Oxalic acid, reaction with bromine

Some dehydration reactions of sulfuric acid can be very vigorous. For example, the reaction with perchloric acid produces unstable CI2O7, and a violent explosion can result. Concentrated sulfuric acid produces dangerous or toxic products with a number of other substances such as toxic carbon monoxide (CO) from reaction with oxalic acid, H2C2O4 toxic bromine and sulfur dioxide (Bf2 and SO2) from reaction with sodium bromide, NaBr and toxic, unstable chlorine dioxide (CIO2) from reaction with sodium chlorate, NaClOj. 

Phenylacetaldehyde can also be prepared by treating sodium cinna-mate with bromine, and then adding oxalic acid. The sodium salt of phenylbromolactic acid results. On steam distillation this gives ofif CO, and yields phenylacetaldehyde (the reaction is probably more complicated than the equation indicates) — ... 

By means of oxidation of the initially formed 3,4-disubstituted 5-bromo-2-bromomethylpyrrole, bromine converted 3,4-disubstituted-2-methylpyr-roles and their 5-carboxylic acids into 5-bromo-5 -bromomethyl-2,2 -dipyrrolylmethanes. Similar reaction with sulfuryl chloride led to the analogous chloro species (77MI2). Whereas treatment of 2-aroyl-l,3-dimethylpyrrole-5-acetic esters with NBS brominated the vacant ring carbon, the related oxalate ester gave the 3-bromomethyl derivative (80JMC98). 

Barakat et al. observed that on treatment with NBS in aqueous solution an a-amino acid (alanine) and a dicarboxylic acid (oxalic) undergo decarboxylation with liberation of bromine. Luck showed that a-amino acids, peptides, and proteins on treatment with NBS (2 equiv.) in aqueous solution undergo quantitative decarboxylation. The reaction is complete in 30 min. with quantitative evolution of COj, as determined in a Warburg apparatus. The first stable product formed is the aldehyde. 

OXALIC ACID (144-62-7) CjHjO. HOOCCOOH Combustible solid heat-sensitive. (combustible <215 F/101°C. Fire Rating 1). Exposure to elevated temperatures, hot surfaces, or flames causes decomposition and the formation of toxic and flammable formic acid and carbon monoxide. Hygroscopic the solution in water is a medium-strong acid. Violent reaction with strong oxidizers, acid chlorides alkali metals bromine, furfuryl alcohol hydrogen peroxide (90%) phosphorus trichloride silver powders sodium, sodium chlorite sodium hypochlorite urea + heat (forms NHj gas, CO2 and CO may explode). Mixture with some silver compounds forms explosive salts of silver oxalate. Incompatible with caustics, mercury, urea. On small fires, use dry chemical powder (such as Purple-K-... 

ACIDE OXALIQUE (French) (144-62-7) Combustible solid. Violent reaction with strong oxidizers, bromine, furfuryl alcohol, hydrogen peroxide (90%), phosphorus trichloride, silver powders, sodium chlorite, sodium hypochlorite. Mixture with some silver compounds forms explosive salts of silver oxalate. Incompatible with caustics, mercury, silver, urea. Attacks polyvinyl alcohol and acetal plastics. 

On the other hand, it must be home in mind that the energy demands usually become more exacting as the mechanism becomes more primitive. In the reaction of bromine and oxalic acid, great simplicity may be achieved by the co-operation of the positive bromine ion. But the amphoteric ionization of bromine will require a not inconsiderable amount of energy. With chlorine the corresponding dissociation will require even more, and there is evidence that the hydrolysis of chlorine takes place by the mechanism... 

Ethyl ester of oxalic 4-nitrophenylhydrazidoyl bromide ( ). The amount of 344 g (1.23 mole) of XIX is added to a mixture of 1650 ml glacial acetic acid, 900 ml of acetic anhydride and 246 g (3 moles) of sodium acetate, and the mixture is cooled to 0°C. Over a period of two hours 199 g (1.23 mole) of bromine, dissolved in 300 ml of glacial acetic acid, is added dropwise with stirring, and the reaction mixture is added to 7 liters of water. The precipitated ester (382 g, 97.5 %, m.p. 201-203°C) is filtered, washed with water, and dried. 

Replacement of chloride or bromide in tra 5 -[Pt(oxalate)2X2] by iodide proceeds by reduction to [Pt"(oxalate)2] , followed by oxidative addition to give the [Pt (oxalate)2la] product. Reaction of [Pt(SCN)g] with bases similarly has as its first step formation of [Pt"(SCN)4] . The replacement of one bromide by chloride in /ra/z5 -[Pt(CN)4Br2] and /m 5-[Pt(N02)4Br2] is catalysed by [Pt(CN)4] or [Pt(N02)4] . The reactions follow a third-order rate law the mechanism is the usual inner-sphere redox mechanism of substitution. In the cyanide case there is an additional term independent of chloride concentration in the rate law, indicating a solvent-assisted path. Closely related to these systems is the oxidative addition of bromine to [Pt(CN)4] to give rm/2j-[Pt(CN)4Br2] , which has been studied in acid solution by stopped-flow techniques. Here initial fast production of tranj -[Pt(CN)4(OH2)Br] is followed by slow displacement of water by bromide, which explains the marked catalytic effect of added bromide on the overall reaction. ... 

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