If x and y are the pKb values of N-methylaniline and N,N-dimethylaniline respectively, what is the relation between x and y?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → x > y
pKb measures basic strength: the smaller the pKb, the stronger the base. The measured pKb values in water are compared:
Aniline (benzenamine): pKb = 9.38.
N-Methylaniline (one methyl on N): x = 9.30.
N,N-Dimethylaniline (two methyls on N): y = 8.92.
Comparison: 9.30 > 8.92, so x > y; neither value equals 9.38, and N,N-dimethylaniline is the stronger base of the two.
NCERT (2026-27 edition):
9.6 Chemical Reactions – “… Larger the value of Kb or smaller the value of pKb, stronger is the base. The pKb values of few amines are given in Table 9.3.”
Table 9.3: pKb Values of Amines in Aqueous Phase
