The correct statement regarding the basicity of arylamines is
A. Arylamines are generally more basic than alkylamines because of aryl group.
B. Arylamines are generally more basic than alkylamines because the nitrogen atom in arylamines is sp hybridised.
C. Arylamines are generally less basic than alkylamines because the lone pair of electrons of nitrogen are delocalised by interaction with the π electrons of the aromatic ring.
D. Arylamines are generally more basic than alkylamines because the lone pair of electron of nitrogen are not delocalised by interaction with the π electrons of aromatic ring.
E. Arylamines are generally weaker bases than alkylamines due to electron withdrawing nature shown by aryl group.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → C and E only
The basic strength of an amine is the readiness of the lone pair on nitrogen to accept a proton. In an arylamine such as aniline the N atom is attached directly to the benzene ring; its lone pair is in conjugation with the ring and is spread over it by resonance, so it is less available for protonation. Aniline has five resonance structures, while the anilinium ion has only two, so protonation costs resonance stabilisation. The aryl group also withdraws electrons from nitrogen. Alkyl groups do the opposite: they release electrons (+I) towards nitrogen. So arylamines are weaker bases than alkylamines (pKb of aniline 9.38, of methanamine 3.38).
(A) Arylamines are generally more basic than alkylamines because of aryl group. — Incorrect. The aryl group lowers basicity; arylamines are less basic.
(B) Arylamines are generally more basic than alkylamines because the nitrogen atom in arylamines is sp hybridised. — Incorrect. Arylamines are less basic, and the nitrogen of aniline is not sp hybridised; its lone pair is conjugated with the ring.
(C) Arylamines are generally less basic than alkylamines because the lone pair of electrons of nitrogen are delocalised by interaction with the π electrons of the aromatic ring. — Correct. This resonance makes the lone pair less available to a proton.
(D) Arylamines are generally more basic than alkylamines because the lone pair of electron of nitrogen are not delocalised by interaction with the π electrons of aromatic ring. — Incorrect. The lone pair is delocalised, and arylamines are less basic.
(E) Arylamines are generally weaker bases than alkylamines due to electron withdrawing nature shown by aryl group. — Correct. The aryl group draws electron density away from nitrogen, which lowers its basicity.
NCERT (2026-27 edition):
Basic Character of Amines – “… pKb value of aniline is quite high. … It is because in aniline or other arylamines, the -NH2 group is attached directly to the benzene ring. It results in the unshared electron pair on nitrogen atom to be in conjugation with the benzene ring and thus making it less available for protonation.”