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I am trying to figure out the chemical formula for the reaction between Allura Red AC and $\ce{NaClO}$ (bleach). I have never met such reactions before in my study, and I was unable or maybe looked in the wrong places, to find the chemical equation for the reaction. The closest thing I have found is an image with the reaction but without the chemical equation. Could somebody please help me figure out the chemical equation for the reaction in the image?

Reaction depiction

Thanks for the help in advance.

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  • $\begingroup$ The structure of Allura Red AC appears to be incorrect. The methyl group should be para to the methoxy group in the benzene ring. $\endgroup$
    – user55119
    Aug 9, 2022 at 13:56
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    $\begingroup$ And the products are a problem. The nitrogen atoms are each missing a valence, and filling this in with a hydrogen atom is not consistent with an oxidation reaction. $\endgroup$ Aug 9, 2022 at 14:57

2 Answers 2

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@Maurice has pointed out the shortcomings of the proposed colorless products from the NaOCl oxidation of Allura Red AC (1, including the red atoms). A study has been reported[1] on the kinetics of the oxidation of Sunset Yellow (1, without the red atoms) with stoichiometric Chloramine-T (sodium N-chloro-4-methylbenzenesulfonamide) in alkali in the presence of catalytic Os(VIII). The structural similarities of the two dyes suggest that the products of oxidation are similar in the two cases. The authors were able to identify, after acidification, the sulfonic acid of o-naphthoquinone 3, benzenesulfonic acid 5 and nitrogen. The products from the oxidation would be expected to be the "red" analog of 5 and o-naphthoquinone 3.

The decomposition of 2 is effected by alkaline hydrolysis and elimination of the chlorohydrazone functionality. The authors propose a similar mechanism but they do not invoke a role for Os(VIII). It is likely that in their case, Os(VIII) is the oxidant and Chloramine-T is the regenerative reagent. Nonetheless, the Chloramine-T mechanism would apply to NaOCl. The OP's post claims that the products of oxidation are colorless. o-Naphthoquinone is yellow.


  1. K. N. Vinod, Puttaswamy and K. N. Ninge Gowda, Inorganic Chimica Acta, 2009, 362, 2044.
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The two molecules created by breaking the $\ce{N=N}$ bond have something wrong. They both have a final bond $\ce{-N-OH}$. This is impossible. It may be at least $\ce{-NH-OH}$. Maybe the $\ce{N2}$ group is removed, and a phenol or naphthol group is formed.

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