Alcoholic KCN enables SN2 formation of nitriles from primary alkyl halides

Steps:

• Identify pentanenitrile (CH3(CH2)3CN) forms via SN2 reaction of 1-bromobutane (CH3(CH2)3Br) with CN-.
• Recognize KCN provides CN- nucleophile for substitution.
• Note standard condition requires ethanol solvent to dissolve KCN and favor SN2 over elimination or side reactions.
• Match options: only B specifies ethanol solvent with heat and KCN.

Why B is correct:

• Ethanol as solvent dissolves KCN fully, promoting clean SN2 displacement to yield the nitrile without hydrolysis.

Why the others are wrong:

• A: Lacks solvent specification; aqueous conditions lead to KCN hydrolysis, reducing CN- availability.
• C: Identical to A; no ethanol means incomplete reaction or side products like alcohols.
• D: Ethanol alone provides no CN- source, so no substitution occurs.

Final answer: B