Gentisic acid

Gentisic acid^[1]

Names
IUPAC name 2,5-dihydroxybenzoic acid
Other names DHB 2,5-dihydroxybenzoic acid 5-Hydroxysalicylic acid Gentianic acid Carboxyhydroquinone 2,5-Dioxybenzoic Acid Hydroquinonecarboxylic acid
Identifiers
CAS Number	490-79-9
ChEBI	CHEBI:17189
ChEMBL	ChEMBL1461
ChemSpider	3350
Jmol interactive 3D	Image
KEGG	C00628
PubChem	3469
UNII	VP36V95O3T
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	200 to 205 °C (392 to 401 °F; 473 to 478 K) (Sublimes)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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.^[2]

It is also found in the African tree Alchornea cordifolia and in wine.^[3]

Production

Gentisic acid is produced by carboxylation of hydroquinone.^[4]

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 (50% yield).^[5][6]

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, ^[7] and has been shown to conveniently detect peptides incorporating the boronic acid moiety by MALDI. ^[8]

References

1. Gentisic acid - Compound Summary, PubChem.
2. Levy, G; Tsuchiya, T (1972-09-31). "Salicylate accumulation kinetics in man". New England Journal of Medicine 287 (9): 430–2. doi:10.1056/NEJM197208312870903. PMID 5044917. Check date values in: |date= (help)
3. Comparison of Phenolic Acids and Flavan-3-ols During Wine Fermentation of Grapes with Different Harvest Times. Rong-Rong Tian, Qiu-Hong Pan, Ji-Cheng Zhan, Jing-Ming Li, Si-Bao Wan, Qing-Hua Zhang and Wei-Dong Huang, Molecules, 2009, 14, pages 827-838, doi:10.3390/molecules14020827
4. Phillip M. Hudnall "Hydroquinone" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. 2005 Wiley-VCH, Weinheim. doi:10.1002/14356007.a13_499.
5. Behrman, E.J. (1988). Organic Reactions, Volume 35. New York: John Wiley & Sons Inc. p. 440. ISBN 0471832537.
6. R. U. Schock Jr.; and D. L. Tabern (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.
7. 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 Processes 72 (111): 89–102. Bibcode:1991IJMSI.111...89S. doi:10.1016/0168-1176(91)85050-V.
8. 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.