SN2 mechanism for primary haloalkane hydrolysis

Steps:

• Hydrolysis of haloalkanes with aqueous NaOH is nucleophilic substitution.
• Primary haloalkanes follow SN2 mechanism, bimolecular in the rate-determining step.
• First step of SN2: OH⁻ nucleophile attacks the electrophilic carbon of the haloalkane.
• Two species react together: the primary haloalkane and the nucleophile OH⁻.
• Tertiary haloalkanes follow SN1, with unimolecular first step (C–X bond breaks alone).

Why B is correct:

• B specifies primary haloalkane, where the first step involves reaction with a nucleophile (OH⁻), as defined in the SN2 mechanism.

Why the others are wrong:

• A: For primary, the other reacting species is nucleophile OH⁻, not electrophile.
• C: Tertiary haloalkane uses SN1; first step is unimolecular, no second species reacts.
• D: Tertiary haloalkane's SN1 first step involves only one species, not two reacting together.

Final answer: B