Why are amines soluble in water?
Consider the amine functionality: this is an electronegative site capable of binding to the electropositive sites of the water molecule.
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.
Of course, as physical scientists, we should seek actual data that inform our argument. This site gives a reasonable treatment.