Question

Why are amines soluble in water?

Answer 1

Consider the amine functionality: this is an electronegative site capable of binding to the electropositive sites of the water molecule.

Explanation:

The nitrogen centre is of course a basic site, which possesses a formal lone pair. Primary amines should have considerable solubility in water on this basis. As the hydrocarbyl chain grows longer, and hydrocarbyl substitution increases (i.e. `1""^@` to `2""^@` to `3""^@`, basicity should increase but water solubility should decrease inasmuch as carbon chain-carbon chain interactions should become more significant and stronger).

Of course, as physical scientists, we should seek actual data that inform our argument. This site gives a reasonable treatment.