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]
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]
^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)
^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. ISBN978-3-527-31801-8.{{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.