The correct increasing order of basic strength of amine is:

(A) \(C_6H_5NH_2 < NH_3 < C_6H_5CH_2NH_2 < C_2H_5NH_2 < (C_2H_5)_2NH\)

(B) \(NH_3 < C_6H_5NH_2 < C_6H_5CH_2NH_2 < C_2H_5NH_2 < (C_2H_5)_2NH\)

(C) \(C_6H_5CH_2NH_2 < C_6H_5NH_2 < NH_3 < C_2H_5NH_2 < (C_2H_5)_2NH\)

(D) \(C_2H_5NH_2 < (C_2H_5)_2NH < C_6H_5NH_2 < NH_3\)

Choose the correct answer from the options given below:

(A) only

The correct answer is option 1. (A) only.

In organic chemistry, the basicity of amines depends on several factors:

Electron-donating groups: Amino groups (\(NH_2\)) are electron-donating groups. Aromatic amines like aniline (\(C_6H_5NH_2\)) have an amino group directly attached to a benzene ring. The benzene ring is electron-withdrawing due to its delocalized \(\pi\)-electrons. However, the amino group in \(C_6H_5NH_2\) still donates electrons, making it less basic than ammonia (\(NH_3\)), which doesn't have an electron-withdrawing group attached.

Resonance stabilization: The lone pair of electrons on the nitrogen in aniline can delocalize into the benzene ring via resonance, reducing the availability of the lone pair for accepting a proton. This resonance stabilization decreases the basicity of \(C_6H_5NH_2\) compared to \(NH_3\).

Inductive effect: Alkyl groups (\(C_2H_5\) and \((C_2H_5)_2\)) can donate electrons through the sigma bonds, thus increasing the electron density on the nitrogen atom, which increases basicity.

Considering these factors, the correct order of increasing basicity among the given amines is:

\(C_6H_5NH_2 < NH_3 < C_6H_5CH_2NH_2 < C_2H_5NH_2 < (C_2H_5)_2NH\)

Here's why:

\(C_6H_5NH_2\) is less basic than \(NH_3\) due to resonance stabilization from the aromatic ring

\(C_6H_5CH_2NH_2\) is less basic than \(C_6H_5NH_2\) due to the presence of an alkyl group, which increases electron density on the nitrogen atom.

\(C_2H_5NH_2\) is less basic than \(C_6H_5CH_2NH_2\) due to the presence of two alkyl groups, further increasing electron density on the nitrogen atom.

\((C_2H_5)_2NH\) is the most basic due to the presence of two ethyl groups, which strongly increase electron density on the nitrogen atom.

Therefore, option (A) correctly reflects the increasing order of basic strength among the given amines.