Question

Why is the C – O – H bond angle in alcohols slightly less than the tetrahedral angle whereas the C – O – C bond angle in ether is slightly greater?

Answer 1

The C – O – H bond angle in alcohols is slightly less than the tetrahedral angle (109.5°) because of larger repulsions between the lone pairs of electrons. For example in methanol C – O – H bond angle is 108.9°.

In ethers, the C – O – C bond angle is slightly greater than tetrahedral angle. For example in dimethyl ether C – O – C bond angle is 111.7°. The larger bond angle in ethers may be because of greater repulsions between bulkier alkyl groups as compared to one H in alcohols.