Alcohols, Phenols and Ethers Part 1

An ether and an alcohol having the same molecular formula are functional isomers of each other. For example, for the molecular formula $\mathrm{C_2H_6O}$ : alcohol is $\mathrm{CH_3CH_2OH}$ (ethanol) ether is $\mathrm{CH_3-O-CH_3}$ (dimethyl ether) The alcohol molecule contains an $\mathrm{-OH}$ group, so its molecules are held together by strong intermolecular hydrogen bonding. The ether molecule has no $\mathrm{-OH}$ group, so its molecules are held together only by weak van der Waals forces (dipole–dipole interactions). Because of this strong intermolecular hydrogen bonding, the molecules of the alcohol remain strongly associated and a much larger amount of energy is needed to separate them. Therefore the alcohol has a higher boiling point and a lower vapour pressure, i.e. it is less volatile. Hence an ether is more volatile than an alcohol having the same molecular formula, and the correct option is: intermolecular hydrogen bonding in alcohols. In alcohol inter-molecular hydrogen bonding look like this -