What are the physical properties of amines?

Lower aliphatic amines, such as methylamine and ethylamine, have a distinct fishy odor and exist in the gaseous state at room temperature. Aryl amines, like aniline, are usually colorless. However, they develop color upon exposure to air due to atmospheric oxidation. Primary amines containing 3-4 carbon atoms are typically liquid at room temperature, while those with more than four carbon atoms are solid. Amines with fewer than six carbon atoms are generally soluble in water due to hydrogen bonding between the amine nitrogen and water molecules. All types of amines—primary, secondary, and tertiary—have the ability to form hydrogen bonds with water molecules. However, as the carbon chain length increases, solubility decreases. Aromatic amines are less soluble in water compared to aliphatic amines. Lastly, as the molecular weight of amines increases, their boiling and melting points also increase due to stronger intermolecular forces. Thus, in terms of boiling points, the order of amines from highest to lowest is as follows: primary > secondary > tertiary.