Question

If the boiling point of ethanol (molecular weight = 46) is $ \text{78}{{\,}^{\text{o}}}\text{C,} $ what is the boiling point of diethyl ether ? (molecular weight =74)

• A. $ 100{{\,}^{o}}C $
• B. $ 78{{\,}^{o}}C $
• C. $ 86{{\,}^{o}}C $
• D. $ 34{{\,}^{o}}C $

Answer 1

Answer: (D)

Molecular weight of diethyl ether is more than ethanol. Therefore, it should have higher boiling point than ethanol. But it is not so. It is due to intermolecular hydrogen bonding. Ethyl alcohol has intermolecular hydrogen bonding but diethyl ether has no hydrogen bonding. The compounds shows intermolecular hydrogen bonding has higher m. p. and b. p. than compounds having no hydrogen bonding. Therefore, the boiling point of diethyl ether will be less than ethanol $ \text{(7}{{\text{8}}^{\text{o}}}\text{)}\text{.} $