Right now I'm trying to explain why the ink from an ink pen turns colourless in water.

I know that the pH is responsible as it breaks apart the conjugated system of double bonds. I'm just not sure on which part, to $\ce{OH-}$ comes into play (example: Water blue).

My suggestion would be that $\ce{OH-}$ can be reversible added to double bond in the center forming two phenyl rings and one ring with 2 double bonds (which will rearrange into a phenyl ring with the double bond from the following amide-group) with a $\ce{C-OH}$ in between.

Under acetic conditions, the $\ce{OH-}$ is eliminated.

Is that correct and does anyone know a mechanism, explanation etc. for that reaction somewhere on the Internet?


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