Explain the following observations:
i) In aqueous solution the K_b order is Et₂NH > Et₃N > EtNH₂.
ii) Amines are more basic than comparable alcohols.
i) In aqueous solution the K_b order is Et₂NH > Et₃N > EtNH₂.
ii) Amines are more basic than comparable alcohols.
Solution
(i) More ethyls push more density (+I), but each N–H lost means poorer hydration/stabilisation of the cation. The opposing trends peak at the secondary amine:
(ii) Nitrogen, less electronegative than oxygen, holds its lone pair more loosely and accommodates the positive charge of R–NH better than oxygen does R–OH — so amines ≫ alcohols as bases.
(ii) Nitrogen, less electronegative than oxygen, holds its lone pair more loosely and accommodates the positive charge of R–NH better than oxygen does R–OH — so amines ≫ alcohols as bases.
CBSE Class 12 Board · 2004 · All India · Subjective