Oxines

S-hydroxyquinoline, oxine, C9H7ON. Light brown needles, m.p. 15-16 C. Forms insoluble complexes with metals. The solubilities of the derivatives vary with pH, etc. and hence oxine is widely used in analysis. Used for estimating Mg, Al, Zn and many other metals. Many oxinates are extracted and the metal is estimated spectrophotometrically. Derivatives, e.g. 2-meIhyl tend to be specific, for, e.g.. Copper derivatives are used as fungicides. 

Hydroxyquinoline ( oxine ). The technique adopted in this preparation is based upon the fact that, in general, the reactants glycerol, amine, nitro compound and sulphuric acid can be mixed with temperature control, and then maintained at any convenient temperature below 120° without any appreciable chemical reaction taking place. A pre-mix of the amine, glycerol and sulphuric acid, maintained at a temperature which keeps it fluid (60-90°), is added in portions to a reaction vessel containiug the nitro compound and warmed with stirring to 140-170° at which temperature the Skraup reaction takes place. 

Indo-oxine, 5,8-quinolinequinone-8-hydroxy-5-quinoyl-5-imide (indicator) dissolve 0.05 g in 100 mL alcohol pH range red 6.0-8.0 blue. Cf. Berg and Becker, Z. Anal. Chem. 119 81 (1940). 

Copper quinolinolate (oxine copper) is the chelate of divalent copper and 8-hydroxyquinoline and shares most of its market with copper naphthenate, which is a complex copper salt of mixed naphthenic acids. The principal uses are in wood treatments and some military textiles, where the green color is not objectionable. Copper naphthenate has an odor but is cheaper than oxine. Both copper naphthenate and 2inc naphthenate have performed well in environment tests, with exposure to soil above-ground, as well as concrete (33). 

Solvent extraction techniques are useful in the quantitative analysis of niobium. The fluoro complexes are amenable to extraction by a wide variety of ketones. Some of the water-insoluble complexes with organic precipitants are extractable by organic solvents and colorimetry is performed on the extract. An example is the extraction of the niobium—oxine complex with chloroform (41). The extraction of the niobium—pyrocatechol violet complex with tridodecylethylammonium bromide and the extraction of niobium—pyrocatechol—sparteine complex with chloroform are examples of extractions of water-soluble complexes. Colorimetry is performed on the extract (42,43). Colorimetry may also be performed directly on the water-soluble complex, eg, using ascorbic acid and 5-nitrosahcyhc acid (44,45). 

Direct. Some radionucHdes are packaged in solution for direct sampling (qv) via a septum and injection into the patient. GalHum-67 is a marker of inflammation, infection, and various tumor types. Its half-life is 78.3 h and it is suppHed as the gallium citrate salt. Indium-111 chloride is suppHed for the labeling of white blood ceUs. The In chloride is mixed with oxine (9-hydroxyquinoline) to form a lipophilic, cationic In oxine complex, which enters the white blood ceU. The complex dissociates within the ceU, and the cationic In " ion is trapped within the ceU, owing to its charge. 

Many compounds capable of chelation have been tested for antimicrobial properties. Those showing positive results include saHcylaldoxime [94-67-7] l-nitroso-2-naphthol [131-91-9] mercaptobenzothiazol [149-30-4], dimethylglyoxime [95-45-4], saHcylaldehyde [90-02-8], cupferron [135-20-6], phenanthroline [66-71-7], isoniazid [54-85-3], thiosemicarbazones, the sulfur analogue of oxine, and numerous antibiotics (qv) including tetracyclines. Whether these compounds function exclusively, partially, or at all by virtue of their abiHty to chelate is open to debate. 

The values have been measured by a rapid reaction method, as have those for a series of 5-hydroxy and 8-hydroxy analogues of oxine (e.g. 54JCS505, 66JCS(B)436), and for other deazaflavins and pyridopyrazines (78B1942, 68JOC2393). 

Hydroxyquinoline (oxine, 8-quinolinol) [148-24-3] M 145.2, m 71-73 , 75-76 , 76 , b 267 pKj 4.91, pK 9.81. Crystd from hot EtOH, acetone, pet ether (b 60-80 ) or water. Crude oxine can be purified by pptn of copper oxinate, followed by liberation of free oxine with H2S or by steam distn after acidification with H2SO4. Stored in the dark. Forms metal complexes. [Manske et al. Can J Research 27F 359 1949 Phillips Chem Rev 56 271 1956.]... 

Oxine Blue [3-(4-hydroxyphenyl)-3-(8-hydroxy-6-quinilinyl)-l(3/f )-isobenzofuranone]... 

Moses, M., and Prioleau, P. Ct. (1985). Cutaneous histologic findings in chemical workers with and without chloracne with past exposure to 2,3,7,8-tetrachlorodibenzo-/i-d oxin. i.. 4m. Acad. Dermatol. 12, 497-506. 

It has been found that epinephrine solutions having a physiological pH and which are stable for months in storage can be prepared by combining with the epinephrine a small amount of sodium bisulfite, boric acid, and oxine (8-hydroxy-quinoline) hereinafter called 8-quinoli-nol and adjusting the pH with an alkali, such as sodium hydroxide, to the desired pH. 

Discussion. Iron(III) (50-200 fig) can be extracted from aqueous solution with a 1 per cent solution of 8-hydroxyquinoline in chloroform by double extraction when the pH of the aqueous solution is between 2 and 10. At a pH of 2-2.5 nickel, cobalt, cerium(III), and aluminium do not interfere. Iron(III) oxinate is dark-coloured in chloroform and absorbs at 470 nm. 

Procedure. Weigh out 0.0226 g of hydrated ammonium iron(III) sulphate and dissolve it in 1 L of water in a graduated flask 50 mL of this solution contain 100 g of iron. Place 50.0 mL of the solution in a 100 mL separatory funnel, add 10 mL of a 1 per cent oxine (analytical grade) solution in chloroform and shake for 1 minute. Separate the chloroform layer. Transfer a portion of the latter to a 1.0 cm absorption cell. Determine the absorbance at 470 nm in a spectrophotometer, using the solvent as a blank or reference. Repeat the extraction with a further 10 mL of 1 per cent oxine solution in chloroform, and measure the absorbance to confirm that all the iron was extracted. 

Discussion. Various metals (e.g. aluminium, iron, copper, zinc, cadmium, nickel, cobalt, manganese, and magnesium) under specified conditions of pH yield well-defined crystalline precipitates with 8-hydroxyquinoline. These precipitates have the general formula M(C9H6ON) , where n is the charge on the metal M ion [see, however, Section 11.11(c)]. Upon treatment of the oxinates with dilute hydrochloric acid, the oxine is liberated. One molecule of oxine reacts with two molecules of bromine to give 5,7-dibromo-8-hydroxyquinoline ... 

Hence 1 mole of the oxinate of a double-charged metal corresponds to 4 moles of bromine, whilst that of a triple-charged metal corresponds to 6 moles. The bromine is derived by the addition of standard 0.02Af potassium bromate and excess of potassium bromide to the acid solution. 

Full details are given for the determination of aluminium by this method. Many other metals may be determined by this same procedure, but in many cases complexometric titration offers a simpler method of determination. In cases where the oxine method offers advantages, the experimental procedure may be readily adapted from the details given for aluminium. 

Transfer 25 mL of the solution to be analysed, containing about 0.02 g of aluminium, to a conical flask, add 125 mL of water and warm to 50-60 °C. Then add a 20 per cent excess of the oxine solution (1 mL will precipitate 0.001 g of Al), when the complex Al(C9H6ON)3 will be formed. Complete the precipitation by the addition of a solution of 4.0 g of ammonium acetate in the... 

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