Picolinic acid

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.

Picolinic acid

Names
Preferred IUPAC name Pyridine-2-carboxylic acid
Other names Picolinic acid
Identifiers
CAS Number	98-98-6 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:28747 Y
ChEMBL	ChEMBL72628 Y
ChemSpider	993 Y
ECHA InfoCard	100.002.472
PubChem CID	1018
UNII	QZV2W997JQ Y
CompTox Dashboard (EPA)	DTXSID7031903
InChI InChI=1S/C6H5NO2/c8-6(9)5-3-1-2-4-7-5/h1-4H,(H,8,9) Y Key: SIOXPEMLGUPBBT-UHFFFAOYSA-N Y 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[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

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

Structure of Zn(picolinate)₂(H₂O)₂.

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:

• Chromium(III) picolinate
• Zinc picolinate

See also

• Dipicolinic acid