Which of the following amines is not a gas?

Trimethylamine

The correct answer is option 1. Trimethylamine.

Among the listed amines, the one that is not a gas is: Trimethylamine.

As the number of carbon atoms in the alkyl chain attached to the nitrogen atom increases, the intermolecular forces between amine molecules become stronger. This is due to a combination of factors like van der Waals forces and London dispersion forces. Stronger intermolecular forces make it harder for the molecules to overcome the attractive forces and escape into the gas phase.

Methylamine, Ethylamine, and Dimethylamine are all relatively small molecules with weaker intermolecular forces compared to trimethylamine. This allows them to exist as gases at room temperature and pressure.

Trimethylamine, with three methyl groups attached to the nitrogen, has stronger London dispersion forces and can exist as a liquid at room temperature.