Arrange the following:
In increasing order of solubility in water: C6H5NH2, (C2H5)2NH, C2H5NH2.
The more extensive the H−bonding, the higher is the solubility. C2H5NH2 contains two H-atoms whereas (C2H5)2NH contains only one H-atom. Thus, C2H5NH2 undergoes more extensive H−bonding than (C2H5)2NH. Hence, the solubility in water of C2H5NH2 is more than that of (C2H5)2NH.
Further, the solubility of amines decreases with increase in the molecular mass. This is because the molecular mass of amines increases with an increase in the size of the hydrophobic part. The molecular mass of C6H5NH2 is greater than that of C2H5NH2 and (C2H5)2NH.
Hence, the increasing order of their solubility in water is as follows: C6H5NH2 < (C2H5)2NH < C2H5NH2