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Reaction between Aniline yellow and HCL

What is the chemical reaction between Aniline yellow ( 4-Aminoazobenzene or p-Aminoazobenzene) and HCL that changes the aniline yellow color to red?

If NaOH is then added why does it turn to yellow?
Original post by Xoder
What is the chemical reaction between Aniline yellow ( 4-Aminoazobenzene or p-Aminoazobenzene) and HCL that changes the aniline yellow color to red?

If NaOH is then added why does it turn to yellow?


When the lone pair on the nitrogen is protonated, it cannot take part in conjugation, so the structure of the chromophore absorbs visible light of different wavelength.

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