Periodate-iodide reaction

Inorganic systems the periodate-iodide reaction. One well-studied inorganic example is the reaction between periodate and iodide ions ... 

The following alternative procedure may be used to prepare a solution of disodium hydroxylaminedisulfonate. Sodium nitrite (15 g., 0.217 mole) and 41.6 g. (0.40 mole) of sodium bisulfite are added to 250 g. of ice. With stirring, 22.5 ml. (0.40 mole) of acetic acid is added all at once and the mixture is stirred for 90 minutes in an ice hath. At the end of the stirring period the reaction solution is pH 5 and a potassium iodide-starch test is negative. A solution of 50 g. (0.47 mole) of sodium carbonate in water (total volume 250 ml.) is added. This buffered solution of disodium hydroxylaminedisulfonate may be used for electrolytic oxidation. 

A solution of dimethyloxosulfonium methylide in DMSO (30 ml) was prepared under argon from trimethyloxosulfonium iodide (9.6 mmol) and NaH (60% dispersion in oil, 9.6 mmol) at room temperature. After stirring for 90 min (the evolution of hydrogen ceased) the solution of the ylide was added dropwise to a solution of the vinyl sulfoxide (3.2 mmol) in DMSO (25 ml) over a 30 min period. The reaction mixture was stirred at room temperature for 14h, poured into an ice water mixture, and extracted twice with ether. The ether layers were washed twice with water, dried over anhydrous MgS04 and evaporated in vacuo to give a crude cyclopropyl sulfoxide as a white solid. Flash chromatography (silica, ethyl acetate/n-hexane (25 75) gave the (7 c,Ss) isomer (1.02g, 82%), m.p. 227-228°C and the (Sc,5s) isomer (0.17g, 14%), m.p. 202-203°C. 

Preliminary examinations of dextran structures were conducted by optical rotation, infrared spectroscopy and periodate-oxidation reactions. More detailed results can be achieved by methylation analysis [19]. The hydroxyl groups are methylated with methyl iodide after activation with sodium methylsulfinyl carbanion (Fig. 2). The methyl dextran is hydrolysed to the corresponding different methylated monosaccharides, which are furthermore reduced and peracetylated. The resulting alditol acetates of methylated sugars are separated by gas chromatography and identified by their retention times. In particular, a combined capillary gas-liquid chromatography/mass... 

Crystalline paraperiodic acid, H5I06, which is hygroscopic and readily soluble in water, is commercially available. Most of the salts of periodic acid are characterized by their slight solubility in water. For oxidation experiments sodium metaperiodate, NaIC>4, is the most suitable salt because of its solubility in water (9.3% at 20° and 12.6% at 25°).99 Sodium metaperiodate is commercially available and also can be obtained readily from the slightly soluble trisodium paraperiodate, Na3H2I06, by crystallization from nitric acid in the ratio of 150 cc. of water and 45 cc. of concentrated nitric add to 100 g. of salt.9 Trisodium paraperiodate is formed in 90% yield by the reaction of bromine and sodium iodide in aqueous sodium hydroxide solution at 80°.100 It is also produced in 80% yield by the oxidation of sodium iodate with chlorine in aqueous sodium hydroxide solution.99 In connection with this preparation of trisodium paraperiodate from sodium iodate, it should be noted that in the usual periodate oxidation reactions the periodate is converted quantitatively into iodate. Paraperiodic acid has been prepared in about 93% yield from trisodium paraperiodate " 1 it has been prepared also by the electrolytic oxidation 191 >192 of iodic add. 

Fig. 3. Schematic diagram of a CSTR. In the configuration shown, up to three different solutions can be pumped (by the peristaltic pump, PP) into the reactor, R. The detectors shown in the diagram are , light absorption (A/, monochromator PM, photomultiplier), platinum (redox), and iodide (or bromide) selective electrodes. The reference electrode is the Hg/Hg2S04 couple, in place of the usual calomel electrode, to avoid adventitious introduction of chloride into the reactor. In addition to these detectors, a thermocouple, or thermistor, and a pH electrode can be inserted into the reactor from above. The recordings of periodic behavior were taken from studies on the chlorite-iodide reaction...

This reaction should be done in a well-ventilated hood, t The decaborane is purified by sublimation at 60° and lO" mm. t The n-propyl isocyanide is prepared by the method of Jackson and McKusick/ using 490 g. (2.S mole) of n-propyl iodide and 454 g. (3.3 mole) of silver cyanide. It is observed that, after a long induction period, the reaction becomes quite violent. It is suggested that one half of the propyl iodide be added initially and the other half be added drop by drop over a 2-hour period. The drj- product is used without the final fractional distillation indicated in the reference. 

When aluminium and methylene iodide are allowed to stand for a considerable period, a reaction takes place and tlie mixture solidifies. The compound is white, crystalline, and highly reactive, If the reaction is allowed to take place in anhydrous ether, the aluminium dissolves, a heavy liquid is obtained, and ethylene evolved. The reaction is represented as taking place as follows —... 

An example of such a comparison is seen in the modeling of the oscillating chlorite-iodide reaction. The model initially proposed by Epstein and Kustin [39] showed only fair agreement with the experimentally observed 1 evolution, and worse agreement with the experimentally observed I2 evolution, as seen in fig. 11.5(a,b). A revised mechanism proposed by Citri and Epstein [40] predicts oscillations quite similar in shape to the experimentally observed 1 and I2 oscillations (fig. 11.5c). In many oscillatory systems the temporal variation of only a few species (essential or nonessential) can be measured. The comparison of an experimental time series with a prediction of a proposed mechanism can be made with regard to the period of the oscillations, but becomes subjective with regard to the shape of the variation. The comparisons do not easily lead to suggestions for improvements of the proposed reaction mechanism. 

Fig. 11.1 5 The experimentally determined bifnrcation structure of the chlorite-iodide reaction. The two constraints used here are the ratio of input concentrations, [CIO2 ]o/[I ]o> and the logarithm of the reciprocal residence time, log k(,. Notation filled triangles, supercritical Hopf bifurcations filled circles, saddle-node infinite period bifurcations in the region between these two kind of bifurcations, stable oscillations were observed. Open circles, excitable dynamics the smallest circles correspond to perturbations of 2 x 10 M in NaC102 the next smallest, 6 X 10 M in NaC102 the next smallest, 1.25 x 10 X x oMn - o io-2 1...

Figure 7.5 Simulation of the bromate-chlorite-iodide reaction, (a) With an error tolerance of lO", chaotic behavior is obtained, (b) Tightening the tolerance to 10" leads to the correct result, periodic behavior. (Adapted from Citri and Epstein, 1988.)...

In a closed system, the chlorite iodide reaction is a clock reaction if 1 < [I ]o/[C102 ]o < 4. Its kinetics were determined and the basic elements of a mechanism were proposed first for the batch reaction by Kern and Kim [22]. Figure 1 shows kinetic curves (iodine absorbance vs time) of the reaction with different initial ratios of the reactants. In the first part of each curve, iodine is produced at an accelerating rate. During this period, the stoichiometry is... 

The Landolt reaction (iodate + reductant) is prototypical of an autocatalytic clock reaction. During the induction period, the absence of the feedback species (Irere iodide ion, assumed to have virtually zero initial concentration and fomred from the reactant iodate only via very slow initiation steps) causes the reaction mixture to become kinetically frozen . There is reaction, but the intemiediate species evolve on concentration scales many orders of magnitude less than those of the reactant. The induction period depends on the initial concentrations of the major reactants in a maimer predicted by integrating the overall rate cubic autocatalytic rate law, given in section A3.14.1.1. 

Zirconium monochloride and zirconium monobromide [31483-18-8] are prepared in better purity by equiUbration of mixed lower haUdes with zirconium foil at 625°C (184—185) or by slowly heating zirconium tetrahaUde with zirconium turnings at 400—800°C over a period of two weeks and hoi ding at 800—850°C for a few additional days (186). Similar attempts to produce zirconium monoiodide [14728-76-8] were unsuccesshil it was, however, obtained from the reaction of hydrogen iodide with metallic zirconium above 2000 K (187). 

A mixture consisting of 0.69 g (10.5 mmoles) of zinc-copper couple, 12 ml of dry ether, and a small crystal of iodine, is stirred with a magnetic stirrer and 2.34 g (0.7 ml, 8.75 mmoles) of methylene iodide is added. The mixture is warmed with an infrared lamp to initiate the reaction which is allowed to proceed for 30 min in a water bath at 35°. A solution of 0.97 g (2.5 mmoles) of cholest-4-en-3/ -ol in 7 ml of dry ether is added over a period of 20 min, and the mixture is stirred for an additional hr at 40°. The reaction mixture is cooled with an ice bath and diluted with a saturated solution of magnesium chloride. The supernatant is decanted from the precipitate, and the precipitate is washed twice with ether. The combined ether extracts are washed with saturated sodium chloride solution and dried over anhydrous sodium sulfate. The solvent is removed under reduced pressure and the residue is chromatographed immediately on 50 g of alumina (activity III). Elution with benzene gives 0.62 g (62%) of crystalline 4/5,5/5-methylene-5 -cholestan-3/5-ol. Recrystallization from acetone gives material of mp 94-95° Hd -10°. 

Estr-5(10)-ene-3a,17 -diol (10 g, 36.2 mmoles) is added over a period of 1 hr to a refluxing mixture consisting of 60 g (0.92 moles) of zinc-copper couple, 350 ml of dry ether and 180 g (54 ml, 0.67 moles) of methylene iodide. After the addition is complete, half of the solvent is removed by distillation and 200 ml dry ether is added. The reaction mixture is then transferred to a sealed stainless steel tube and maintained for 3 hr at 92° before being cooled in an ice bath and poured into 500 ml of saturated aqueous sodium bicarbonate solution. The resultant mixture is extracted with ether and the extracts are dried over anhydrous sodium sulfate and concentrated to yield a solid residue which gives 8.4 g (80%) 5,19-cyclo-5a,10a-androstane-3a,17) -diol mp 161-163° [aJo 40° (CHCI3), on crystallization from acetone. 

The alkylation of imines by an alkyl halide to give an iminium salt will be illustrated by selected reactions over a period of years. A more complete survey is available (88). Decker and Becker (89) prepared a number of iminium salts (91, for example) by mixing methyl iodide and aromatic imines in benzene. 2,5-Dimethyl-2-pyrroline (92) has been alkylated and the... 

The filtrate was adjusted to a pH of 9 by adding concentrated ammonia, and than a 1 N aqueous iodine-potassium iodide solution was added dropwise, whereby the tetrahydro-pyrimido-[5,4-d] pyrimidine obtained by hydrogenation with zinc in formic acid was converted by oxidation into 2,6-bis-(diethanolamino)-8-piperidino-pyrimido-[5/4-d]-pyrimidine. The completion of the oxidation was checked by means of a starch solution. The major amount of the oxidation product already separated out as a deep yellow crystalline precipitate during the addition of the iodine solution. After the oxidation reaction was complete, the reaction mixture was allowed to stand for a short period of time, and than the precipitate was separated by vacuum filtration, washed with water and dried. It had a malting point of 157°C to 158°C. The yield was 8.0 g, which corresponds to 95% theory. 

A mixture of 280 g. (1.52 moles) of commercial benzidine and 880 cc. (10.23 moles) of concentrated hydrochloric acid (sp. gr. 1.182) is placed in a 5-I. round-bottomed flask and wanned on a steam bath for one to two hours, with occasional shaking, to form the dihydrochloride. The flask is then equipped with a mechanical stirrer and a dropping funnel, and cooled, with stirring, to — ro° in an ice-salt bath. When this temperature has been reached, the benzidine dihydrochloride is tetrazotized over a period of two hours with a solution of 232 g. (3.19 moles) of 95 per cent sodium nitrite in 800 cc. of water, until a faint test for nitrous acid with starch-iodide paper is obtained after twenty minutes. During this reaction, the temperature is kept below —5 °. 

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