JEE Main 2020 · 8 January · morning · Single correct · +4 / −1
The predominant intermolecular forces present in ethyl acetate, a liquid, are:
- (a) Dipole-dipole and hydrogen bonding
- (b) hydrogen bonding and London dispersion
- (c) London dispersion, dipole-dipole and hydrogen bonding
- (d) London dispersion and dipole-dipole
Answer and solution
Answer (d) London dispersion and dipole-dipole
Solution
Chemistry ma’am · 3 steps
Before you write hydrogen bonding, look for an H attached to O, N or F. Ethyl acetate has none.
- Look at the structure. Ethyl acetate is CH₃COOCH₂CH₃, an ester. Every hydrogen in it is bonded to carbon. It has a polar C=O group and a C-O-C link, but no O-H group.
Force What it needs In ethyl acetate? London dispersion Electrons in any molecule Yes, every molecule has it Dipole-dipole A permanent dipole moment Yes, the C=O bond is strongly polar Hydrogen bonding H bonded directly to O, N or F No, all H atoms sit on carbon - Why no H-bonding. The oxygen atoms could accept a hydrogen bond, but a hydrogen bond also needs a donor H. A C-H hydrogen is not positive enough to act as one, so ethyl acetate molecules cannot hydrogen bond with each other.
- So. Only London dispersion and dipole-dipole forces act between ethyl acetate molecules, which is option (d).
The idea to keep. Oxygen in a molecule is not enough for hydrogen bonding. You need an H sitting directly on O, N or F. Pure esters, ethers, ketones and aldehydes show only dipole-dipole and dispersion.
Answer from the NTA final answer key. Solution by PrepWiser.