Consider the following nitrogenous bases: Aniline, Ammonia, Methylamine, and Dimethylamine. Which of the following represents the correct decreasing order of their p K_b values in aqueous solution?

Step-by-step solution

The basic strength of amines depends on the availability of the lone pair on the nitrogen atom for protonation. In aqueous solution, aliphatic amines are stronger bases than ammonia due to the + I effect of alkyl groups. Among methylamines, dimethylamine is a stronger base than methylamine due to a combination of + I effect, solvation, and steric factors. Aniline is a weaker base than ammonia because the lone pair on nitrogen is delocalised into the benzene ring through resonance. Thus, the decreasing order of basi