Consider the following statements about the physical properties of ethers.
(A) The C–O bonds in ethers are polar, and thus ethers have a net dipole moment.
(B) The boiling points of ethers are comparable to those of the alcohols of comparable molecular masses.
(C) Ethoxyethane and butan-1-ol are miscible with water to almost the same extent.
(D) The large difference in the boiling points of alcohols and ethers is due to the presence of hydrogen bonding in alcohols.
Which of the statements given above are correct? Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (C) and (D) only
Ether molecules have no O–H group, so they cannot form hydrogen bonds with one another. Their oxygen atom can still form hydrogen bonds with water. This decides both their boiling points and their miscibility with water.
(A) The C–O bonds in ethers are polar, and thus ethers have a net dipole moment. — True. Oxygen is more electronegative than carbon, so each C–O bond is polar and the ether molecule has a net dipole moment. This polarity is weak.
(B) The boiling points of ethers are comparable to those of the alcohols of comparable molecular masses. — False. The weak polarity of ethers hardly affects their boiling points, which are comparable to those of the alkanes of comparable molecular masses: ethoxyethane boils at 307.6 K and n-pentane at 309.1 K. Butan-1-ol boils much higher, at 390 K.
(C) Ethoxyethane and butan-1-ol are miscible with water to almost the same extent. — True. About 7.5 g of ethoxyethane and 9 g of butan-1-ol mix with 100 mL of water, because the oxygen of the ether, like that of the alcohol, forms hydrogen bonds with water molecules. Pentane is essentially immiscible.
(D) The large difference in the boiling points of alcohols and ethers is due to the presence of hydrogen bonding in alcohols. — True. Alcohol molecules are held together by intermolecular hydrogen bonds, which must be broken on boiling; ether molecules have no such bonds between them.
NCERT (2026-27 edition):
7.6.2 Physical Properties – “The C-O bonds in ethers are polar and thus, ethers have a net dipole moment. The weak polarity of ethers do not appreciably affect their boiling points which are comparable to those of the alkanes of comparable molecular masses but are much lower than the boiling points of alcohols as shown in the following cases:”
| Formula | CH3(CH2)3CH3 | C2H5-O-C2H5 | CH3(CH2)3-OH |
|---|---|---|---|
| n-Pentane | Ethoxyethane | Butan-1-ol | |
| b.p./K | 309.1 | 307.6 | 390 |
“The large difference in boiling points of alcohols and ethers is due to the presence of hydrogen bonding in alcohols.”
“The miscibility of ethers with water resembles those of alcohols of the same molecular mass. Both ethoxyethane and butan-1-ol are miscible to almost the same extent i.e., 7.5 and 9 g per 100 mL water, respectively while pentane is essentially immiscible with water. … This is due to the fact that just like alcohols, oxygen of ether can also form hydrogen bonds with water molecule …”