Group halates

As mentioned in Section I, disproportionation occurs most rapidly at a pH corresponding to the pKa value [Eq. (12). The velocity of formation of halate increases greatly in the order C103 < Br03 < 107 this order correlates directly with the leaving-group tendencies of the respective halide ion (see Table I). 

The thermodynamic data for complexation of trivalent lanthanide and actinide cations with halate and haloacetate anions are reported. These data are analyzed for estimates of the relative amounts of inner (contact) and outer (solvent separated) sphere complexation. The halate data reflected increasing inner sphere character as the halic acid pKa increased. Use of a Born-type equation with the haloacetic acid pKa values allowed estimation of the effective charge of the carboxylate group. These values were, in turn, used to calculate the inner sphere stability constants with the M(III) ions. This analysis indicates increasing the inner sphere complexation with increasing pKa but relatively constant outer sphere complexation. 

The hypohalites (XO ), halites (X02 ), and halates (X03 ) are oxidizing agents formed by aqueous disproportionation reactions [see Group 7A(17) Family Portrait]. Potassium chlorate is the oxidizer in safety matches. You may have heated it in the lab to form small amounts of O2 ... 

Oxidation with Hypohalites in Alkaline Solutions. In alkaline solution the halogens exist as hypohalous acid and hypohalite ions. The oxidation is likely to be more drastic than for the free halogens. Thus, whereas free iodine will not act as an oxidant, hypoiodite is a powerful oxidizing agent. Hypobromite and hypochlorite particularly are likely to produce oxidation of primary and secondary alcoholic groups and cause cleavage of carbon-carbon bonds. As noted above, the processes are complicated by the tendency of hypohalite to be converted to halate ions. 

Halates are readily prepared by the base hydrolysis of the halogen. Bromates and iodates can also be synthesized by the oxidation of the halide. Only iodic acid can be isolated outside of aqueous solution. Chlorates are excellent oxidizing agents, lodate occurs naturally, is a source of elemental iodine, and is a primary standard for iodimetry. The perhalic acids of chlorine and iodine are much easier to prepare than that of bromine. Perchloric acid, like sulfuric and phosphoric acid in previous groups, has a tetrahedral structure around the central atom and involves dir-pir... 

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