile is introduced internally in the molecule.
• The reactivity of alkyl halides towards SNI mechanism depends on the leaving group ability, where a better leaving group increases the reactivity.
• In SNI mechanism, the leaving group should be able to stabilize the negative charge that develops during the transition state.

EXPLANATION:​

• The leaving group ability of halogens decreases in the order: I > Br > Cl > F.
• Iodine (I) is the best leaving group among the halides mentioned because it is larger and can stabilize the negative charge more effectively.
• Therefore, (CH₃)₃C-I will be the most reactive towards substitution by the SNI mechanism.

Therefore, the correct answer is (CH₃)₃C-I.