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Picolinic acid
Names
	Preferred IUPAC name Pyridine-2-carboxylic acid
	Other names Picolinic acid
Identifiers
CAS Number	98-98-6 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:28747 ;
ChEMBL	ChEMBL72628 ;
ChemSpider	993 ;
ECHA InfoCard	100.002.472
PubChem CID	1018;
UNII	QZV2W997JQ ;
CompTox Dashboard (EPA)	DTXSID7031903 ;
	InChI InChI=1S/C6H5NO2/c8-6(9)5-3-1-2-4-7-5/h1-4H,(H,8,9) Key: SIOXPEMLGUPBBT-UHFFFAOYSA-N ; InChI=1/C6H5NO2/c8-6(9)5-3-1-2-4-7-5/h1-4H,(H,8,9) Key: SIOXPEMLGUPBBT-UHFFFAOYAC;
	SMILES c1ccnc(c1)C(=O)O;
Properties
Chemical formula	C6H5NO2
Molar mass	123.111 g·mol−1
Appearance	White solid
Density	1.526 g/cm³
Melting point	136 to 138 °C (277 to 280 °F; 409 to 411 K)
Solubility in water	Slightly soluble (0.41%) in water
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Picolinic acid is an organic compound with the formula NC₅H₄CO₂H. It is a derivative of pyridine with a carboxylic acid (COOH) substituent at the 2-position. It is an isomer of nicotinic acid and isonicotinic acid, which have the carboxyl side chain at the 3- and 4-positions, respectively. It is a white solid although impure samples can appear tan. The compound is soluble in water.

Production

On a commercial scale, picolinic acid is produced by ammoxidation of 2-picoline followed by hydrolysis of the resulting nitrile:

NC₅H₄CH₃ + 1.5 O₂ + NH₃ → NC₅H₄C≡N + 3 H₂O

NC₅H₄C≡N + 2 H₂O → NC₅H₄CO₂H + NH₃

It is also produced by oxidation of picoline with nitric acid.^[2]

In the laboratory, picolinic acid is formed from 2-methylpyridine by oxidation with potassium permanganate (KMnO₄).^[3]^[4]

Reactions

Hydrogenation of picolinic acid gives piperidine-2-carboxylic acid, a precursor to the drug Mepivacaine.

Picolinic acid is a bidentate chelating agent of elements such as chromium, zinc, manganese, copper, iron, and molybdenum in the human body.^[5]^[6]

It is a substrate in the Mitsunobu reaction. In the Hammick reaction, picolinic acid reacts with ketones to give pyridine-2-carbonols:^[7]

NC₅H₄CO₂H + R₂C=O → NC₅H₄CR₂(OH) + CO₂

Biosynthesis

Picolinic acid is a catabolite of the amino acid tryptophan through the kynurenine pathway.^[8] Its function is unclear, but it has been implicated in a variety of neuroprotective, immunological, and anti-proliferative effects. In addition, it is suggested to assist in the absorption of zinc(II) ions and other divalent or trivalent ions through the small intestine.^[9]

Picolinates

Salts of picolinic acid (picolinates) include:

References

^ Lide, DR. "CRC Handbook of Chemistry and Physics, Internet Version 2005, http://hbcpnetbase.com, CRC Press, Boca Raton, Florida, 2005". {{cite journal}}: Cite journal requires |journal= (help); External link in |title= (help)
^ Shimizu, Shinkichi; Watanabe, Nanao; Kataoka, Toshiaki; Shoji, Takayuki; Abe, Nobuyuki; Morishita, Sinji; Ichimura, Hisao (2007). "Pyridine and Pyridine Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a22_399. ISBN 978-3527306732.
^ Singer, Alvin W.; McElvain, S. M. (1940). "Picolinic Acid Hydrochloride". Organic Syntheses. 20: 79. doi:10.15227/orgsyn.020.0079.
^ Harold Hart, Leslie E. Craine, David J. Hart, Christopher M. Hadad; Nicole Kindler (2007). 'Organische Chemie 3. Auflage. Weinheim: Wiley-VCH. p. 494. ISBN 978-3-527-31801-8.{{cite book}}: CS1 maint: multiple names: authors list (link)
^ Lumme, Paavo; Lundgren, Georg; Mark, Wanda; Lundström, Hans; Borch, Gunner; Craig, J. Cymerman (1969). "The Crystal Structure of Zinc Picolinate Tetrahydrate, Zn(C₆H₄O₂N)₂(H₂O)₄". Acta Chemica Scandinavica. 23: 3011–3022. doi:10.3891/acta.chem.scand.23-3011.
^ Daugulis, Olafs; Roane, James; Tran, Ly Dieu (2015). "Bidentate, Monoanionic Auxiliary-Directed Functionalization of Carbon–Hydrogen Bonds". Accounts of Chemical Research. 48 (4): 1053–1064. doi:10.1021/ar5004626. PMC 4406856. PMID 25756616.
^ Fuchs, Philip L. (29 July 2013). "Picolinic acid". Catalytic Oxidation Reagents. Wiley Inc. p. 495ff. ISBN 9781118704844. OCLC 954583821.
^ Tan, L.; et al. (December 2012). "The kynurenine pathway in neurodegenerative diseases: mechanistic and therapeutic considerations". J Neurol Sci. 323 (1–2): 1–8. doi:10.1016/j.jns.2012.08.005. PMID 22939820. S2CID 6061945.
^ Evans, Gary (1982). "The Role of Picolinic Acid in Metal Metabolism". Life Chemistry Reports. 1. Harwood Academic Publishers: 57–67. Archived from the original on 26 January 2016. Retrieved 20 March 2015.