Hippuric acid

Hippuric acid
IUPAC name	Benzoylaminoacetic acid
Other names	Hippuric acid, N-benzoylglycine, benzoyl glycocoll, benzoyl amidoacetic acid
Identifiers
CAS number	[495-69-2]
PubChem	464
SMILES	O=C(O)CNC(C1=CC=CC=C1)=O
Properties
Molecular formula	C9H9NO3
Molar mass	179.17 g/mol
Melting point	187 - 188 °C
Boiling point	240 °C (dec.)
Hazards
MSDS	MSDS from Oxford University
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) 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 can also indicate a toluene intoxication. 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:^[1]

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 azoimide.

History

Justus von Liebig showed in 1829 that hippuric acid differed from benzoic acid, and in 1839 determined its constitution, while in 1873 Victor Dessaignes synthesized it by the action of benzoyl chloride on the zinc salt of glycine.^[2] It was also formed by heating benzoic anhydride with glycine, ^[3] and by heating benzamide with monochloroacetic acid.

See also

• Aminohippuric acid

References

1. ^ A. W. Ingersoll and S. H. Babcock. "Hippuric acid". Org. Synth.; Coll. Vol. 2: 0328. 
2. ^ Dessaignes V. (1853). "Ueber die Regeneration der Hippursäure". Annalen der Chemie und Pharmacie 87 (3): 325–327. doi:10.1002/jlac.18530870311. 
3. ^ Curtius T. (1884). "Synthese von Hippursäure und Hippursäureäthern". Berichte der deutschen chemischen Gesellschaft 17 (2): 1662–1663. doi:10.1002/cber.18840170225. 

• This article incorporates text from the Encyclopædia Britannica, Eleventh Edition, a publication now in the public domain.