Peroxides, estimation

Acid Solution. Acetone and hydrogen peroxide are the principal oxidation products observed in the radiolysis of 2-propanol in sulfuric acid solution. Identical results were obtained for hydrogen peroxide estimation by both the titanium sulfate and iodide ion estimations, indicating that organic hydroperoxides were not formed or that, if formed, they rapidly decompose to acetone and hydrogen peroxide. The yields obtained are summarized in Table I. In all cases, it was clearly established that product yields were independent of dose initially. 

Chloroprene Peroxide. The efficiency of conversion of oxygen to total peroxides and hydroperoxide at various extents of oxidation was determined by iodometric methods. At up to 12% oxidation the proportion of hydroperoxide was constant at 20% of the whole. Ferrous thiocyanate likewise estimated a constant proportion (40%) of the total peroxide. Direct analysis of oxidates was somewhat difficult since the chloroprene tended to continue oxidizing during manipulation. Total peroxide estimates on chloroprene-free solutions of peroxide in toluene showed that at 20% oxidation 84% of the oxygen absorbed was present as peroxide groups. This is a minimum value since a small amount of the peroxide may have decomposed while chloroprene was being removed at —20°C. 

The decomposition of a 0.45M solution of peroxide in toluene at 35°C. was also followed by total peroxide estimation. Nearly 10% of... 

It is clear (23) that three products result from reactions of acetoxy radical pairs within the solvent cage acetyl peroxide (estimated at 38% ), methyl acetate (12.4% ), and ethane (2.9% ). The implied near equality of rates for decarboxylation of the acetoxy radicals and diffusion from the cage has been given quantitative expression in work of Braun, Rajben-bach, and Eirich (2). These workers studied the variation in the amounts of ethane and methyl acetate formed from acetyl peroxide as a function of solvent viscosity, and they derived a rate constant for the decarboxylation of acetoxy radical at 60°C. of 1.6 X 109 sec."1. 

The intensity of lipid peroxidation estimated as thiobarbituric acid reactive substances, mainly MDA, was higher in infants subjected to nitrate intake (N group) comparing to the controls (2.4 + 0.35 nmol mL vs. 0.98 + 0.13 nmol mL ) (Figure 7.4). 

Misra, N., Biswal, J., Gupta, A., Sainis, J. K., and Sabharwal, S. 2012. Gamma radiation induced synthesis of gold nanoparticles in aqueous polyvinyl pyrrolidone solution and its application for hydrogen peroxide estimation. Radiat. Phys. Chem. 81(2) 195-200. 

The reaction with acidified potassium manganate(VII) is used in the quantitative estimation of hydrogen peroxide. 

Principle. An organic compound which contains chlorine is mixed with sodium peroxide and ignited in a closed metal bomb. The chlorine is thus converted to sodium chloride, and after acidification the chloride is estimated by the Volhard volumetric method. Bromine and iodine, when constituents of organic compounds similarly treated, are converted largely into sodium bromate and iodate respectively these ions are therefore subsequently reduced by hydrazine to bromide and iodide ions, and estimated as before. 

The estimated world production capacity for hydrazine solutions is 44,100 t on a N2H4 basis (Table 6). About 60% is made by the hypochlorite—ketazine process, 25% by the peroxide—ketazine route, and the remainder by the Raschig and urea processes. In addition there is anhydrous hydrazine capacity for propellant appHcations. In the United States, one plant dedicated to fuels production (Olin Corp., Raschig process), has a nominal capacity of 3200 t. This facihty also produces the two other hydrazine fuels, monomethyUiydrazine and unsymmetrical dimethyUiydrazine. Other hydrazine fuels capacity includes AH in the PRC, Japan, and Russia MMH in France and Japan and UDMH in France, Russia, and the PRC. 

Table 18. Estimated 1993 Consumption of Organic Peroxides by Principal Types, t...

Worldwide siUcate production is estimated to be approximately 4 x 10 t/yr. The 1995 prices for typical products are given in Table 4. The price for a hquid product, normalised to a 100% soHds basis, is usually close to the price of the corresponding bulk glass. International trade of sibcates, especially bquid products, is limited by the cost of transportation rather than production costs. Production of sibcates has increased in the 1990s (Table 5). This growth is primarily attributed to an increase in the use of sibcate to make derivatives and also to use in peroxide bleaching. 

The Reich test is used to estimate sulfur dioxide content of a gas by measuring the volume of gas required to decolorize a standard iodine solution (274). Equipment has been developed commercially for continuous monitoring of stack gas by measuring the near-ultraviolet absorption bands of sulfur dioxide (275—277). The deterrnination of sulfur dioxide in food is conducted by distilling the sulfur dioxide from the acidulated sample into a solution of hydrogen peroxide, foUowed by acidimetric titration of the sulfuric acid thus produced (278). Analytical methods for sulfur dioxide have been reviewed (279). 

Mono- and dichlorotoluenes ate used chiefly as chemical iatermediates ia the manufacture of pesticides, dyestuffs, pharmaceuticals, and peroxides, and as solvents. Total annual production was limited prior to 1960 but has expanded greatly siace that time. Chlorinated toluenes ate produced ia the United States, Germany, Japan, and Italy. Siace the number of manufacturers is small and much of the production is utilised captively, statistics covering production quantities ate not available. Worldwide annual production of o- and -chlorotoluene is estimated at several tens of thousands of metric tons. Yearly productions of polychlorotoluene ate ia the range of 100—1000 tons. 

Peroxide Formation. Except for the methyl alkyl ethers, most ethers tend to absorb and react with oxygen from the air to form unstable peroxides that may detonate with extreme violence when concentrated by evaporation or distillation, when combined with other compounds that give a detonable mixture, or when disturbed by heat, shock, or friction. Appreciable quantities of crystalline soHds have been observed as gross evidence for the formation of peroxides, and peroxides may form a viscous Hquid in the bottom of ether-fiHed containers. If viscous Hquids or crystalline soHds are observed in ethers, no further tests for the detection of peroxides are recommended. Several chemical and physical methods for detecting and estimating peroxide concentrations have been described. Most of the quaHtative tests for peroxides are readily performed and strongly recommended when any doubt is present (20). 

Cumene hydroperoxide [95], benzoyl peroxide, or tert-h iiy peroxide [96]. can be used as accelerators with alkylboron initiators. The chain transfer constant for MMA to tributylborane has been estimated to be 0.647, which is comparable to tripropylamine [97]. 

The most characteristic property of the oxaziranes is tlieir strong oxidizing character which is approximately equal to that of hydrogen peroxide. Oxaziranes react with hydrochloric acid the chlorine thus liberated is, however, used up in secondary reactions. " Two equivalents of iodine are formed from acid iodide solutions according to Eq. Titration of the free iodine allows a simple estimation of... 

The quantitative phenylation of pyridine has been studied by two groups of workers. Dannley and Gregg showed that 2-, 3-, and 4-phenylpyridine are formed in relative amounts 58 28 14 in the phenylation of pyridine with dibenzoyl peroxide, as estimated by infrared spectrophotometry. Hey and his co-workers obtained the ratios shown in Table I for the phenylation of pyridine using four different sources of phenyl radicals. ... 

For benzoyl and acetyl peroxides, loss of carbon dioxide occurs in a stepwise process. Estimates of the rate constants for step c in Scheme 1 are 7 x 10 sec (benzene, 60°). The corresponding process for acetyl peroxide has k = 2x 10 sec (n-hexane, 60°), so that the lifetime of radical pairs containing acetoxy radicals is comparable to the time necessary for nuclear polarization to take place (Kaptein, 1971b Kaptein and den Hollander, 1972 Kaptein et al., 1972). Propionoxy radicals are claimed to decarboxylate 15-20 times faster than acetoxy radicals (Dombchik, 1969). 

Di-f-butyl peroxide is a commonly used free-radical initiator that decomposes according to first-order kinetics. Use the following data to estimate AVact for the decomposition in toluene at 120°C ... 

The thermal stability of peroxides can be expressed in terms of their half-hfe (ti/a)- Half-life values can be estimated in solution utilizing the technique of differential thermal analysis. These values, or more precisely the temperatures at which their half-life is equivalent, provide an indication of practical vulcanization temperatures [49] (Table 14.29). 

Po and Sutin " have disputed both the extent of the catalytic effect of chloride ion reported by Wells and Salam" and the formation constant of 5.54 (25 °C, [Cl ] = 0.300 M, n = 1.00) for FeCl estimated thereby. Wells " has replied that the value of k2 of Po and Sutin at zero chloride concentration is artifically increased because of the presence of stabiliser in their peroxide, consequently masking the catalysis. 

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