Arrange the following three compounds in order of decreasing acidity

B > A > C

The correct answer is option 1. B > A > C.

The given compounds are:

Let us explain the acidity trend:

In the context of comparing the acidity of amines, we need to focus on the stability of the conjugate bases formed after the donation of a proton. Compounds with more stable conjugate bases are generally more acidic.

A. Phenylammonium: It has no substituents attached to the phenyl group. The positive charge on the nitrogen is delocalized over the phenyl ring, providing some stability to the conjugate base.

B. p-Nitrophenylammonium: The nitro group (\(NO_2\)) is electron-withdrawing due to its strong -I effect and moderately strong -M effect. This electron withdrawal enhances the positive charge on the nitrogen, stabilizing the conjugate base through resonance.

C. p-Methylphenylammonium: The methyl group (\(CH_3\)) is weakly electron-donating due to its +I effect. It disperses electron density into the phenyl ring, making the positive charge on the nitrogen less stable and thus decreasing the acidity compared to the unsubstituted phenylammonium.

So, considering these factors, the correct order of decreasing acidity is 1. B > A > C

Therefore, the correct option is: 1. B > A > C