pKb values of amines in waterजल में ऐमीनों के pKb मानpKb values of amines in water

NCERT Table 9.3 · Class 12 Chemistry · Chapter 9 · interactive diagram

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Parts and what they mean

Ammonia: pKb 4.75 (dashed line) (अमोनिया: pKb 4.75 (डैश रेखा)) — Reference line. Bars shorter than it → stronger bases than NH₃ (aliphatic amines); longer → weaker (aromatic amines).
Methanamine, CH₃NH₂: 3.38 (मेथेनेमीन, CH₃NH₂: 3.38) — Stronger base than NH₃ (+I effect of CH₃).
N-Methylmethanamine, (CH₃)₂NH: 3.27 (N-मेथिलमेथेनेमीन, (CH₃)₂NH: 3.27) — Strongest of the methyl series in water: (CH₃)₂NH > CH₃NH₂ > (CH₃)₃N > NH₃.
N,N-Dimethylmethanamine, (CH₃)₃N: 4.22 (N,N-डाइमेथिलमेथेनेमीन, (CH₃)₃N: 4.22) — Weaker than the 1° and 2° methylamines in water: its cation (CH₃)₃NH⁺ has only one N–H, so it is least stabilised by H-bonding with water.
Ethanamine, C₂H₅NH₂: 3.29 (एथेनेमीन, C₂H₅NH₂: 3.29) — Ethyl series in water: (C₂H₅)₂NH > (C₂H₅)₃N > C₂H₅NH₂ > NH₃.
N-Ethylethanamine, (C₂H₅)₂NH: 3.00 (N-एथिलएथेनेमीन, (C₂H₅)₂NH: 3.00) — The strongest base in this table (smallest pKb).
N,N-Diethylethanamine, (C₂H₅)₃N: 3.25 (N,N-डाइएथिलएथेनेमीन, (C₂H₅)₃N: 3.25) — With bigger ethyl groups the order changes: here 3° is stronger than 1° (interplay of +I, solvation and steric hindrance).
Phenylmethanamine (benzylamine), C₆H₅CH₂NH₂: 4.70 (फ़ेनिलमेथेनेमीन (बेन्ज़िलऐमीन), C₆H₅CH₂NH₂: 4.70) — The –NH₂ is on a CH₂, not on the ring, so its lone pair is not delocalised: it behaves like an aliphatic amine and is far more basic than aniline.
Benzenamine (aniline): 9.38 (बेन्ज़ेनेमीन (ऐनिलीन): 9.38) — Very weak base: the N lone pair is in conjugation with the ring (5 resonance structures of aniline vs 2 of anilinium ion).
N-Methylaniline: 9.30 (N-मेथिलऐनिलीन: 9.30) — Aromatic amine — weaker base than ammonia.
N,N-Dimethylaniline: 8.92 (N,N-डाइमेथिलऐनिलीन: 8.92) — Still a much weaker base than ammonia.
pKb = −log Kb (pKb = −log Kb) — Larger Kb or smaller pKb → stronger base.

Original diagram drawn by Simple Learning Hub, based on NCERT Table 9.3. Report a mistake