Perbromic acid and perbromates

The quest for perbromic acid and perbromates and the various reasons adduced for their apparent non-existence make fascinating and salutary reading. The esoteric radiochemical synthesis of Br04 in 1968 using the /3-decay of radioactive Se, whilst not providing a viable route to macroscopic quantities of perbromate. 

This stimulated the search for a chemical synthesis. Electrolytic oxidation of aqueous LiBrOs produced a 1% yield of perbromate, but the first isolation of a solid perbromate salt (RbBr04) was achieved by oxidation of BrOs with aqueous XeF2  

The best synthesis is now by oxidation of alkaline solutions of Br03 using F2 gas under rather specific conditions  

The Halogens Fluorine, Chlorine, Bromine, iodine and Astatine 

No entirely satisfactory explanation of these observations has been devised, though they are paralleled by the similar reluctance of other elements following the completion of the 3d subshell to achieve their highest oxidation states — see particularly Se (p. 755) and As (p. 552) immediately preceding Br in the periodic table. The detailed kinetics of several oxidation reactions involving aqueous solutions of Br04  

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Perbromic acid and perbromates are most readily assayed by determination of their oxidizing power after reduction with hydrogen bromide, as described earlier in this article. Traces of fluoride in the acid or salts may be determined potentio-metrically, using a fluoride-sensitive electrode (Orion Research, Inc.) and an expanded-scale pH meter. Acid or alkaline solutions should be neutralized or buffered with acetic acid and sodium acetate before the determination. The electrode response should be calibrated against similar solutions of known fluoride content. 

The existence of perbromic acid and perbromates were once considered an impossibility on the basis of thermodynamic considerations. Recently, however, these have been prepared on a regnlar laboratory scale. Perbromic acid or perbromates are synthesized by oxidation of BrOs" electrolytically or by fluorination of bromate with elemental flnorine (equation 120) or other strong fluorination agents such as Xep2 (equation 121). 

Perbromic Acid and Perbromates. Perbromates have only recently been prepared and previously there have been many papers justifying theoretically their non-existence.24 This provides an excellent example of the folly of concluding the non-existence of certain compounds until all conceivable preparative methods have been exhausted. 

The best known exceptions to the general reluctance of bromine to accept a + 7 oxidation stale are perbroinic acid and the perbromate ion, which were unknown prior to 1968 (see Chapter 17). Their subsequent synthesis has made their nonexistence" somewhat less crucial as a topic of immediate concern to inorganic chemists, but bromine certainly continues the trend started by arsenic and selenium Thus the perbromate ion is a stronger oxidizing agent than either perchlorate or periodate. 

EXAMPLE 6.16. Write formulas for the following acids (a) nitric acid, (h) chloric acid, (c) hypophosphorous acid, and (d) perbromic acid. 

There is some reason to think that bromine forms bleaching compounds, which, like those of chlorine, contain peculiar acids bromons or hypobromous acids and it is also probable that there exists a perbromic acid, analogous to perchloric acid. Our knowledge of these compounds, however, is very limited. 

LD50 (rabbits) 5 mg/kg (NIOSH 1986) produces toxic phosphine on decomposition room temperature explodes when heated rapidly decomposed by water or alcohol to HI and phosphine (ignites) ignites spontaneously with nitric acid and with perchloric, perbromic, and periodic acids ignites in contact with chlorates, bromates, and iodates when dry... 

Although the 004 and 104 ions have been known for a long time, Br04 was not synthesized until 1965. The ion was synthesized by oxidizing the bromate ion with xenon difluoride, producing xenon, hydrofluoric acid, and the perbromate ion. (a) Write the balanced equation for this reaction, (b) What are the oxidation states of Br in the Br-containing species in this reaction ... 

Nomenclature. (Review Appendix II.) (a) HNO3 is the formula for nitric acid write the formulas for nitrous acid and lead nitrate, (b) HjP04 is the formula for phosphoric acid name the acids HjPOslHgPHOs) and H3PO2 (HPH3O2). (c) Name Mg(Cl04)2. (d) HBrOj is the formula for bromic acid write the formulas for perbromic and hypobromous acids. 

Perhalates. Whereas silver perchlorate [7783-93-9] AgClO, and silver periodate [15606-77-6] AglO, are well known, silver perbromate [54494-97-2] AgBrO, has more recendy been described (18). Silver perchlorate is prepared from silver oxide and perchloric acid, or by treating silver sulfate with barium perchlorate. Silver perchlorate is one of the few silver salts that is appreciably soluble in organic solvents such as glycerol, toluene, and chlorobenzene. 

Oxidation of [Fe(phen)3] + by concentrated nitric acid is autocatalytic. " T e hen)3] + reacts with bromate by rate-determining oxidation at high bromate concentration, [Fe(bipy)3] + and ligand-substituted [Fe(phen)3] + cations react with perbromate by rate-limiting dissocia-587 Reactions of [Fe(diimine)3] + with peroxodiphosphate also involve rate-limiting dissocia-... 

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