Nucleophilic addition targets electrophilic sites like carbonyl carbons

Steps:

• Define nucleophilic addition as a reaction where a nucleophile attacks an electron-deficient center, common in unsaturated or polar bonds.
• Identify functional groups: carbonyl (C=O) in aldehydes enables this due to partial positive charge on carbon.
• Evaluate options: scan for C=O presence and rule out saturated or substitution-prone structures.
• Select the compound with aldehyde functionality for nucleophilic addition.

Why B is correct:

• Ethanal (CH3CHO) contains a carbonyl group where the carbon is electrophilic, allowing nucleophiles to add per the mechanism of carbonyl addition reactions.

Why the others are wrong:

• A: Bromoethane (CH3CH2Br) undergoes nucleophilic substitution at the carbon-halogen bond, not addition.
• C: Ethane (C2H6) is a nonpolar alkane with no electrophilic site for addition.
• D: Ethene (C2H4) features a C=C bond that attracts electrophilic addition, not nucleophilic.

Final answer: B