Q6(f). UV absorption of aniline in neutral and in acidic solution
Aniline absorbs at 280 nm (εmax 8600), but in acidic solution, the main absorption band is observed at 203 nm (εmax 7500). Provide a suitable explanation. (Unit of εmax is M⁻¹ cm⁻¹)
Answer in brief
In acid aniline becomes the anilinium ion; the nitrogen lone pair is no longer conjugated with the ring, so the spectrum returns to that of benzene: blue shift and lower ε.
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CoversUV spectrum of anilineanilinium ionauxochromehypsochromic shiftn–π conjugation
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