Hydroperoxide, 1,1-dimethylethyl

Boron trifluoride diethyl etherate Sodium bicarbonate Palladium on charcoal Sodium periodate Hydroperoxide, 1,1-dimethylethyl Titanium tetraisopropoxide Ethyl diisopropylamine Triethylamine Ammonium sulfate Trimethylsilyl triflate d-3-oxo-a-D-gluco-pyranoside -oxo-a-D-erythro-hexopyranoside... 

Directions given [1] for the preparation of 2-phenyl-1,1-dimethylethyl hydroperoxide by adding sulfuric acid to a mixture of the alcohol and 90% hydrogen peroxide are wrong [2] and will lead to explosion [3], The acidified peroxide (30-50% solution is strong enough) is preferably added to the alcohol, with suitable cooling and precautions [2],... 

See Alcohols, above, also Oxygenated compounds, etc., below See 2-(4-Chlorophenyl)-1,1-dimethylethyl hydroperoxide... 

The equilibrium between 1,1-dimethylethylperoxyl radicals and 1,1-dimethylethyl tetroxide was first evidenced by Bartlett and Guaraldi [157] for peroxyl radicals generated by irradiation of bis( 1,1-dimethylethyl) peroxycarbonate in CH2C12 at 77 K and oxidation of 1,1-dimethylethyl hydroperoxide with lead tetraacetate at 183 K in CH2C12. A series of studies of this equilibrium were performed later using the EPR technique (see Table 2.12). It is seen that the enthalpy of tetroxide decomposition ranges from 29 to 47 kJ mol-1. 

In addition to this reaction, many other reactions of hydroperoxide decay occur in solution and they will be discussed later. This is the reason why the unimolecular decomposition of hydroperoxides was studied preferentially in the gas phase. The rate constants of the unimolecular decomposition of some hydroperoxides in the gas phase and in solution are presented in Table 4.11. The decay of 1,1-dimethylethyl hydroperoxide in solution occurs more rapidly. This demonstrates the interaction of ROOH with the solvent. 

Let us compare the rate constants of decay of one molecule (kn) and a complex of two molecules (ki2) of 1,1-dimethylethyl hydroperoxide. 

Enthalpies, Activation Energies, and Rate Constants of the Reactions of 1,1-Dimethylethyl Hydroperoxide with Monomers Me3COOH + CH2... 

The formed hydroxyperoxide decomposes into free radicals much more rapidly than alkyl hydroperoxide [128]. So, the equilibrium addition of the hydroperoxide to the ketone changes the rate of formation of the radicals. This effect was first observed for cyclohexanone and 1,1-dimethylethyl hydroperoxide [128]. In this system, the rate of radical formation increases with an increase in the ketone concentration. The mechanism of radical formation is described by the following scheme ... 

In the case of cobalt ions, the inverse reaction of Co111 reduction with hydroperoxide occurs also rather rapidly (see Table 10.3). The efficiency of redox catalysis is especially pronounced if we compare the rates of thermal homolysis of hydroperoxide with the rates of its decomposition in the presence of ions, for example, cobalt decomposes 1,1-dimethylethyl hydroperoxide in a chlorobenzene solution with the rate constant kd = 3.6 x 1012exp(—138.0/ RT) = 9.0 x 10—13 s—1 (293 K). The catalytic decay of hydroperoxide with the concentration [Co2+] = 10 4M occurs with the effective rate constant Vff=VA[Co2+] = 2.2 x 10 6 s— thus, the specific decomposition rates differ by six orders of magnitude, and this difference can be increased by increasing the catalyst concentration. The kinetic difference between the homolysis of the O—O bond and redox decomposition of ROOH is reasoned by the... 

The decay of 1,1-dimethylethyl hydroperoxide into free radicals under action of mineral acids was also established [229]. The similar kinetic equation was observed in this system and the rate of initiation was found to be propotional to the electroconductivity of the solution. The following mechanism of free radical generation was proposed [229]. 

The reaction of olefin epoxidation by peracids was discovered by Prilezhaev [235]. The first observation concerning catalytic olefin epoxidation was made in 1950 by Hawkins [236]. He discovered oxide formation from cyclohexene and 1-octane during the decomposition of cumyl hydroperoxide in the medium of these hydrocarbons in the presence of vanadium pentaoxide. From 1963 to 1965, the Halcon Co. developed and patented the process of preparation of propylene oxide and styrene from propylene and ethylbenzene in which the key stage is the catalytic epoxidation of propylene by ethylbenzene hydroperoxide [237,238]. In 1965, Indictor and Brill [239] published studies on the epoxidation of several olefins by 1,1-dimethylethyl hydroperoxide catalyzed by acetylacetonates of several metals. They observed the high yield of oxide (close to 100% with respect to hydroperoxide) for catalysis by molybdenum, vanadium, and chromium acetylacetonates. The low yield of oxide (15-28%) was observed in the case of catalysis by manganese, cobalt, iron, and copper acetylacetonates. The further studies showed that molybdenum, vanadium, and... 

It is seen that the values of kd are very close. Hence, the reaction of POOH with the C—H bond is not the main initiation reaction. If the breakdown is a monomolecular process, the rate of O—O bond homolysis in polymer must be close to that in the gas phase. 2,2-Dimethylethyl hydroperoxide breaks down in the gas phase with a rate constant of 1.6 x 1013 exp(— 158/i 7) = 5.3 x 10 x s 1 (398 K, [4]), that is, by four orders of magnitude more slowly than in polymer. Hence, the decomposition reactions in the polymers are much faster than the monomolecular homolysis of peroxide. Decomposition reactions may be of three types (see Chapter 4), such as the reaction of POOH with a double bond... 

The reactions of sulfides with ROOH give rise to products that catalyze the decomposition of hydroperoxides [31,38-47]. The decomposition is acid-catalyzed, as can be seen from the analysis of the resulting products cumyl hydroperoxide gives rise to phenol and acetone, while 1,1-dimethylethyl hydroperoxide gives rise to 1,1-dimethylethyl peroxide, where all the three are the products of acid-catalyzed decomposition [46-49]. It is generally accepted that the intermediate catalyst is sulfur dioxide, which reacts with ROOH as an acid [31,46-50]. 

FIGURE 19.2 The correlation of rate constants of various free radical reactions with molecular mobility of nitroxyl radical in the polymer matrix of different polymers with addition of plastificator I in IPP, II in preliminary oxidized IPP, III in PE, and IV in PS. Line 1 for the reaction of 2,6-bis(l,l-dimethy-lethyl)phenoxyl radical with hydroperoxide groups at T — 295 K line 2 for the reaction of 2,2,6, 6-tetramethyl-4-bcnzoyloxypiperidinc-/V-oxyl with 1-naphthol at T = 333 K line 3 for the reaction of 2,2,6,6-tetramethyl-4-benzoyloxypiperidine-iV-oxyl with 2,6-bis(l,l-dimethylethyl)phenol at T = 333 K line 4 for the same reaction at 7 — 303 K line 5 for the same reaction at T = 313 K and line 6 for the same reaction at T — 323 K [18]. 

Chlorophenyl)-l,l-dimethylethyl hydroperoxide, 3018 2-Cyclohexenyl hydroperoxide, 2435 1,1-Dichloroethyl hydroperoxide, 0794 3,5-Dimethyl-3-hexyl hydroperoxide, 3075 Ethyl hydroperoxide, 0925... 

Phenyl-1,1-dimethylethyl hydroperoxide, 3332 2-Pheny 1-2-propyl hydroperoxide, 3166 2-Tetrahydrofuryl hydroperoxide, 1624... 

Oximino-4,5,6,7-tetrahydrobenzofmazan 77-oxide, 2357 Pentaamminedinitrogenruthenium(II) salts, 4596 Pentafluoroorthoselenic acid, 4354 Pentanesulfonic acid, 2020 Perfluoro-/er/-butanol, 1380 Peroxomonophosphoric acid, 4506 2-Phenyl-l,l-dimethylethyl hydroperoxide, 3332 77-Phenylhydroxylamine, 2356... 

Dimethylethyl hydroperoxide breaks down in the gas phase with a rate constant of... 

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