Reaction between marquis reagent and ibuprofen?

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In summary, the conversation discusses the reaction between Marquis reagent and ibuprofen, as well as the different color changes observed with ibuprofen and paracetamol. There is uncertainty about the specific mechanism of the reaction and why ibuprofen may give a color change while paracetamol does not. The possibility of different formulations or poorly characterized Marquis reagents is also mentioned.
  • #1
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Hello there good people,

I would like to know what is the product of the reaction between marquis reagent and ibuprofen?

CH2O is Formaldehyde, SO4 is Sulfuric Acid and C13H1802 is ibuprofen

The reaction is CH2O + SO4 + C13H1802 = ??

I was wondering what this equals and why ibuprofen gives a colour change of orange to brown but paracetamol does not when reacting with Marquis?
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  • #2
This is a valid question.

FWIW in US name for paracetamol==acetaminophen (Tylenol). I do not know a good answer, the molecules of both pain killers are different. What I can find on a search: Ibuprofen can affect renal function on overdose, acetaminophen damages liver tissues on overdose. There are Marquis color chart results for both, I believe, because for both illegal and legal drugs the Marquis test result has some legal standing.

@TeethWhitener @chemisttree

pinging two members who may know about how the reactions proceed.

Plus formulations of ibuprofen may possibly be the sodium salt. Which affects your question.
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I’m under the impression that most Marquis reagent products are poorly characterized, since the reaction conditions are pretty harsh. It apparently involves acylation and possibly polymerization/condensation of multiple molecules, and the final color will be determined by the electronic structure of whatever weird highly conjugated molecule is left at the end of the reaction.

That said, it’s not immediately clear to me why, if aromatic substitution is the main mechanism, paracetamol wouldn’t react but ibuprofen would. They both have an aromatic core with para pendant groups that are pretty strongly activating. Maybe someone else has a better answer.
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