Hydroxyquinolines properties

In the cases of 4-hydroxyquinoline and 4-methoxyquinoline the predominance of 6-nitration supports the evidence presented above that nitration in sulphuric acid proceeds via the cations. For both these compounds reaction via the neutral molecules would be expected to occur to a considerable extent at C(j) as a result of the directing properties of the hydroxyl and methoxyl groups. 

The extraction of metal ions depends on the chelating ability of 8-hydroxyquinoline. Modification of the stmcture can improve its properties, eg, higher solubility in organic solvents (91). The extraction of nickel, cobalt, copper, and zinc from acid sulfates has been accompHshed using 8-hydroxyquinohne in an immiscible solvent (92). In the presence of oximes, halo-substituted 8-hydroxyquinolines have been used to recover copper and zinc from aqueous solutions (93). Dilute solutions of heavy metals such as mercury, ca dmium, copper, lead, and zinc can be purified using quinoline-8-carboxyhc acid adsorbed on various substrates (94). 

Hydroxyquinolines (Quinolinols). A number of methods have been employed for their preparation. A modified Chichibabia reaction of quinoline ia fused KOH—NaOH at 240°C produces 70% of 2-hydroxyquiQoline [59-31-4] (121). Alternative names based on the facile keto—enol tautomerism of two of these compounds are 2(1H) and 4(lJd)-quiQolinone none of the other quinolinols show this property. The treatment of... 

Examples of preservatives are phenylmercuric nitrate or acetate (0.002% w/v), chlorhexidine acetate (0.01 % w/v), thiomersal (0.01 % w/v) and benzalkorrium chloride (0.01 % w/v). Chlorocresol is too toxic to the comeal epithehum, but 8-hydroxyquinoline and thiomersal may be used in specific instances. The principal considerahon in relation to antimicrobial properties is the activity of the bactericide against Pseudomonas aeruginosa, a major source of serious nosocomial eye infections. Although benzal-konium chloride is probably the most active of the recommended preservatives, it cannot always be used because of its incompatibility with many compounds commonly used to treat eye diseases, nor should it be used to preserve eye-drops containing anaesthetics. Since benzalkonium chloride reacts with natural mbber, silicone or butyl rabber teats should be substituted. Since silicone mbber is permeable to water vapour, products should not be stored for more than 3 months after manufacture. As with all mbber components, the mbber teat should be pre-equilibrated with the preservative prior to... 

Some useful general rules which seem to account for the fluorescent properties of metal coordination complexes of 8-hydroxyquinoline have been proposed 191,192 These are ... 

B.J. Chen, X.W. Sun, and Y.K. Li, Influences of central metal ions on the electroluminescence and transport properties of tris-8-hydroxyquinoline metal chelates, Appl. Phys. Lett., 82 3017-JO 19 (2003). 

Soroka K, Vithanage RS, Phillips DA et al (1987) Fluorescence properties of metal complexes of 8-hydroxyquinoline-5-sulfonic acid and chromatographic applications. Anal Chem 59 629-636... 

There are many interesting derivatives of quinoline and acridine obtained by substitution. In particular, 8-hydroxyquinoline (oxine) is the second complexing agent in importance after EDTA. Sulfonation in position 5 leads to a compound which is soluble in water and that exhibits outstanding fluorogenic properties (i.e. fluorescence enhancement) on complexation with metal ions (e.g. aluminum). 

Diaza-18-crown-6 substituted with 5-chloro-8-hydroxyquinoline exhibits very interesting complexing properties. For instance, M-6 is very selective for Ba2+ over other alkaline earth cations and for K+ over Na+ in methanol. Unfortunately, investigation of fluorogenic effects with other cations has not been reported. On the other hand, the fluorescence intensity of M-7 was shown to increase by a factor of 1000 in the presence of Mg2+ (in a mixture of methanol/water 1 1 v/v) whereas other alkaline earth ions have no effect. 

The nonideality of electrolyte solntions, cansed nltimately by the electrical fields of the ions present, extends also to any nonelectrolyte that may be present in the aqueous solution. The nonelecttolyte may be a co-solvent that may be added to affect the properties of the solntion (e.g., lower the relative permittivity, e, or increase the solubility of other nonelecttolytes). For example, ethanol may be added to the aqueous solution to increase the solnbility of 8-hydroxyqni-noline in it. The nonelectrolyte considered may also be a reagent that does not dissociate into ions, or one where the dissociation is snppressed by the presence of hydrogen ions at a sufficient concentration (low pH cf Chapter 3), snch as the chelating agent 8-hydroxyquinoline. 

Ashbrook, A. W. Commercial chelating solvent extraction reagents, II. w-Al-kenyl-8-hydroxyquinoline Purification and properties, Metallurgy Division, Mines Branch, Dept. Energy, Mines and Resources, Canada Report EMA 73-34 1973. 

Diazoxine, a red product which accompanies the formation of 8-methoxy-quinoline from 8-hydroxyquinoline and diazomethane, was first encountered by Caronna and Sansone in 1939. Later, it was suggested that the properties of this product were consistent with structure 189 (R = Me, R = R = H). ° Subsequently, this product has been prepared by treatment of the iodide 190 with potassium carbonate, and the betaine structure has been confirmed by spectroscopic and chemical studies. Compound 189 (R = Me, R = R = H) is isolated as hydrated violet-red needles. The UV and visible spectra are strongly dependent on the nature of the solvent the colors of solutions vary from yellow to blue. Bromination gives the 5,7-dibromo derivative (189 R = Me, R = R = Br), which is also obtained from... 

Phenanthroline has been included in a patent as an inhibitor of the polymerization of unsaturated nitriles, such as acrylonitrile.545 Because of its fluorescent properties, it has been patented for use in a luminescent electrolytic cell.546 547 It has also been investigated as a coolant in nuclear reactors.548,549 6-Hydroxy-1,7-phenanthroline, as a derivative of 8-hydroxyquinoline, can be used for the spectrophotometric determination of iron (III)550 and vanadium(V).551... 

Metal chelates of 8-hydroxyquinoline such as (111) with photoconductive properties are reported to be useful in electrophotographic systems.233 The incorporation of a tin complex into a photo-conductive zinc oxide layer is stated to reduce dark decay . In other words, the electrostatic charge applied to the photoconductor has a longer lifetime. Two of the complexes disclosed for this application are (112) and (113). These compounds are prepared from dibutyltin oxide by reaction with 2-mercaptopropionic add and thioglycolic acid, respectively 234... 

Although they do not appear to have found application, lanthanide metal complexes of 8-hydroxyquinoline, 2-picolinic acid and catechol have been found to exhibit fungicidal properties.155... 

Iodoquinol (diiodohydroxyquin) is a halogenated hydroxyquinoline. It is an effective luminal amebicide that is commonly used with metronidazole to treat amebic infections. Its pharmacokinetic properties are poorly understood. Ninety percent of the drug is retained in the intestine and excreted in the feces. The remainder enters the circulation, has a half-life of 11-14 hours, and is excreted in the urine as glucuronides. 

Acetonitrile and benzonitrile, aliphatic amines, pyridine, amides (especially DMF), alcohols, and propylene-carbonate are used as solvents in the syntheses of this type. All of them have properties of ligands. Moreover, such classic N-donors as 2,2 -bipy and 1,10-phen were used as ligands, as well as compounds with P-(triphenylphosphine) and O- donor centers (urea, pyridine-N-oxide, triphenyl-phosphinoxide) and chelating ligand systems ((3-diketones, 8-hydroxyquinoline, dimethylglioxime) [202]. 

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