Hippuric acid

Hippuric acid

Names
IUPAC name Benzoylaminoethanoic acid
Other names Hippuric acid, N-benzoylglycine, benzoyl glycocoll, benzoyl amidoacetic acid
Identifiers
CAS Number	495-69-2
3D model (Jmol)	Interactive image
ChEBI	CHEBI:18089
ChEMBL	ChEMBL461
ChemSpider	451
ECHA InfoCard	100.007.098
KEGG	C01586
PubChem	464
UNII	TE0865N2ET
InChI InChI=1S/C9H9NO3/c11-8(12)6-10-9(13)7-4-2-1-3-5-7/h1-5H,6H2,(H,10,13)(H,11,12) Key: QIAFMBKCNZACKA-UHFFFAOYSA-N InChI=1/C9H9NO3/c11-8(12)6-10-9(13)7-4-2-1-3-5-7/h1-5H,6H2,(H,10,13)(H,11,12) Key: QIAFMBKCNZACKA-UHFFFAOYAD
SMILES c1ccc(cc1)C(=O)NCC(=O)O
Properties
Chemical formula	C9H9NO3
Molar mass	179.17 g/mol
Density	1,371 g/cm^3
Melting point	187 to 188 °C (369 to 370 °F; 460 to 461 K)
Boiling point	240 °C (464 °F; 513 K) (decomposes)
Hazards
Safety data sheet	Material Safety Data Sheet
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

Hippuric acid (Gr. hippos, horse, ouron, urine) is a carboxylic acid found in the urine of horses and other herbivores. Hippuric acid crystallizes in rhombic prisms which are readily soluble in hot water, melt at 187 °C, and decompose at about 240 °C. High concentrations of hippuric acid may also indicate a toluene intoxication; however, scientists have called this correlation into question because there are other variables that influence levels of hippuric acid.^[1] When many aromatic compounds such as benzoic acid and toluene are taken internally, they are converted to hippuric acid by reaction with the amino acid, glycine.

Synthesis

A modern synthesis of hippuric acid involves the acylation of glycine with benzoyl chloride:^[2]

Reactions

Hippuric acid is readily hydrolysed by hot caustic alkalis to benzoic acid and glycine. Nitrous acid converts it into benzoyl glycolic acid, C₆H₅C(=O)OCH₂CO₂H. Its ethyl ester reacts with hydrazine to form hippuryl hydrazine, C₆H₅CONHCH₂CONHNH₂, which was used by Theodor Curtius for the preparation of hydrazoic acid.

History

Justus von Liebig showed in 1829 that hippuric acid differed from benzoic acid,^[3] and in 1834 determined its constitution,^[4] while in 1853 French chemist Victor Dessaignes (1800–1885) synthesized it by the action of benzoyl chloride on the zinc salt of glycine.^[5] It was also formed by heating benzoic anhydride with glycine,^[6] and by heating benzamide with monochloroacetic acid.

See also

• Aminohippuric acid
• Ortho-iodohippurate

References

1. Pero, RW (2010). "Health consequences of catabolic synthesis of hippuric acid in humans". Current clinical pharmacology. 5 (1): 67–73. doi:10.2174/157488410790410588. PMID 19891605.
2. A. W. Ingersoll and S. H. Babcock. "Hippuric acid". Org. Synth.; Coll. Vol., 2, p. 0328
3. Liebig, Justus (1829) "Ueber die Säure, welche in dem Harn der grasfressenden vierfüssigen Thiere enthalten ist" (On the acid which is contained in the urine of grass-eating, four-footed animals), Annalen der Physik und Chemie, 17 : 389–399.
4. Liebig, Justus (1834) "Ueber die Zusammensetzung der Hippursäure" (On the composition of hippuric acid), Annalen der Physik und Chemie, 32 : 573–574.
5. Dessaignes V. (1853). "Ueber die Regeneration der Hippursäure" [On the regeneration of hippuric acid]. Annalen der Chemie und Pharmacie. 87 (3): 325–327. doi:10.1002/jlac.18530870311. See also: Dessaignes (1853) "Note sur la régénération de l'acide hipparique," Comptes rendus, 37 : 251–252.
6. Curtius T. (1884). "Synthese von Hippursäure und Hippursäureäthern" [Synthesis of hippuric acid and hippuric acid esters]. Berichte der deutschen chemischen Gesellschaft. 17 (2): 1662–1663. doi:10.1002/cber.18840170225.

•  This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Hippuric Acid". Encyclopædia Britannica (11th ed.). Cambridge University Press.