Dibenzoyl peroxide, determination

Diazene, furan ozonide decomposition, 730 Diazo compounds, ozone adducts, 734 Diazonium salts, TEARS assay, 667 Dibenzoyl peroxide, determination, 698 Z-Dibenzoylstilbene, tetracyclone bleaching, 734-5... 

Wheat flour, dibenzoyl peroxide determination, 698, 701 Workplace air benzoyl peroxide, 701 peracetic acid, 699 Wurster s reagent, hydroperoxide determination, 678, 684... 

A distinction between these four possibilities can be made on the basis of the kinetic isotope effect. There is no isotope effect in the arylation of deuterated or tritiated benzenoid compounds with dibenzoyl peroxide, thereby ruling out mechanisms in which a C5— bond is broken in the rate-determining step of the substitution. Paths (ii) and (iii,b) are therefore eliminated. In path (i) the first reaction, Eq. (6), is almost certain to be rate-determining, for the union of tw o radicals, Eq. (7), is a process of very low activation energy, while the abstraction in which a C—H bond is broken would require activation. More significant evidence against this path is that dimers, Arz, should result from it, yet they are never isolated. For instance, no 4,4 -dinitrobiphenyl is formed during the phenylation of... 

At pressures above 6000 bar, free radical polymerisation sometimes proceeded explosively [ 1 ]. The parameters were determined in a batch reactor for thermal runaway polymerisation of acrylonitrile initiated by azoisobutyronitrile, dibenzoyl peroxide or di-/er/-butyl peroxide [2],... 

Biesenberg, J. S. etal., J. Polym. Eng. Sci., 1976,16, 101-116 Polymerisation of methyl methacrylate initiated by oxygen or peroxides proceeds with a steady increase in velocity during a variable induction period, at the end of which a violent 90°C exotherm occurs. This was attributed to an increase in chain branching, and not to a decrease in heat transfer arising from the increasing viscosity [ 1 ]. The parameters were determined in a batch reactor for thermal runaway polymerisation of methyl methacrylate, initiated by azoisobutyronitrile, dibenzoyl peroxide or di-ferf-butyl peroxide [2],... 

Sebastian, D. H. et al., Polym. Eng. Sci., 1976, 16, 117-123 The conditions were determined for runaway/non-runaway polymerisation of styrene in an oil-heated batch reactor at 3 bar, using dibenzoyl peroxide as initiator at 3 concentrations. Results are presented diagrammatically. 

The explosive decomposition of the solid has been studied in detail [6], The effect of moisture upon ignitibility and explosive behaviour under confinement was studied. A moisture content of 3% allowed slow burning only, and at 5% ignition did not occur [7], Thermal instability was studied using a pressure vessel test, ignition delay time, TGA and DSC, and decomposition products were identified [8], The presence of acyl chlorides renders dibenzoyl peroxide impact-sensitive [9], There is a further report of a violent explosion during purification of the peroxide by Soxhlet extraction with hot chloroform [10], Residual traces of the peroxide in a polythene feed pipe exploded when it was cut with a handsaw [11]. The heat of decomposition has been determined as 1.39 kJ/g. The recently calculated value of 69° C for critical ignition temperature coincides with that previously recorded. 

A method for determination of various types of peroxides consists of RP-HPLC separation and applying post-column UV radiation to convert the peroxide to H2O2, which may be determined by CLD with bis(2,4,6-trichlorophenyl) oxalate (140) in the presence of 2,4,6,8-tetrathiomorpholinopyrimido[5,4-(J]pyrimidine (194) as fluorescence enhancer. Dibenzoyl peroxide and f-butyl perbenzoate have LOD (SNR 3) 6.8 and 7.5 p.M, respectively, and linearity range from 40 to 400 p.M. The method was applied for determination of dibenzoyl peroxide used as whitener of wheat flour, after extraction with ethanol . See a similar method in Section VLB.3. 

The parameters were determined in a batch reactor for thermal runaway polymerisation of styrene, initiated by azoisibutyronitrile, dibenzoyl peroxide or di-ferf-butyl peroxide. 

The polymericity of these compounds has been determined by osmometry (54), cryoscopy (52, 54), and mass spectrometry (52). They are hydrolyzed or oxidized by air to biaryls. Despite being oxidized to biaryls by dibenzoyl peroxide, they do not give rise to free radicals in these decompositions. 

Peroxybenzoic acid (perbenzoic acid), CgHsCOjH (mp 41-43 C), is commercially available. It is prepared from dibenzoyl peroxide according to equation 16 [293] and is obtained as a solution in chloroform. The peroxyacid content of the solution can be determined iodometrically [293]. 

A solution of dibenzoyl peroxide (10 g) in toluene (20 ml) is cooled, with stirring, to —5° and then treated during 5 min with a pre-cooled (—2°) solution of sodium (2 g) in 96% ethanol (50 ml). Sodium peroxybenzoate separates at once. To this mixture is added ice-water, in which the sodium peroxybenzoate dissolves. The aqueous peroxybenzoate solution is separated from the toluene in a separatory funnel and washed twice with ether which removes residual toluene and ethyl benzoate. This purified aqueous solution is cooled and treated with a mixture of concentrated sulfuric acid (5 g) and ice-water (60 g), and the per-oxybenzoic acid liberated is shaken into chloroform (60 ml in two portions). The chloroform extracts are united and dried over sodium sulfate they may then be used for oxidations. For preparation of crystalline peroxybenzoic acid the chloroform is evaporated in a stream of dry air at ca. 30 mm and 25-30°. The content of active oxygen is determined by iodometric titration. 

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