Iodate, and Periodate

Periodate and lodate.— The oxidation of vanadium(iv) by iodate(vii) proceeds via an inner-sphere mechanism with rate law 

Stopped-flow traces reveal the rapid formation of an intermediate and its slow decomposition, indicative of a process involving a species of the type [VO(OH) 1 ]. There is no specification as to the form of periodate in the complex. The corresponding oxidation of iron(u) shows a marked dependence on hydrogen-ion concentration. 25 jg suggested that both one- and two-electron transfer steps operate in the mechanism (L = I04, HL=HJ08 )  

Again there is spectrophotometric evidence for a transient complex and at high [H+] the kinetics strictly obey the second-order dependence on Fe.  

A somewhat simpler rate law is observedjji oxidation of [Cofedta)] -, In this system there is kinetic evidence for an inner-sphere process involving the complex [(edta)Co i—which undergoes an intramolecular redox transfer with the formation of a cobalt(ra)-edta complex which ring-closes to the sexadentate [Co(edta)] ion. 

The oxidation of phosphine by I n is catalysed by tungsten(vi). The reaction is also affected by the presence of halide ions (X ), which are considered as active in the redox process. At pH the reaction scheme may be expressed as 

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We examined the reaction of triose reductone with both periodate and iodate (55,56), and found that, whereas iodine was invariably set free from both sodium periodate and sodium iodate if the concentration of the reductone were greater than 10 3M, no iodine was liberated at lower concentrations (e.g. 6 x 10 4M) of substrate, even in the presence of relatively large amounts of the oxidants. 

Obviously, simultaneous reduction of both periodate and iodate occurs. 

Periodate and iodate ions may both be removed by reaction with iodide ion in acid solution this yields free iodine which can be removed by extraction209 or by centrifugation210-—or the iodine can be converted to iodide ion by titration with sodium thiosulfate.211 Periodate and iodate ions are also readily removed from solution by use of an anion-exchange resin.211a... 

Calculations derived from the measurement of final periodate consumption indicate the number of reactive groups and can often be interpreted to reveal the extent of overoxidation. Chemically, this determination involves the use of one of two general reactions. These are (a) the reduction of periodate and iodate to free iodine in acid solution, and (b) the reduction of periodate to iodate in neutral solution. 

The most common reagent used for reducing periodate and iodate to iodine... 

The analyses of periodate and iodate mixtures is readily accomplished colorimetrically at 222.5-230 m u (in the ultraviolet region).263-273 The method utilizes very low concentrations of reactants, but is useless when the reactants or products have structures which absorb light in this region of the ultraviolet absorption spectrum. Also, certain undesirable side-reactions are catalyzed by ultraviolet light.273... 

Polymer-bound periodate and iodate have been used for the oxidation of quinols to quinones in high yield (>90%) [31]. 

Infrared absorption frequenies of seleted rare earth periodates and iodates (Lokio, 1973 Lokio and... 

The potentiometric micro detection of all aminophenol isomers can be done by titration in two-phase chloroform-water medium (100), or by reaction with iodates or periodates, and the back-titration of excess unreacted compound using a silver amalgam and SCE electrode combination (101). Microamounts of 2-aminophenol can be detected by potentiometric titration with cupric ions using a copper-ion-selective electrode the 3- and... 

Compounds of the type KBr3 are usually supposed to contain a tervalent halogen the chlorates, bromates, and iodates, and compounds of the type Csl5, to contain quinquevalent halogens and the perchlorates and periodates and compounds of the type Csl7, to contain septivalent halogens. 

C. F. Rammelsberg failed to prepare a cobalt periodate, but always obtained a mixture of oxide and iodate. 

The induction period of the reaction may be curtailed 2 by (1) the presence of an excess of iodic acid, (2) an increase in the concentrations of the reactants, (3) the addition of a trace of arsenic acid, (4) the addition of a mineral acid and (5) exposure to sunlight. On the other hand, the period may be prolonged by the addition of mercuric chloride or by violent shaking. The proportion of the iodine liberated increases with the arsenious acid concentration and passes through a maximum. The iodine appears on the surface of the solution even though the latter may be covered with benzene (or occasionally it appears at a nucleus on the glass). The reduction of periodate to iodate by means of arsenite is a bimolecular reaction and is of the first order with respect to both components.3 At 25° C. it proceeds according to the velocity equation... 

The effects of such oxidants as a mixture of potassium iodate and dichromate in concentrated sulfuric and phosphoric acids (van Slyke reagent), hot solutions of chromic acid, and acidic solutions of ceric sulfate, permanganate, periodate, and hyperoxidized transition metals on a number of sugar derivatives has been described (Ref. 1, pp. 1151-1153). 

Mechanism of staining Periodic acid opens the sugar rings at cis-diol bonds (i.e., the C-2—C-3 bond of glucose) to form two aldehyde groups and iodate (IOJ). Then the =+NH2 group of the dye reacts to form a so-called Schiff base bond with the aldehyde, thus linking the dye to the carbohydrate. The basic reaction is ... 

Rubidium periodate, RbI04.—When a mixture of rubidium iodate and hydroxide in hot concentrated solution is oxidized with chlorine, the periodate is formed in colourless quadratic crystals isomorphous with those of potassium periodate, and with the density 3-918 at 16° C. At 13° C. its solubility is 0-65 gram in 100 grams of water.18... 

Small quantities of fluorides often have a beneficial effect in electrolytic oxidation, e.g., of iodate to periodate and of sulfate to persulfate the part played by the fluoride is not clear, although in most instances its presence is accompanied by an increase of anode potential. Perchlorates have sometimes been added to solutions to improve the oxidation efficiency they have an effect similar to fluorides. 

Studies of the reaction of periodate and iodide (to form iodate and iodine) show that the initial step may be (19), or... 

Reaction of periodate and hydrogen peroxide to form iodate and oxygen has been reported , but the kinetic studies are far from complete. Reproducible initial rates of reaction were observed only in the presence of low concentrations e.g. 10 M) of iodate, but even then the kinetic orders were not simple. 

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