Arrange the following in increasing order of their basic strength: (i) `C_(2)H_(5)NH_(2),C_(6)H_(5)NH_(2),NH_(3),C_(6)H_(5)CH_(2)NH_(2)and(C_(2)H_(5))

(i) Considering the inductive effect of alkyl groups, `NH_(3),H_(5)NH_(2)and (C_(2)H_(5))_(2)NH` can be arranged in the increasing order of their basic strengths as:
`NH_(3) ltC_(2)H_(5)NH_(2)lt(C_(2)H_(5))_(2)NH`
Due to the - I effect of `C_(6)H_(5)` group, the electron density on the N-atom in `C_(6)H_(5)CH_(2)NH_(2)` is lower than that on the N- atom in `C_(2)H_(5)NH_(2)` but morre than that in `NH_(3)` Therefore, the goven compounds can be arranged in the order of their basic strengths as:
`C_(6)H_(5)NH_(2) ltNH_(3)ltC_(6)H_(5)CH_(2)NH_(2)ltC_(2)H_(5)NH_(2)lt(C_(2)H_(5))_(2)NH`
(ii) Considering the inductive effect and the steric hidrance of the alkyl groups, `C_(2)H_(5)NH_(2),(C_(2)H_(5))_(2)NH_(2),`and their basic strengths as follows:
`C_(2)H_(5)NH_(2)lt(C_(2)H_(5))_(3)Nlt(C_(2)H_(5))_(2)NH`
Again, due to the - R effect of `C_(6)H_(5)` group, the electron density on the n atom in `C_(6)H_(5)NH_(2)` is lower than that on the N atom in `C_(2)H_(5NH_(2).` Therefore, the basicity of `C_(6)H_(5)NH_(2)` is lower than that of `C_(2)H_(5)NH_(2).` Hence, the given compounds can be arranged in the increasing order of their basic strengths as follows :
`C_(6)H_(5)NH_(2)ltC_(2)H_(5)NH_(2)lt(C_(2)H_(5))_(3)Nlt(C_(2)H_(5))NH`
(iii) Considering the inductive effect and the steric hindrance of alkyl groups, `CH_(3)NH_(2),(CH_(3))_(2)NH,` and `(CH_(3))_(3)N` can be arranged in the increasing order of their basic strengths as :
`(CH_(3))_(3)NltCH_(3)NH_(2)lt(CH_(3))_(2)NH`
In `C_(6H_(5NH_(2),` N is directly attached to the benzene ring. Thus, the lone pair of electrons on the N−atom is delocalized over the benzene ring. In `C_(6)H_(5)CH_(2)NH_(2),` N is not directly attached to the benzene ring. Thus, its lone pair is not delocalized over the benzene ring. Therefore, the electrons on the N atom are more easily available for protona in `C_(6)H_(5)CH_(2)NH_(2)` than in `C_(6)H_(5)NH_(2)` i.e., `C_(6)H_(5)CH_(2)NH_(2)` is more basic than `C_(6)H_(5)NH_(2).` Aggin, due to t he -I effect of `C_(6)H_(5)` group, the electron density on the N-atom in `C_(6)H_(5)CH_(2)NH_(2)` is lower than that on the N-atom in `(CH_(3))_(3)N.` Therefore, `(CH_(3))_(3)N` more basic than `C_(6)H_(5)CH_(2)NH_(2).` Thus, the given compounds can be arranged in the increasing order of their basic strengths as follows.
`C_(6)H_(5)NH_(2) lt C_(6)H_(5)CH_(2)NH_(2) lt(CH_(3))_(3)N ltCH_(3)NH_(2) lt(CH_(3))_(2)NH`