Hydrogen peroxide sodium thiosulfate reaction

A 250-mL, two-necked, round-bottomed flask equipped with a magnetic stirbar, thermometer, and a reflux condenser fitted with a rubber septum and balloon of argon is charged with a solution of methyltrioxorhenium (MTO) (0.013 g, 0.05 mmol, 0.1% mol equiv) in 100 mL of methanol (Note 1). Urea hydrogen peroxide (UHP) (14.3 g, 152 mmol) is added (Notes 1, 2, 3, 4), the flask is cooled in an ice bath, and dibenzylamine (9.7 mL, 50.7 mmol) is then added dropwise via syringe over 10 min (Notes 1, 5). After completion of the addition, the ice bath is removed and the mixture is stirred at room temperature (Note 6). A white precipitate forms after approximately 5 min (Note 7) and the yellow color disappears within 20 min (Note 8). Another four portions of MTO (0.1% mol equiv, 0.013 g each) are added at 30-min intervals (2.5 hr total reaction time). After each addition, the reaction mixture develops a yellow color, which then disappears only after the last addition does the mixture remain pale yellow (Note 9). The reaction flask is cooled in an ice bath and solid sodium thiosulfate pentahydrate (12.6 g, 50.7 mmol) is added in portions over 20 min in order to destroy excess hydrogen peroxide (Note 10). The cooled solution is stirred for 1 hr further, at which point a KI paper assay indicates that the excess oxidant has been completely consumed. The solution is decanted into a 500-mL flask to remove small amounts of undissolved thiosulfate. The solid is washed with 50 mL of MeOH and the methanol extract is added to the reaction solution which is then concentrated under reduced pressure by rotary evaporation. Dichloromethane (250 mL) is added to the residue and the urea is removed by filtration through cotton and celite. Concentration of the filtrate affords 10.3 g (97%) of the nitrone as a yellow solid (Note 11). 

Oxidation reactions are generally problematic because of their large heat release. For instance, the oxidation reaction of sodium thiosulfate, Na2 S2O3, by hydrogen peroxide, H2O2, for which the stoichiometric scheme is... 

The utihty stream gets started at operating temperature and flow rate. In the following experiments, the utihty stream is heated so as to initiate the reaction. The main and secondary process tines are fed with water at room temperature and with the same flow rate as one of the experiments. Once steady state is reached, operating parameters are recorded. Process tines are then fed with the reactants, hydrogen peroxide and sodium thiosulfate. At steady state, operating parameters are recorded, and a sample of a known mass of reactor products is introduced in the Dewar vessel. Temperature in the Dewar vessel is recorded until equilibrium is reached, that is, until the reaction ends. This calorimetric method is aimed at calculating the conversion rate at the product outlet and thus the conversion rate in the reactor. The latter is also determined by thermal balances between process inlet and outlet of the reactor. Finally, the reactor is rinsed with water. This procedure is repeated for each experiment... 

Keairns and Manning AIChE J., 15 (660), 1969] have used the reaction between sodium thiosulfate and hydrogen peroxide in a well-stirred flow reactor to check a computer simulation of adiabatic CSTR operation. Data on their experimental conditions and the reaction parameters are listed below. The reaction may be considered second-order in sodium thiosulfate. 

Fig. 5.1.2 Monodispersed BaS04 ellipsoids of 0.14 pm mean size, prepared by homogene-oas precipitation with the slow release of S042- ions through decomposition of thiosulfate ions by hydrogen peroxide in the presence of Ba2+ ions at 20°C. To reduce the mean size, the reaction was carried out with sodium citrate (0.1 mol dm-3). (From Ref. 1.)...

Sodium thiosulfate reacts with alkyl halides to form salts of the type RSSOjNa (Bunte salts). Alkyl disulfides may be obtained from these salts by pyrolysis or reaction with iodine or hydrogen peroxide. The yields range from 47% to 6S>%. Cyano and carboxyl groups do not interfere. Benzoylation of sodium thiosulfate produces benzoyl disulfide in 58% yield. ... 

An excellent experimental investigation that demonstrates the multiplicity of steady states was carried out by Vejtasa and Schmitz.(Figure 8-25) They studied the reaction between sodium thiosulfate and hydrogen peroxide ... 

Benzoyl disulfide has been obtained by the reaction of benzoyl chloride with hydrogen sulfide, hydrogen disulfide, hydrogen trisulfide, potassium sulfide, sodium disulfide, lead sulfide, sodium hydrosulfite, sodium thiosulfate, sulfhydrylmagnesium bromide, and thiobenzamide. It is also formed by reaction of benzoic anhydride with hydrogen sulfide. The better preparative methods involve the oxidation of thiobenzoic add by means of air,hydrogen peroxide or sulfur monochloride, or of the sodium or potassium salt by means of air, - chlorine, iodine, copper sulfate, - potassium ferricyanide, - or ferric chloride. - ... 

Complex kinetics, such as polymerization kinetics [19, 22], lead to complex types of behavior, even under isothermal operation, i.e., without the nonlinearity introduced by the rate constant s exponential dependence on temperature. Bailey [4] summarizes some cases of experimentally observed oscillations in CSTRs including chlorination of methyl chloride [7], hydrolysis of acetyl chloride [3], the reaction between methanol and hydrogen chloride [12], and the reaction between sodium thiosulfate and hydrogen peroxide [8],... 

A more quantitative feehng for what is expressed in the analysis above can be obtained by another look at the sodium thiosulfate-hydrogen peroxide reaction illustrated in Figure 6.2. Consider the relationships possible between qg and for this reaction (computed for a feed mixture of 0.8M sodium thiosulfate and 1.2M hydrogen peroxide) shown in Figure 6.8. The only variable here is f, the holding time in the reactor. Steady-state operation corresponds to the intersection of the qg and q curves, so it is apparent that three steady states are possible between t = 6.8 and 17.8 s. From the analysis of the previous section we would expect the intermediate steady state to be inherently unstable and not observable in unconstrained operation. 

Experimental verification of the above phenomena was provided by Vejtasa and Schmitz [29] for the exothermic reaction between sodium thiosulfate and hydrogen peroxide—a welltest reaction. It is useful for an adiabatic reactor to use an altered rearrangement of Eqs. 10.4.a-l, 2 whereby the rate term is eliminated to give... 

The reaction between sodium thiosulfate and hydrogen peroxide in aqueous solution... 

Problem 14.1 Hydrogen peroxide reacts with sodium thiosulfate according to the reaction,... 

In kinetic investigations of this reaction, sodium thiosulfate (substance P) of known concentration together with a little starch solution (substance Q) are added to the mixture of hydrogen peroxide and acidified iodide ions. The iodine produced by the main reaction immediately reacts with thiosulfate ions ... 

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