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Gentisic acid

Names
Preferred IUPAC name 2,5-Dihydroxybenzoic acid
Other names DHB 5-Hydroxysalicylic acid Gentianic acid Carboxyhydroquinone 2,5-Dioxybenzoic Acid Hydroquinonecarboxylic acid
Identifiers
CAS Number	490-79-9
3D model (JSmol)	Interactive image
ChEBI	CHEBI:17189
ChEMBL	ChEMBL1461
ChemSpider	3350
ECHA InfoCard	100.007.017
KEGG	C00628
PubChem CID	3469
UNII	VP36V95O3T
CompTox Dashboard (EPA)	DTXSID4060078
InChI InChI=1S/C7H6O4/c8-4-1-2-6(9)5(3-4)7(10)11/h1-3,8-9H,(H,10,11)Key: WXTMDXOMEHJXQO-UHFFFAOYSA-N InChI=1/C7H6O4/c8-4-1-2-6(9)5(3-4)7(10)11/h1-3,8-9H,(H,10,11)Key: WXTMDXOMEHJXQO-UHFFFAOYAO
SMILES O=C(O)c1cc(O)ccc1O
Properties
Chemical formula	C7H6O4
Molar mass	154.12 g/mol
Appearance	white to yellow powder
Melting point	204 °C (399 °F; 477 K)
Acidity (pKa)	2.97
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Y verify (what is  ?) Infobox references

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.

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

Production

Gentisic acid is produced by carboxylation of hydroquinone.

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.

Reactions

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

2,5-dihydroxybenzoate + O₂ ${\displaystyle \rightleftharpoons }$ 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, and has been shown to conveniently detect peptides incorporating the boronic acid moiety by MALDI.

References

1. Gentisic acid - Compound Summary, PubChem.
2. Haynes, p. 5.91
3. Haynes, p. 3.190
4. Levy, G; Tsuchiya, T (1972-08-31). "Salicylate accumulation kinetics in man". New England Journal of Medicine. 287 (9): 430–2. doi:10.1056/NEJM197208312870903. PMID 5044917.
5. Tian, Rong-Rong; Pan, Qiu-Hong; Zhan, Ji-Cheng; Li, Jing-Ming; Wan, Si-Bao; Zhang, Qing-Hua; Huang, Wei-Dong (2009). "Comparison of Phenolic Acids and Flavan-3-ols During Wine Fermentation of Grapes with Different Harvest Times". Molecules. 14 (2): 827–838. doi:10.3390/molecules14020827. PMC 6253884.
6. Hudnall, Phillip M. (2005) "Hydroquinone" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. Wiley-VCH, Weinheim. doi:10.1002/14356007.a13_499.
7. Behrman, E.J. (1988). Organic Reactions, Volume 35. New York: John Wiley & Sons Inc. p. 440. ISBN 978-0471832539.
8. Schock, R. U. Jr.; Tabern, D. L. (1951). "The Persulfate Oxidation of Salicylic Acid. 2,3,5-Trihydroxybenzoic Acid". The Journal of Organic Chemistry. 16 (11): 1772–1775. doi:10.1021/jo50005a018.
9. Strupat K, Karas M, Hillenkamp F (1991). "2,5-Dihidroxybenzoic acid: a new matrix for laser desorption-ionization mass spectrometry". Int. J. Mass Spectrom. Ion Process. 72 (111): 89–102. Bibcode:1991IJMSI.111...89S. doi:10.1016/0168-1176(91)85050-V.
10. Crumpton, J.; Zhang, W.; Santos, W. L. (2011). "Facile Analysis and Sequencing of Linear and Branched Peptide Boronic Acids by MALDI Mass Spectrometry". Analytical Chemistry. 83 (9): 3548–3554. doi:10.1021/ac2002565. PMC 3090651. PMID 21449540.

Cited sources

• Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press. ISBN 9781498754293.

• Hydroquinones
• Salicylic acids
• Dihydroxybenzoic acids
• Phenolic human metabolites
• Human drug metabolites