8-Hydroxyquinoline

8-Hydroxyquinoline
Skeletal formula of 8-hydroxyquinoline
Ball-and-stick model of the 8-hydroxyquinoline molecule
8-hydroxyquinoline
Names
Preferred IUPAC name
Quinolin-8-ol
Other names
1-Azanaphthalene-8-ol, Fennosan H 30, Hydroxybenzopyridine, Oxybenzopyridine, Oxychinolin, Oxyquinoline, Phenopyridine, Quinophenol, Oxine, 8-Quinolinol
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.005.193 Edit this at Wikidata
KEGG
UNII
  • InChI=1S/C9H7NO/c11-8-5-1-3-7-4-2-6-10-9(7)8/h1-6,11H checkY
    Key: MCJGNVYPOGVAJF-UHFFFAOYSA-N checkY
  • InChI=1/C9H7NO/c11-8-5-1-3-7-4-2-6-10-9(7)8/h1-6,11H
    Key: MCJGNVYPOGVAJF-UHFFFAOYAG
  • C1=CC2=C(C(=C1)O)N=CC=C2
Properties
C9H7NO
Molar mass 145.16 g/mol
Appearance White crystalline powder
Density 1.034 g/cm3
Melting point 76 °C (169 °F; 349 K)
Boiling point 276 °C (529 °F; 549 K)
Pharmacology
G01AC30 (WHO) A01AB07 (WHO) D08AH03 (WHO) R02AA14 (WHO)
Hazards
GHS labelling:
GHS06: ToxicGHS08: Health hazardGHS05: CorrosiveGHS09: Environmental hazard
Danger
H301, H317, H318, H360D, H410
P202, P273, P280, P301+P310, P302+P352, P305+P351+P338
Safety data sheet (SDS) External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

8-Hydroxyquinoline (also known as oxine) is an organic compound derived from the heterocycle quinoline. A colorless solid, its conjugate base is a chelating agent, which is used for the quantitative determination of metal ions.

In aqueous solution 8-hydroxyquinoline has a pKa value of ca. 9.9 It reacts with metal ions, losing the proton and forming 8-hydroxyquinolinato-chelate complexes.

Tris(8-hydroxyquinolinato)aluminium

The aluminium complex, is a common component of organic light-emitting diodes (OLEDs). Substituents on the quinoline ring affect the luminescence properties.

In its photo-induced excited-state, 8-hydroxyquinoline converts to zwitterionic isomers, in which the hydrogen atom is transferred from oxygen to nitrogen.

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.

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. 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.

By 1888 azo dyes were made from the compound.

In the 1920s insoluble chelates of 8-hydroxyquinoline were discovered.

Bioactivity

The complexes as well as the heterocycle itself exhibit antiseptic, disinfectant, and pesticide properties, functioning as a transcription inhibitor. [dubious – discuss] Its solution in alcohol is used in liquid bandages. It once was of interest as an anti-cancer drug.

A thiol analogue, 8-mercaptoquinoline is also known.

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.

Applications

Here is a list of compounds that are made from 8-hydroxyquinoline: nitroxoline, VK-28, VAR10303, cloxyquin chloroxine, 5F-PB-22, PB-22, M30, iodoquinol, broxyquinoline, chiniofon, clioquinol, quinterenol, PBT2 & clamoxyquine for example.

See also