The variation can be established by intermolecular hydrogen bonding, where alcoholic hydrogen is bound to a strongly electronegative oxygen atom to give rise to dipole of the form, Et-Oδ- - Hδ+ which arises the boiling point.
Wheareas, C-O bonds in dimethyl ether are polar. Carbon bonded with hydrogen is moderately electronegative compared to oxygen. In the absence of intermolecular bonding, ether becomes more volatile.
