In aqueous solution 8-hydroxyquinoline has a pKa value of ca. 9.9[1] It reacts with metal ions, losing the proton and forming 8-hydroxyquinolinato-chelate complexes.
In its photo-induced excited-state, 8-hydroxyquinoline converts to zwitterionic isomers, in which the hydrogen atom is transferred from oxygen to nitrogen.[5]
History
8-hydroxyquinoline was first obtained by Hugo Weidel and his student Albert Cobenzl in 1880. They decarboxylated so-called oxycinchoninic acid (from cinchonine) and characterized the resulting compound as melting at about 70°C. They identified that the hydroxy group is on the benzene ring (but not its particular place) and called the compound oxyquinoline and α-quinophenol.[6]
In the following year more chemists found other ways to make the compound. Zdenko Hans Skraup discovered a way to synthesize substituted quinolines from substituted phenols and described three isomers of oxyquinoline, identifying the structure of 8-hydroxyquinoline.[7]Otto Fischer [de] and his student Karl Bedall made the compound from a sulphonic acid independently at about the same time, but misidentified its structure.[8][9]
The roots of the invasive plant Centaurea diffusa release 8-hydroxyquinoline, which has a negative effect on plants that have not co-evolved with it.[17]
See also
Nitroxoline (5-nitro-8-hydroxyquinoline), an antiprotozoal drug
^Albert, A.; Phillips, J. N. (1956). "264. Ionization Constants of Heterocyclic Substances. Part II. Hydroxy-Derivatives of Nitrogenous Six-Membered Ring-Compounds". Journal of the Chemical Society (Resumed). 1956: 1294–1304. doi:10.1039/JR9560001294.
^Katakura, R.; Koide, Y. (2006). "Configuration-Specific Synthesis of the Facial and Meridional Isomers of Tris(8-hydroxyquinolinate)aluminum (Alq3)". Inorganic Chemistry. 45 (15): 5730–5732. doi:10.1021/ic060594s. PMID16841973.
^Montes, V. A.; Pohl, R.; Shinar, J.; Anzenbacher, P. Jr. (2006). "Effective Manipulation of the Electronic Effects and Its Influence on the Emission of 5-Substituted Tris(8-quinolinolate) Aluminum(III) Complexes". Chemistry: A European Journal. 12 (17): 4523–4535. doi:10.1002/chem.200501403. PMID16619313.
^Bardez, E.; Devol, I.; Larrey, B.; Valeur, B. (1997). "Excited-State Processes in 8-Hydroxyquinoline: Photoinduced Tautomerization and Solvation Effects". The Journal of Physical Chemistry B. 101 (39): 7786–7793. doi:10.1021/jp971293u.
^DE 14976, Skraup, Zdenko Hanus, "Verfahren zur Darstellung der Oxychinoline durch Behandlung von Mononitro- und Monamido-Phenolen mit Glycerin und Schwefelsäure", published 1881-09-10, issued 1881-02-16
^Fleischer, H. (2005). "Structural Chemistry of Complexes of (n-1)d10ns Metal Ions with β-N-Donor Substituted Thiolate Ligands (m=0, 2)". Coordination Chemistry Reviews. 249 (7–8): 799–827. doi:10.1016/j.ccr.2004.08.024.
^Vivanco, J.M.; Bais, H.P.; Stermitz, F.R.; Thelen, G.C.; Callaway, R.M. (2004). "Biogeographical variation in community response to root allelochemistry: novel weapons and exotic invasion". Ecology Letters. 7 (4): 285–292. Bibcode:2004EcolL...7..285V. doi:10.1111/j.1461-0248.2004.00576.x.