Gentisic acid

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Gentisic acid[1]
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Molar mass 154.12 g/mol
Appearance white to yellow powder
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Acidity (pKa) 2.97[2]

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Gentisic acid is a dihydroxybenzoic acid. It is a derivative of benzoic acid and a minor (1%) product of the metabolic break down of aspirin, excreted by the kidneys.[3]

It is also found in the African tree Alchornea cordifolia and in wine.[4]

Production

Gentisic acid is produced by carboxylation of hydroquinone.[5]

C6H4(OH)2 + CO2 → C6H3(CO2H)(OH)2

This conversion is an example of a Kolbe–Schmitt reaction.

Alternatively the compound can be synthesized from salicylic acid via Elbs persulfate oxidation.[6][7]

Reactions

In the presence of the enzyme gentisate 1,2-dioxygenase, gentisic acid reacts with oxygen to give maleylpyruvate:

2,5-dihydroxybenzoate + O2 maleylpyruvate

Applications

As a hydroquinone, gentisic acid is readily oxidised and is used as an antioxidant excipient in some pharmaceutical preparations.

In the laboratory, it is used as a sample matrix in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry,[8] and has been shown to conveniently detect peptides incorporating the boronic acid moiety by MALDI.[9]

References

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  1. Gentisic acid - Compound Summary, PubChem.
  2. Haynes, p. 5.91
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  5. Hudnall, Phillip M. (2005) "Hydroquinone" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. Wiley-VCH, Weinheim. Script error: No such module "CS1 identifiers"..
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