Physical Properties

The C–O bonds on either side of the ether oxygen are individually polar, so an ether molecule as a whole carries a net dipole moment. Even so, this polarity is too weak to have much effect on boiling point — an ether's boiling point tracks that of an alkane of comparable molar mass far more closely than it tracks that of an alcohol of the same molar mass. The comparison is stark when the three are placed side by side:

Pentane and ethoxyethane, though structurally very different, boil almost identically — while butan-1-ol, built from the same number of heavy atoms, boils roughly 80 K higher.

That gap between the alcohol and the ether comes down to hydrogen bonding: an alcohol's O–H can hydrogen-bond to another alcohol molecule, but an ether has no O–H of its own to offer, so ether molecules cannot hydrogen-bond to each other. Without that extra intermolecular attraction, far less energy is needed to separate ether molecules into the vapour phase. …