a) Account for the following:
i) pK_b for aniline is more than that of methylamine.
ii) Aniline does not undergo Friedel–Crafts reactions.
iii) Primary amines have higher boiling points than tertiary amines.
i) pK_b for aniline is more than that of methylamine.
ii) Aniline does not undergo Friedel–Crafts reactions.
iii) Primary amines have higher boiling points than tertiary amines.
Solution
(i) Aniline's lone pair is shared with the ring; protonation sacrifices resonance — weaker base, larger pK.
(ii) Aniline's nitrogen donates its lone pair to AlCl; the resulting positively charged adduct deactivates the ring toward electrophiles.
(iii) Primary amines associate through N–H···N hydrogen bonds; tertiary amines cannot.
(ii) Aniline's nitrogen donates its lone pair to AlCl; the resulting positively charged adduct deactivates the ring toward electrophiles.
(iii) Primary amines associate through N–H···N hydrogen bonds; tertiary amines cannot.
CBSE Class 12 Board · 2022 · Subjective