Monoalkylamines with short-chain alkyl radicals are gases, Monoalkylamines with medium-length radicals (up to about 11 C atoms) are liquids, and the higher alkylamines are solids.
All amines have a characteristic odor, which in many alkylamines is reminiscent of ammonia.
The intensity of the odor declines as the molecular weight increases.
The dissolving properties follow a similar pattern: short-chain alkylamines are freely soluble in water and the common organic solvents such as ethanol or ether.
As the molecular weight and the degree of substitution increase, the solubility in water decreases.
Most aliphatic di- and triamines are faintly coloured, slightly viscous liquids that are freely soluble in water and have an intense ammonia-like odor. They have almost unlimited miscibility with methanol, acetone, toluene, and ether, but are only sparingly soluble in aliphatic hydrocarbons.