Hydrogen peroxide melting point

Rea.ctlons, When free (R-R, R -tartaric acid (4) is heated above its melting point, amorphous anhydrides are formed which, on boiling with water, regenerate the acid. Further heating causes simultaneous formation of pymvic acid, CH COCOOH pyrotartaric acid, HOOCCH2CH(CH2)COOH and, finally, a black, charred residue. In the presence of a ferrous salt and hydrogen peroxide, dihydroxymaleic acid [526-84-1] (7) is formed. Nitrating the acid yields a dinitro ester which, on hydrolysis, is converted to dihydroxytartaric acid [617 8-1] (8), which upon further oxidation yields tartronic acid [80-69-3] (9). 

Table 4. Melting Points of Some Peroxy Compounds from Aldehydes and Hydrogen Peroxide ...

Preparation of Benzoyl Peroxide.1—Hydrogen peroxide (50 c.c. of about 10 per cent aqueous solution) kept well cooled in ice and continually shaken (preferably in a glass-stoppered bottle) is treated alternately with 4 A-sodium hydroxide solution and benzoyl chloride, added each a few drops at a time the solution is maintained faintly alkaline throughout. After about 30 c.c. of alkali and 15 g. of benzoyl chloride have been used up, the hydrogen peroxide has been decomposed and the benzoyl peroxide has separated in crystalline flocks, while the odour of the chloride has almost completely disappeared. The peroxide is filtered with suction, washed with water, and dried. Yield 10-12 g. Crystallised from a little alcohol, with which it should be boiled for a short time only, the substance forms beautiful colourless prisms. Melting point 106°-108° decomp. Heat a small quantity rapidly in a dry test tube over a naked flame. An especially pure product is obtained when a 1 von Pechmann and Vanino, Ber., 1894, 27, 1510. 

Behind a shield, to a mixture of400 ml of glacial acetic acid and 80 ml (0.70 mole) of 30% aqueous hydrogen peroxide is added 16.2 gm (0.10 mole) of 2,6-dichloroaniline. The mixture is maintained at room temperature for 48 hr. The straw-yellow product which forms is removed by filtration and recrystallized from hot glacial acetic acid to yield 16.1 gm (91.3%) of an almost white product, m.p. 173°-175°C (to a pale-green melt). On recrystallization in turn from ethanol, twice from benzene, and following this by vacuum sublimation, the melting point may be raised to 175.5°-176°C. 

TABLE 4. MELTING POINTS OF SOME PEROXY COMPOUNDS FROM ALDEHYDES AND HYDROGEN PEROXIDE... 

This 2-carbamoyl-5-methylpyrazine (7.0 g) in glacial acetic acid (30 ml) and 35% (w/v) hydrogen peroxide (20 ml) was heated with stirring at 70°C for 7 h. The reaction mixture was cooled, the product which separated was filtered and washed with water to give 2-carbamoyl-5-methylpyrazine-4-oxide (5.5 g), melting point 206°-208°C. 

To a solution of 5-methoxy-2-[(3,5-dimethyl-4-methoxy-2-pyridinyl)methylthio]-lH-benzimidazole (32.9 g, 0.1 mole) in dichloromethane (200 ml) was added phthalic anhydride (20 g, 0.135 mole) and cooled in an ice salt bath. This was followed by addition of sodium carbonate (18 g, 0.17 mole) and water (20 ml). Hydrogen peroxide (12 ml, 45%, 0.16 mm mole) was added dropwise at -5°-0°C and the reaction mixture was stirred at the same temperature. When the reaction was complete as indicated by TLC, water (200 ml) was added, cooling bath was removed and the reaction mixture was stirred for 10 mins. The organic layer was separated and washed with 5% sodium carbonate solution. The separated dichloromethane solution was charcoalised and filtered through celite. The filtrate was concentrated to 100 ml and ethyl acetate 100 ml was added thereto. The separated solid was filtered, washed with ethyl acetate and dried in vacuum oven to yield 28.20 g of omeprazole. Yield 82.4% of theoretical. Melting point was 158°-160°C (dec.). 

Dihydrobenzo[c]thiophene may be oxidized to its sulfone (Table VII) with peracetic acid,28,69,87,88 aqueous hydrogen peroxide,9 or potassium permanganate,21 and when benzocyclobutene and 1,2-diphenylbenzocyclobutene are heated with sulfur dioxide, they give l,3-dihydrobenzo[c]thiophene 2,2-dioxide89 and its cis-1,3-diphenyl derivative (83),69,90 respectively [Eq. (5)]. 1,3-Dihydro-benzo[c]thiophene 2,2-dioxide also arises when the thiadiazepine (17b) is heated just above its melting point (175°-180°).34a When sulfur dioxide is passed into a solution of diphenyldiazo-... 

A study of the freezing-point curve of solutions of hydrogen peroxide in water indicates the existence of a definite hydrate H202.2H20, melting at —51° C.1... 

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