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Q.
There is a large difference in the boiling points of butanal and butan-$1$-ol due to
Aldehydes Ketones and Carboxylic Acids
Solution:
Butan-1-ol has intermolecular hydrogen binding while Butanal no such advantage so there is a large difference in boiling point.
Butan-1-ol has one hydrogen attached to oxygen so it can form hydrogen bond while Butanal cann't.