What is the IUPAC name of the major product formed when crotonaldehyde (but-2-enal) is treated with sodium borohydride ( NaBH ₄ )?

Step-by-step solution

Crotonaldehyde (but-2-enal) contains two reducible functional groups: an aldehyde and a carbon-carbon double bond. Sodium borohydride ( NaBH ₄ ) is a mild reducing agent that selectively reduces the aldehyde group to a primary alcohol. It generally does not reduce isolated or conjugated carbon-carbon double bonds under standard conditions. Therefore, the reduction of but-2-enal yields but-2-en-1-ol. Reduction of both groups to yield butan-1-ol would require catalytic hydrogenation (e.g., H ₂/ Ni ). Answer: But-2-en