Ans: Considering the inductive effect of alkyl groups $\mathrm{NH}_{3}, \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}$ and $\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH}$ can be arranged in the increasing order of their basic strengths as: $\mathrm{NH}_{3}<\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}<\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH}$ Again, $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}$ has proton acceptability less than $\mathrm{NH}_{3}$. Thus, we have: $$ \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}<\mathrm{NH}_{3}<\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{NH}_{2}<\left(\mathrm{C}_{2} \mathrm{H}_{3}\right)_{2} \mathrm{NH} $$ Due to the $-\mathrm{I}$ effect of $\mathrm{C}_{6} \mathrm{H}_{5}-$ group, the electron density on the $\mathrm{N}$-atom in $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{NH}_{2}$ is lower than that on the $\mathrm{N}$-atom in $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}$, but more than that in $\mathrm{NH}_{3}$. Therefore, the given compounds can be arranged in the order of their basic strengths as: Ans: Considering the inductive effect and the steric hindrance of the alkyl groups, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2} \quad\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH}$, and their basic strengths as follows: $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}<\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{3} \mathrm{~N}<\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH}$ Again, due to the $-\mathrm{R}$ effect of $\mathrm{C}_{6} \mathrm{H}_{5}-$ group, the electron density on the $\mathrm{N}$ atom in $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}$ is lower than that on the $\mathrm{N}$ atom in $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}$. Therefore, the basicity of $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}$ is lower than that of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}$. Hence, the given compounds can be arranged in the increasing order of their basic strengths as follows: $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}<\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}<\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{3} \mathrm{~N}<\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH}$ iii. $\mathrm{CH}_{3} \mathrm{NH}_{2},\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH},\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}, \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}, \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{NH}_{2}$ Ans: Considering the inductive effect and the steric hindrance of alkyl groups, $\mathrm{CH}_{3} \mathrm{NH}_{2},\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}$, and $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}$ can be arranged in the increasing order of their basic strengths as: $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}<\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}<\mathrm{CH}_{3} \mathrm{NH}_{2}$ In $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}$, Nitrogen is directly attached to the benzene ring. Thus, the lone pair of electrons on the $\mathrm{N}$-atom is delocalized over the benzene ring. In $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{NH}_{2}$, Nitrogen is not directly attached to the benzene ring. Thus, its lone pair is not delocalized over the benzene ring. Therefore, the electrons on the $\mathrm{N}$ atom are more easily available for protonation in $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{NH}_{2}$ than in $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}$ i.e., $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{NH}_{2}$ is more basic than $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}$. Again, due to the $-\mathrm{I}$ effect of $\mathrm{C} 6 \mathrm{H} 5$ group, the electron density on the $\mathrm{N}$-atom in $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{NH}_{2}$ is lower than that on the $\mathrm{N}$-atom in $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}$. Therefore, $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}$ is more basic than $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{NH}_{2}$. Thus, the given compounds can be arranged in the increasing order of their basic strengths as follows. $$ \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}<\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{NH}_{2}<\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}<\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}<\mathrm{CH}_{3} \mathrm{NH}_{2} $$