Vapor Pressure: H-bonding vs. dipole-dipole attraction
The molecular formulas for butanol and diethyl ether are the same. However, their structures are very different. Butanol molecules form hydrogen bonds, while diethyl ether molecules can only form dipole-dipole interactions. Which force is stronger?
When butanol is injected into the open end of the barometer, the butanol rises to the top and vaporizes. The mercury column is depressed to 721 millimeters. When diethyl ether is injected, the diethyl ether rises to the top and vaporizes. The mercury column is depressed to 264 millimeters.
Diethyl ether has a much higher vapor pressure than butanol. Diethyl ether has only intermolecular dipole-dipole forces, much weaker than the hydrogen-bond intermolecular forces of the butanol.
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