Question

Predict which of the following compounds will have a lower boiling point than 1-butanal.

• A. 1-butanol
• B. 1-butene
• C. butanoic acid
• D. 2-butanol

Answer 1

Answer: (B)

1-butene will have a lower boiling point than 1-butanal. This is because the molecular weight of 1-butene is lower than that of 1-butanal.

1-butene contains 4 C atoms (apart from H atoms) and 1-butanal contains 4 C atoms and one O atom (apart from H atoms). Lower is the molecular weight, lower will be the boiling point.

1-butanol, 2-butanol and butanoic acid can form intermolecular hydrogen bonds. Hence, they will have a higher boiling point than 1-butanal which cannot form intermolecular hydrogen bonds.

Option D is correct.