SN2 Nucleophilic Attack in Substitution

Steps:

• Identify reaction type: Aqueous NaOH with primary alkyl halide (1-bromopropane) undergoes SN2 mechanism.
• Recall SN2 first step: Nucleophile (OH⁻) attacks carbon from lone pair, forming partial bond.
• Match to diagram: Curly arrow shows electron movement from OH⁻ lone pair to C atom.
• Eliminate mismatches: Other options depict incorrect electron flow or bond breaking.

Why A is correct:

• In SN2, the nucleophile's lone pair donates electrons to the electrophilic carbon, per the definition of nucleophilic substitution.

Why the others are wrong:

• B: Describes C-Br bond polarization but not the initial nucleophilic attack.
• C: Reverses electron flow; Br⁻ is leaving group, not donor.
• D: Indicates radical mechanism via equal electron split, irrelevant to ionic SN2.

Final answer: A