Reduction iodide, bisulfite

The catalytic cycle of HRP can be represented by the sequence of reactions shown in Eqs. (4)-(7). This applies to most, but not all, reactions catalyzed by the enzyme, irrespective of the specific isoenzyme involved. Exceptions include the oxidations of iodide (138) and bisulfite ions (139, 140), both of which can involve a single two-electron reduction step. 

More definite evidence for the transient existence of the un-cyclized l-(jS-aminoethyl)-3,4-benzoquinones has been obtained recently by Kodja and Bouchilloux,77 78 who noted that a transient yellow color (Amax ca. 385 mp) was occasionally observed during the enzymic oxidations of catecholamines (particularly in unbuffered systems at low temperatures). This phenomenon was probably due to the formation of the transient o-quinones. (The absorption maximum of o-benzoquinone, the effective chromophore of the open-chain quinones, is known to occur at ca. 390 mp.79) An absorption maximum at 390 mp is characteristic of the formation of the dopa-quinone chromophore during oxidation of small C -terminal tyrosine peptides in the presence of tyrosinase.37 48 Similar spectroscopic features were observed when the oxidations were carried out with lead dioxide in sulfuric acid solutions (pH> 1). If the initial oxidation was carried out for a short period of time, it was possible to regenerate the original catecholamines by reduction (e.g. with sodium bisulfite, potassium iodide, and zinc powder) and to show that the 385 mp peak disappeared.77,78 Kodja and Bouchilloux were also able to identify 2,4-dinitrophenylhydrazones of several of the intermediate non-cyclized quinones by paper chromatography and spectroscopy (Amax n weakly acid solution ca. 350 mp with a shoulder at ca. 410 mp).77,78... 

The Chilean niter deposits contain up to 0.3% iodine in the form of calcium iodate. After dissolution and recrystallization of the niter, the supernatant liquor contains up to 9 g/L of sodium iodate. Iodine is liberated by reduction with sulfur dioxide (in the form of sodium bisulfite), further reduction to iodide being avoided by maintaining stoichiometry ... 

In Landolt -type reactions, iodate ion is reduced to iodide through a sequence of steps involving a reductant species such as bisulfite ion ) or arsenous acid (H2ASO3). The reaction proceeds through two overall stoichiometric processes. The Dushman reaction involves the reaction of iodate and iodide ions... 

When the naturally occurring source is iodate, the process typically employs sodium bisulfite reduction to produce iodide ... 

For the fission process, natural uranium foils and solid U02(N03)2.6H20 were used as targets. The isomer was separated with carrier from irradiated uranium foils in the following manner. The uranium was dissolved in concentrated hydrochloric acid which contained a little concentrated nitric acid. Iodide carrier was added and oxidized to periodate by means of sodium hypochlorite after the solution had been made basic with sodium carbonate. Then the usual redox steps were carried out reduction of 10 to I2 with NH2OH.HCI extraction of I2 into carbon tetrachloride back-extraction Into aqueous sodium bisulfite repetition of l2"I cycles until the y spectrum showed the presence only of iodine products or their xenon decay products. 

In one Instance (246), the sample on charcoal was transferred after Irradiation to a hot solution of sodium hydroxide, lodate carrier was added, and the radioiodine oxidized to lodate by means of hypochlorite. Following reduction of lodate to Iodide with bisulfite in acidic medium, an I -I i edox cycle was carried out In an acetate buffered solution (pH 4). Iodide was finally precipitated as the silver salt. Appropriate Iodide standards were prepared and analyzed. 

There have been further reports on routes to 3-deoxy-2-ulosonic acids. A new synthesis of Kdo involves the synthesis of epoxyester 35 (X=Br or Cl) by a Darzens reaction, followed by reaction with magnesium iodide and subsequent reduction of the 3-iodocompounds with bisulfite to give 36 deprotection by sequential acid and base treatment led to the isolation of Kdo ammonium salt (38) in 63% overall yield from the a/deAydo-sugar.34 another approach (Scheme 6) a hetero-Diels-Alder reaction was employed, followed by hydroxylation and then inversion at both C-4 and C-5 conversion of 37 to Kdo ammonium salt (38) involved functionalization at C-2 by phenylsulfenylation of an enolate.33... 

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