Mercuric oxide-Bromine

BROMINATION N-Bromopolymaleimide. N-Bromosuccinimide. Mercuric oxide-Bromine. Phenyltiimethylammonium per-bromide. 2,4, 6-Tetrabromocyclohexa-2,5-dienonc. 

Methane forms explosive mixtures with air the LEL and UEL values are 5.5% and 14% by volume of air, respectively. The explosion is loudest at 10% volume concentration. The combustion of methane in air forming CO2 involves chain reactions, propagated by free radicals, CH3-, HO-, H-, and O- (Meyer 1989). Being a saturated molecule, the reactivity of methane toward most substances is very low. However, under catalytic conditions, violent reactions have been reported with halogens and certain fluorides of nonmetals. This includes reactions with chlorine at room temperature over yellow mercuric oxide, bromine pentafluoride, oxygen difluoride in the presence of a spark (MeUor 1946, Suppl. 1956), and nitrogen trifluoride (Lawless and Smith 1968). 

Alkyl hypobromites can be prepared by the reaction of alcohols with either aqueous hypobromous acid or silver oxide-bromine or mercuric oxide-bromine in an appropriate solvent. The proposed reaction sequence for hypobromite formation is shown in Scheme 9. Bromine oxide as the intermediate has been isolated and characterized. - ... 

The aHphatic iodine derivatives are usually prepared by reaction of an alcohol with hydroiodic acid or phosphoms trHodide by reaction of iodine, an alcohol, and red phosphoms addition of iodine monochloride, monobromide, or iodine to an olefin replacement reaction by heating the chlorine or bromine compound with an alkaH iodide ia a suitable solvent and the reaction of triphenyl phosphite with methyl iodide and an alcohol. The aromatic iodine derivatives are prepared by reacting iodine and the aromatic system with oxidising agents such as nitric acid, filming sulfuric acid, or mercuric oxide. 

Acids nd Sa.lts. The oxygen acids of bromine are strong oxidants but at ordinary temperatures are stable only in solution. An aqueous solution of hypobromous acid [13517-11-8] may be prepared by treating bromine water with silver oxide or mercuric oxide (69) ... 

A more concentrated solution of HOBr can be prepared by filtration of one of the above solutions and distillation in vacuum. Or the mercuric oxide reaction can be carried out in Freon 11 without water, yielding a solution of bromine monoxide which is filtered and hydrolyzed. Hypobromous acid is slightly ionized its dissociation constant at 25°C is 2 x 10 . ... 

In a modified procedure the free carboxylic acid is treated with a mixture of mercuric oxide and bromine in carbon tetrachloride the otherwise necessary purification of the silver salt is thereby avoided. This procedure has been used in the first synthesis of [1.1.1 ]propellane 10. Bicyclo[l.l.l]pentane-l,3-dicarboxylic acid 8 has been converted to the dibromide 9 by the modified Hunsdiecker reaction. Treatment of 9 with t-butyllithium then resulted in a debromination and formation of the central carbon-carbon bond thus generating the propellane 10." ... 

The rate-determining step was, therefore considered to be reaction of bromine with peroxyacetic acid to give a species (suggested as bromine acetate)which subsequently and rapidly, brominates. Formation of bromine acetate was believed to take place according to the reaction scheme represented by equilibrium (158) (which is analogous to the mercuric oxide oxidation of bromine) followed by either equilibrium (159), (160) or (161), viz. 

Twenty-four grams (0.11 mole) of red mercuric oxide (Note 1) and 60 ml. of freshly distilled 1,1,2,2-tetrachloroethane are placed in a 250-ml. three-necked flask equipped with a dropping funnel, a reflux condenser, and a stirrer. A solution of 32.2 g. (0.20 mole) of bromine and 17.2 g. (0.20 mole) of cyclopropanecarboxylic acid in SO ml. of tetrachloroethane is added dropwise to the stirred suspension of mercuric oxide over a period of 45 minutes, the flask being kept in a water bath at 30-35° (Note 2). The mixture is stirred after the addition of the reactants until the evolution of carbon dioxide ceases. 

Alkyl bromides by action of bromine and mercuric oxide on carboxylic adds, 43, 9... 

A solution of bromine in CC14 containing sulfuric acid and mercuric oxide is also a reactive brominating agent.20... 

A related method for conversion of carboxylic acids to bromides with decarboxylation is the Hunsdiecker reaction.276 The usual method for carrying out this transformation involves heating the carboxylic acid with mercuric oxide and bromine. 

Mercuric oxide, use in oxidation of hydrazones, 50, 28 with 3-chlorocyclobutanecar-boxylic acid and bromine to give l-bromo-3-chlorocyclo-butane, 51, 106 MERCURIC OXIDE-MODIFIED HUNS-DIECKER REACTION 1-BRQMO-... 

Boron trifluoride etherate, co-catalyst, 53, 30, 32 a-Bromination, selective of aralkyl ketone, 53, 111 Bromine, with 3-chlorocyclo-butanecarboxylic acid and mercuric oxide to give 1-bromo-3-chlorocyclobutane, 51, 106... 

Chlorocyclobutanecarboxylie acid, with mercuric oxide -and bromine to give 1-bromo-3-chlorocyclobutane, 51, 106... 

In a 1-1. three-necked round-bottomed flask, wrapped with aluminum foil to exclude light, and equipped with a mechanical stirrer, a reflux condenser, and an addition funnel, is suspended 37 g. (0.17 mole) of red mercuric oxide (Note 1) in 330 ml. of carbon tetrachloride (Note 2). To the flask is added 30.0 g. (0.22 mole) of 3-chlorocyclobutaneearboxylic acid (Note 3), and the mixture is heated to reflux while stirring. To the mixture is added dropwise a solution of 40 g. (0.25 mole) of bromine in 180 ml. of carbon tetrachloride as fast as possible (4-7 minutes) without loss of bromine from the condenser (Note 4). After a short induction period, carbon dioxide is evolved at a rate of 150-200 bubbles per minute (Note 5). The solution is allowed to reflux until the rate of carbon dioxide evolution slows to about 5 bubbles per minute. This will usually take 25-30 minutes (Note 6). The mixture is then cooled in an ice bath, and the precipitate is removed by filtration. The residue on the funnel is washed with carbon tetrachloride, and the filtrates are combined. The solvent is removed by distillation using a modified Claisen distillation apparatus with a 6-cm. Vigreux column, and vacuum distillation of the residual oil gives 13-17 g. (35-46%) of... 

Some variations of the method have been used to prepare cyclopropyl and cyclobutyl halides. Simultaneous addition of bromine and 3-bromocyclobutanecarboxylic acid to the suspension of mercuric oxide gives 1,3-dibromocyclobutane in good yield.7 Similarly, cyclopropanecarboxylic acid gives bromo-cyclopropane,9 and 3-(bromomethyl)cyclobutanecarboxylic acid gives 3-(bromomethyl)cyclobutyl bromide.10 In the latter reaction, it was found desirable to remove the water from the reaction as it is formed in order to obtain high yields. Another variation is the addition of a mixture of the acid and mercuric oxide to excess bromine in bromotrichloromethane.6... 

The following reactions with inorganic substances are taken from the book of Clark, Hydrazine (1953), pp 4 to 18 Potassium reacts with N2H4 expl violently (p 4) Mercuric oxide reacts with N2H4.H2O with expl violence (p 5) Chlorine, bromine and iodine react violently (p 8) with N 2H4 and spontaneous ignition of N2H) takes place in a chlorine atm. 

A. J. Balard,9 in 1821, also prepared hypobromous acid in a similar manner, namely, by the gradual addition of mercuric oxide of bromine water, and thoroughly shaking the mixture after each addition. Further, quantities of bromine and mercuric oxide can be added until the yellow fluid contains between 6 and 7 parts of HOBr per 100 c.c. The mercuric oxide can be replaced by silver oxide, silver or mercuric nitrate, mercuric acetate, etc. The soln. with 6-7 parts of HOBr per 100 c.c. decomposes at 30°, but more dil. soln. when distilled under ordinary atm. press, give a distillate of bromine followed by a straw-yellow fraction which is a dil. aq. soln. of hypobromous acid. The decomposition is not so pronounced if it be conducted at 40° under a press, of, say, 50 mm. of mercury. 

Reaction of the parent heterocycle with excess of bromine affords 2,3,4,5-tetra-bromoselenophene in quantitative yield (36BCJ157). 2-Iodoselenophene and its homologues have been obtained by iodination with iodine in the presence of mercuric oxide (56JGU3517) or by the iodine-iodic acid method (75CS(7)lll). 

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