Chloranilic acid

Chloranilic acid (2,5-dichloro-3,6-dihydroxy-l,4-benzoquinone)/57-5S-77 M 209.0, m 283-284° pK l.22, pK 3.01. A soln of 8g in IL of boiling water was filtered while hot, then extracted twice at about 50° with 200mL portions of benzene. The aq phase was cooled in ice-water. The crystals were filtered off, washed with three lOmL portions of water, and dried at 115°. It can be sublimed in vacuum. [J Phys Chem 61 765 1957.] The diacetate has m 182-185° [7 Am Chem Soc A6 1866 1924 Thamer and Voight J Phys Chem 56 225 7952]. 

Tile same methodology as mentioned for the preparation of (9) was applied for the synthesis of 8-nitro-l,6-naphthyridines. Heating diethyl N- 3-nitropyridin-4-yl)aminomethylenemalonate (12) in diphenyl ether yields ethyl 8-nitro-l,6-naphthyridin-4(lH)-one 3-carboxylate (13) (63JCS4237, 30%) and acid treatment of 4-( y, y-diethoxypropylamino)-5-nitro-2-(/3,/3 -trifluoroethoxy)-pyridine (14) gives in a similar way 8-nitro-5-(/3, /3-triflu-oroethoxy)-l,2-dihydro-l,6-naphthyridine (15, 76%). Subsequent oxidation with chloranil, acid hydrolysis, and methylation with methyl iodide gives 8-nitro-6-methyl-l,6-naphthyridin-5(6H)-one (16,63%) (81JHC941). 

A. Mercury(II) chloranilate method Discussion. The mercury(II) salt of chloranilic acid (2,5-dichloro-3,6-dihydroxy-p-benzoquinone) may be used for the determination of small amounts of chloride ion. The reaction is ... 

Mercury(II) chloranilate may be prepared by adding dropwise a 5 per cent solution of mercury(II) nitrate in 2 per cent nitric acid to a stirred solution of chloranilic acid at 50 °C until no further precipitate forms. Decant the supernatant liquid, wash the precipitate three times by decantation with ethanol and once with diethyl ether, and dry in a vacuum oven at 60 °C. The compound is available commercially. 

Khashaba et al. [34] suggested the use of sample spectrophotometric and spectrofluorimetric methods for the determination of miconazole and other antifungal drugs in different pharmaceutical formulations. The spectrophotometric method depend on the interaction between imidazole antifungal drugs as -electron donor with the pi-acceptor 2,3-dichloro-5,6-dicyano-l,4-benzoquinone, in methanol or with p-chloranilic acid in acetonitrile. The produced chromogens obey Beer s law at Amax 460 and 520 nm in the concentration range 22.5-200 and 7.9-280 pg/mL for 2,3-dichloro-5,6-dicyano-l,4-benzoquinone and p-chloranilic acid, respectively. Spectrofluorimetric method is based on the measurement of the native fluorescence of ketoconazole at 375 nm with excitation at 288 nm and/or fluorescence intensity versus concentration is linear for ketoconazole at 49.7-800 ng/mL. The methods... 

Mahrous et al. [43] determined primaquine and other antimalarials by use of chloranilic acid for the colorimetry. Primaquine was treated with 0.2 chloranilic acid solution in acetonitrile to give a purple solution with absorption maximum at 522 nm. Beer s law was obeyed from 0.04 to 0.2 mg/mL. Analysis of pharmaceutical formulation by this method is as accurate as the official method. 

Fe +aq reacts with chloranilic acid to give iron(II) chloranilate. " Fe " aq reacts with promazine, (204), to give the promazine radical cation complex of Fe. The volume profile for this combined substitution and electron transfer reaction has been established. The activation volumes for the forward and reverse reactions are —6.2cm mol and — 12.5cm mol the respective activa-... 

Lobacz et al. [52] have described partial adsorption ofTl+-cryptand (2,2,2) complex on mercury electrode. From voltocoulom-etry, cyclic voltammetry, and chrono-coulometry, it has been deduced that electroreduction of this complex proceeds via two parallel pathways from the solution and from the adsorbed states, which are energetically close. Also, Damaskin and coworkers [53] have studied adsorption of the complexes of alkali metal cations with cryptand (2,2,2) using differential capacity measurements and a stationary drop electrode. It has been found that these complexes exhibit strong adsorption properties. Novotny etal. [54] have studied interfacial activity and adsorptive accumulation of U02 " "-cupferron and UO2 - chloranilic acid complexes on mercury electrodes at various potentials in 0.1 M acetate buffer of pH 4.6 and 0.1 M NaCl04, respectively. 

Formaldoxime, NaDDC,b triethanolamine Dithizone,b TMK, TAM,b diphenylcarbazide Dithiol,b chloranilic acid, quercitin,b tiron DMG, furildioxime,b NaDDC,b oxine,b PAR... 

Chloramphenicol, ATUO Chiorani 1, AF09 Chloranilic acid, AF16 L-ChloroacetaniIide, AM53 Chloroacetic acid, AA50 Chloroacetone, AB59 2-Chloroacetophenone, AM11... 

Substituted benzylideneanilines form molecular complexes187 with 106 and with 2,5-dichloro-3,6-dihydroxy-p-benzoquinone (110) (chloranilic acid). These complexes were investigated by IR and 111 NMR. The complexes between benzylideneanilines and 106 are CT complexes (111), while complexes with 110 are formed through electron and proton transfer187, as illustrated in 112. In 111, a refers lo n -> jr interaction and b is a jr -> jr interaction, sp2 N-atoms of some heterocyclic imines (such as 2,2 -bipyridyl, 1,10-phenantroline) are also n-donors towards acceptors (tetracyanoethylene, p-benzoquinone, chloranil)188. 

A non-aqueous titration method is described for the determination of some alkaloids including reserpine and their dosage forms using 0.005M chloranilic acid solution in l,it-dioxane as the titrant. The end point is determined by measuring the change in absorbance of the sample at 535 nm. Quantitative recoveries with good reproducibility are reported for reserpine and other alkaloids (38). 

Mahrous et al. reported the use a spectrophotometric method for the determination of dipyridamole and other cardiovascular drugs using p-chloranilic acid [30]. Tablets, or aqueous solutions containing salts of dipyridamole and the other drugs, were rendered alkaline with aqueous... 

Si/BDD electrodes are able to achieve faster oxidation and better incineration efficiency than Ti/Pb02 in the treatment of naphthol (Panizza and Cerisola 2004b) (Fig. 2.12), 4-chlorophenol (Gherardini et al. 2001), and chloranilic acid (Martinez-Huitle et al. 2004b). 

Martinez-Huitle, C. A., Quiroz, M. A., Comninellis, C., Ferro, S. and De Battisti, A. (2004b) Electrochemical incineration of chloranilic acid using Ti/Ir02, Pb/Pb02 and Si/BDD electrodes. Electrochim. Acta 50, 949-956. 

Chloranilic Acid.—Hydroxyl substitution products of quino e are important as they yield salts with bases which are intensely colored and therefore valuable as dyes. The most important one of these compounds is a di-hydroxyl product of a quinone related to anthracene and known as alizarin. A mixed chlorine and hydroxyl substitution product is the di-chlor di-hydroxy quinone. It is chloranil in which two of the chlorine atoms have been replaced by hydroxyl groups, and is known as chloranilic acid. 

Numerous methods for determining fluoride are based on compounds of thorium with organic reagents, such as Alizarin S [55], Xylenol Orange [48], Arsenazo I [4], and chloranilic acid [56]. An exceptionally sensitive method is based on the ternary system Th-Chrome Azurol S-CTA (e= 1.0-10 at 635 nm) [57]. 

There exist several indirect methods for the spectrophotometric determination of silicon. After extraction of molybdosilicic acid, the Mo has been determined with phenylfluorone [45], or 2-amino-4-chlorobenzenethiol (e = 2.0-10 ) [46]. When silicic acid is added to a solution which contains hydrofluorotitanic acid and H2O2, a yellow titanium peroxide complex is formed. Chloranilic acid has also been used for determination of silicon [47],... 

Pentachlorophenol produces a wide variety of transformation products including chloranilic acid (2,5-dichloro-3,6-dihydroxy-benzo-l,4-quinone) by hydrolysis and oxidation, a dichlorocyclo-pentanedione by ring contraction, and dichloromaleic acid by cleavage of the aromatic ring (Figure 4.4) (Wong and Crosby 1981). 

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