Arrange the following:

(i) In increasing order of their basic strength

C₆H₅-NH₂, CH₃-CH₂-NH₂, CH₃-NH-CH₃

(ii) In increasing order of solubility in water

CH₃-NH₂, (CH₃)₃N, CH₃-NH-CH₃

Increasing order of basicity,

• We know that basic nature of amine follows the trend 3°<2°<1°.

• But in the presence of a bulky group such as benzene ring, there will be steric hindrance which will result in the decrease in the basicity of the group.

• Thus, the order of increasing basicity for the above compounds is,

CH₃-NH-CH₃>CH₃-CH₂-NH₂>C₆H₅-NH₂.

Increasing order of solubility in water,

• If the alkyl group is small, there will be no steric hindrance against Hydrogen bonding with water.

• The trend followed then will be 2°>1°>3°.

• Thus, the order of increasing solubility for the above compounds is,

(CH₃)₂NH>CH₃NH₂>(CH₃)₃N.