Crystal benzoquinone

Sodium hydroxide. Dissolve a few crystals of benzoquinone in 10% aqueous NaOH solution and shake gently. The solution turns rapidly brown and then almost black owing to atmospheric oxidation. 

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]. 

Coenzyme Q4 (Ubiquinone-4, 2,3-dimethoxy-5-methyl-6-[3,7,ll,15-tetrametbyl-hexadeca-2/,6/,10/,14-tetraenyl]-[l,4]benzoquinone [4370-62-l]M 454.7, m 30 , 33-45 , A (275nm) 185. A red oil purified by TLC chromatography on Si02 and eluted with Et20-hexane. Purity can be checked by HPLC (silica column using 7% Et20-hexane). It has A- ax 270 nm (e 14,800) in pet ether. [NMR and MS Naruta J Org Chem 45 4097 1980 cf Morton Biochemical Spectroscopy (Adam Hilger, London, 1975) p 491]. It has also been dissolved in MeOH/EtOH (1 1 v/v) and kept at 5 until crystals appear [Lester and Crane Biochim Biophys Acta 32 497 1958]. 

The benzoquinone adduct is a 2 1 molecular complex of 2,3-dimethylquinoxaline and quinol, and is readily prepared by crystallizing quinol from toluene in the presence of excess of 2,3-dimethyl-quinoxaline. 2,3-Dimethylquinoxaline and A -phenylmaleimide undergo Michael addition to form the quinoxalinylmethyl-A -phenylsuccinimide... 

In 10 ml of ethanol was dissolved with heating 200 mg of 2-methyl-6-(1-methoxy-2-carba-moyloxyethyl)-1,4-benzoquinone and the resulting solution was cooled. To the cooled solution was added 0.5 ml of aziridine and then the resulting mixture was allowed to stand In a refrigerator at 5°C to 8°C for 4 days. Thereafter, the crystalline substance which precipitated in situ was recovered by filtration and washed with ethanol to give 50 mg of the desired product as red crystals melting at 200°C (with decomposition). 

The following preparation is given in U.S. Patent 3,356,573. 17a-Acetoxy-3(3-hydroxy-6-methylpregn-5-en-20-one (1 g), aluminum tert-butoxide (1 g) and p-benzoquinone (6 g) were dissolved in dry benzene (100 ml) and the mixture was heated under reflux for 30 minutes. The reaction mixture was cooled and washed with potassium hydroxide solution until the benzene layer was colorless. The benzene was washed with water, dried and evaporated to dryness under reduced pressure. The residue crystallized from aqueous methanol to give 17a-acetoxy-6-methylpregna-4,6-diene-3,20-dione, needles, MP 214° to 216°C. 

Rosenau, T. Mereiter, K. Jager, C. Schmid, P Kosma, P. Sulfonium ylides derived from 2-hydroxy-benzoquinones crystal and molecular structure and their one-step conversion into Mannich bases by amine A-oxides. Tetrahedron 2004, 60(27), 5719-5723. 

To the best of the author s knowledge, the only isolated diaza analog of o-benzoquinone is bis-N-oxide 79 and its derivatives. Compound 79 was isolated as orange-colored crystals from a reaction of tetraketo derivative 78 with dinitrogen tetroxide (76TL1703 77AP264). 

Another system with a tendency to polymorphism and in which one might expect the different crystal forms to be composed of different proton tautomers is benzoquinone oxime-nitrosophenol (8c). Here all materials studied proved to... 

Hie reaction below leads to a product, 2-(2 -hydroxy-3 -acetoxyphenylamino)-5-methoxy-l,4-benzoquinone (28), that, in solution, is an equilibrium mixture of tautomers (74). The two tautomers can be crystallized separately, the open-chain form as black crystals, the ring form as yellow ones both decompose at 176°. 

A solution of 100 mg. (0.41 mmole) of 4,4 -dimethoxybibenzyl (Note 1) in 1.5 ml. of anhydrous dioxane (Note 2) was placed in a 10-ml. round-bottomed flask. To this was added 103 mg. (0.45 mmole) of 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ Note 3) dissolved in 1.5 ml. of anhydrous dioxane. The flask was fitted with a reflux condenser and heated in an oil bath at 105° for 18 hours. The solution, which was initially deep green, became pale yellow as the hydroquinone crystallized out. The mixture was cooled, and the solid was filtered off. It was washed with 1 ml. of warm benzene followed by 6 ml. of warm chloro-... 

To 5.7 g (0.0527 mol) of p-benzoquinone is added 10 g (approximately 0.072 mol) of tin amalgam and 50 ml of glacial acetic acid. The mixture is heated on a steam bath. After 3 minutes green crystals of quinhydrone precipitate but soon dissolve to give a Ught yellow solution. After 0.5 hour the solution is filtered, the solvent is removed in vacuo, and the residue is recrystallized from benzene-acetone to give 5.0g (88%) of hydroquinone, m.p. 169-190°. 

Dioximes form bis complexes (35) where the ligand normally chelates through the nitrogen atoms.251-253 Detailed studies have been made of the partially oxidized compounds obtained from reaction of bis(diphenylglyoximato)- and bis(benzoquinone dioximato)-palladium with iodine254,255 and bromine.256 These complexes contain polyhalide anions and possess the high anisotropic electrical conductivity associated with many complexes which crystallize as stacked molecular units.257... 

The quality of the product depends to a large extent upon the purity of the benzoquinone if the latter is dark, it is advisable to crystallize it from benzene before using it/ (See Org. Syn. 2, 86.)... 

SYNTHESIS A solution of 149 g sodium thiosulfate in 300 mL H20 was vigorously stirred. To this there was added, over the course of 10 min, a solution of 43.2 g benzoquinone in 200 mL acetic acid. After an additional 1 h stirring at room temperature, all volatiles were removed under vacuum. The residual syrup slowly set up as crystals which, after grinding under brine, were removed by filtration and... 

---