Photochemical substitution reactions of some alkylcobaloximes by hydroperoxides and the crystal structure of cumyl peroxide (pyridine) cobaloxime

Alkyl(pyridine) cobaloximes irradiated with visible light in the presence of tert-butyl or cumyl hydroperoxide give rise to tert-butyl or cumyl peroxide(pyridine)cobaloxime by photochemical substitution reaction. We report the structure of the cumyl peroxide(pyridine)cobaloxime determined by X-ray diffraction     

Synthesis and Antioxidative Activity of S-Substituted 2-Mercapto-1,4-dihydroxybenzenes

S-Substituted 2-mercapto-1,4-dihydroxybenzenes were prepared, and their antioxidative activity in autooxidation of cumene and in the reactions with cumylperoxy radicals and cumyl hydroperoxide was studied.     

Self- and heteroassociates of cumyl hydroperoxide: FTIR-spectroscopy, chemometrics (factor analysis) and quantum chemical calculations

Self- and heteroassociation of cumyl hydroperoxide and acetophenone in n-decane solutions were studied by FTIR spectroscopy (3100–3700 cm⁻¹, 298–358 K). To interpret spectroscopic data, the new approach of factor analysis was offered. Equilibrium constants and thermodynamic parameters of associate formation were determined. The DFT calculations of cumyl hydroperoxide conformations, their self- and heteroassociates were carried out.     

Evidence for significant through-space and through-bond electronic coupling in the 1,4-diphenylcyclohexane-1,4-diyl radical cation gained by absorption spectroscopy and DFT calculations

Photoinduced single-electron-transfer promoted oxidation of 2,5-diphenyl-1,5-hexadiene by using N-methylquinolinium tetrafluoroborate/biphenyl co-sensitization takes place with the formation of an intense electronic absorption band at 476 nm, which is attributed to the 1,4-diphenylcyclohexane-1,4-diyl radical cation. The absorption maximum (lambda(ob)) of this transient occurs at a longer wavelength than is expected for either the cumyl radical or the cumyl cation components. Substitution at the para positions of the phenyl groups in this radical cation by CH(3)O, CH(3), F, Cl, and Br leads to an increasingly larger redshift of lambda(ob). A comparison of the rho value, which was obtained from a Hammett plot of the electronic transition energies of the radical cations versus sigma(+), with that for the cumyl cation shows that the substituent effects on the transition energies for the 1,4-diarylcyclohexane-1,4-diyl radical cations are approximately one half of the substituent effects on the transition energies of the cumyl cation. The observed substituent-induced redshifts of lambda(ob) and the reduced sensitivity of lambda(ob) to substituent changes are in accordance with the proposal that significant through-space and -bond electronic interactions exist between the cumyl radical and the cumyl cation moieties of the 1,4-diphenylcyclohexane-1,4-diyl radical cation. This proposal gains strong support from the results of density functional theory (DFT) calculations. Moreover, the results of time-dependent DFT calculations indicate that the absorption band at 476 nm for the 1,4-diphenylcyclohexane-1,4-diyl radical cation corresponds to a SOMO-3 --> SOMO transition.     

Liquid-phase oxidation of benzothiophene and dibenzothiophene by cumyl hydroperoxide in the presence of catalysts based on supported metal oxides

The liquid-phase oxidation of benzothiophene and dibenzothiophene by cumyl hydroperoxide in the presence of supported metal oxide catalysts was carried out in octane in an N₂ atmosphere at 50–80°C. The cumyl hydroperoxide, benzothiophene, and dibenzothiophene conversions and the yield of sulfones were determined for catalysts of various natures. In the presence of MoO₃/SiO₂, the most efficient and most readily regenerable catalyst, the benzothiophene conversion was ～60% and the dibenzothiophene conversion was as high as 100% upon almost complete consumption of cumyl hydroperoxide. The influence of unsaturated and aromatic compounds (oct-1-ene, toluene) on the catalytic effect was studied. The kinetics of substrate oxidation and cumyl hydroperoxide decomposition and an analysis of the cumyl hydroperoxide conversion products suggested a benzothiophene and dibenzothiophene oxidation mechanism including the formation of an intermediate complex of the hydroperoxide with the catalyst and the substrate and its transformation via heterolytic and homolytic routes.     

FT-IR study of self-association of some hydroperoxides

Self-association of cumyl, tertiary butyl and 3-phenylmethyl hydroperoxides in solutions of n-decane, carbon tetrachloride and chlorobenzene were studied by IR spectroscopy (3100–3700 cm⁻¹, 293–353 K). The experimental data were interpreted by factor analysis and band contour resolution. The di- and trimerization constants and thermodynamic parameters of self-associates were determined. Intramolecular hydrogen bond of cumyl hydroperoxide was investigated. The conformations of tertiary butyl and cumyl hydroperoxides were studied. The solvent influence on the thermodynamic parameters of hydrogen bond was found.     

Kinetic Study of the Reaction Between Atactic Polypropylene and Dicumyl Peroxide by Differential Thermal Analysis

Abstract

The reaction kinetics of atactic polypropylene (APP) in bulk with dicumyl peroxide (DCP) as a radical generator have been studied by means of thermal differential analysis. Hydrogen abstraction from APP by cumyl radicals gives (polypropylen)yl radicals which undergo transfer to DCP, chain scission, disproportionation, and crosslinking, as well as reaction with cumyl radicals. Chain scission is shown to be the faster and crosslinking the slower of these two processes, even at temperatures of 473 K and above. Activation parameters are determined, and an analysis of the different processes is made on their basis.     

Antioxidant properties of sulfides derived from 2-propylphenol and of their aminomethyl derivatives

Antioxidant properties of sulfides derived from 2-propylphenol and of their aminomethyl derivatives were studied in a model reaction of cumene oxidation. The kinetic parameters of the reactions of these compounds with cumylperoxy radicals and cumyl hydroperoxide were determined.     

Phenomenes de complexation entre un peroxyde et les monomeres vinyliques polaires etudies par resonance magnetique protonique

The self association of cumyl hydroperoxide and its complexing with polar monomers have been studied by proton magnetic resonance. These complexations are exothermic and strongly temperature dependent. It has been suggested that the complexation of cumyl hydroperoxide by polar monomers could be one of the causes of its efficiency in initiating the radical polymerization of vinyl monomers on an ethyl-zinc terminated polyethylene chain to form radical block copolymers. However, if this phenomenon has an effect on the initiation, it should not affect the propagation mechanisms, because the hydroperoxide is destroyed by ZnEt₂ during initiation. Moreover, the tacticity of radical polymethylmethacrylate, obtained at 60° with (ZnEt₂—cumyl hydroperoxide) in heptane does not differ from the conventional radical polymer.     

Kinetics of the reaction of the 2,4,6-tri-tert-butylphenoxyl radical with aromatic amines under quasiequilibrium conditions,and the dissociation energy of the N-H bond in aromatic amines

We have studied the kinetics of the reaction of the 2,4,6-tri-tert-butylphenoxyl radical with 11 aromatic amines under quasiequilibrium conditions. The equilibrium constant for each amine was determined from the kinetic results. These values, together with their temperature dependence, were used to calculate the dissociation energy of the N-H bond in the 11 aromatic amines. By using earlier results for the reaction of the aroxyl radical with cumyl hydroperoxide, catalyzed by aromatic amines, we have calculated the rate constants for the reaction of 10 aminyl radicals with cumyl hydroperoxide and of cumylperoxy radicals with 10 aromatic amines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 743–749, April, 1990.     

Mechanism of the catalytic decomposition of cumyl hydroperoxide inhibited by 2-methylpropanol-1

The kinetics of cumyl hydroperoxide (CHP) decomposition catalyzed by molybdenyl propanediolate (Cat) and decomposition products are studied in the presence of 2-methylpropanol-1 (MP). Phenol, acetone, 2-phenylpropanol-2 (PhP), and acetophenone (APh) are the main products of cumyl hydroperoxide decomposition. The concentration of 2-methylpropanol-1 affects not only the ratio between the rates of heterolytic and homolytic decomposition of cumyl hydroperoxide, but also the ratio between the products of hydroperoxide homolysis, that is, the [2-phenylpropanol-2]/[acetophenone] ratio. The dissociation constants calculated for the catalyst-2-methylpropanol-1 and catalyst-2(2-methylpropanol-l) complexes are 0.275 and 4.910 mol/1, respectively. The exchange of hydroperoxide ligands in the ROH-catalyst-ROOH systems was studied by¹H NMR spectroscopy. Exchange interactions affect the rate and direction of hydroperoxide decomposition     

Effect of sulfur-containing phenols and amines on the decomposition of hydroperoxides

The effect of polyphenol sulfides (PPS) and dithiolthione, the sulfur-containing derivative of acetone anil, on the decomposition of cumyl andn-decyl hydroperoxides (DHP) studied. The decomposition of cumyl hydroperoxide (CHP) in the presence of PPS is a complex multistep autocatalytic process during which an efficient catalyst for CHP decomposition is formed from the initial PPS. The PPS catalyst for CHP decomposition is deactivated in the reaction with peroxy radicals. Kinetic characteristics of the reaction between polyphenol sulfides and CHP are determined. Dithiolthione catalytically decomposes CHP and reacts with n-decyl hydroperoxide DHP in the stoichiometric ratio     

Catalysis of Cumyl Hydroperoxide Decomposition by Calcium Salts and Complexes: A Kinetic Experiment and Quantum Chemical Modeling

Kinetics and Catalysis - The kinetic and thermodynamic parameters of the decomposition of cumyl hydroperoxide in a chlorobenzene medium in the presence of calcium 2-ethylhexanoate and a complex of...     

Thermolysis of free-radical initiators: tert-butylazocumene and its 1,3- and 1,4-bisazo and 1,3,5-trisazo analogues.

Four tert-butylazocumenes (4-7) were prepared from the corresponding cyanobenzenes, and their nitrogen evolution kinetics and products were analyzed. In combination with TEMPO, the simplest compound, tert-butylazocumene (4), shows promise as a "one-radical" initiator of styrene polymerization. The ABNO-trapped cumyl radical 29 is a particularly stable trialkylhydroxylamine, whose thermolysis half-life is 2.1 h at 150 degrees C. Taking advantage of this stability, we trapped the cumyl radical centers from 7 to afford tris adduct 32a. While the behavior of the meta bisazoalkane 6 can be mostly predicted from that of 4, the para isomer 5 exhibits both unusual products and kinetics, attributed to the formation of quinodimethane 33 via azo-containing radical 34. In fact, flash vacuum pyrolysis of 5 allowed observation of the (1)H and (13)C NMR spectra of 33, whose persistence even at ambient temperature showed that this quinodimethane is far more stable than the parent 36. Finally, evidence is presented that 7 is an initiator of star polymerization.     

Alkylation of alkali metal salts of hydroperoxides with haloalkanes in dipolar nonhydroxyl solvents

The possibility of alkylation with chloroalkanes of cumyl hydroperoxide sodium salt hexahydrate in dopolar nonhydroxyl solvents with high donor numbers was examined. The kinetic featutes of the process in hexamethylphosphoric triamide were studied.     

Isobutene polymerization using a chelating diborane co-initiator

Lewis acidic diborane 1 (J. Am. Chem. Soc. 1999, 121, 3244-3245) is highly effective for both proton- and cationogen-initiated isobutene polymerization in hydrocarbon media at low temperature. Reactions of diborane 1 with cumyl chloride and cumyl methyl ether were studied by variable-temperature 1H and 19F NMR spectroscopy. At low temperatures stable ion pairs 2a and 2b are formed; at higher temperatures these ion-pairs form phenyl-1,3,3-trimethylindan (3) with concomitant release of HCl to form 1 in the case of 2a or degradation of the anion (2b). Reaction between Ph3C-Cl and diborane 1 resulted in the generation of an ion-pair 4 consisting of the Ph3C cation very weakly associated with the chelated, mu-Cl counteranion as revealed by X-ray crystallography.     

Pathways of Acetol Formation in the Course of Production of Phenol and Acetone by Cleavage of Cumyl Hydroperoxide

The mechanism of acetol formation in two-stage process of sulfuric acid cleavage of cumyl hydroperoxide was studied and confirmed by comparison with related reaction systems.     

Resonance effect in solvolysis of 1-methylbenzyl chlorides

Substituent effects of p-MeO and p-MeS groups deactivated by additional m-substituents in cumyl and α-phenylethyl solvolyses were studied to provide evidence for the higher resonance demand in the α-phenylethyl system.     

Catalytic Decomposition of Cumyl Hydroperoxide under the Action of Aspartic Acid Derivatives

The inhibiting activity of aspartic acid derivatives in the stage of degenerate chain branching in decomposition of cumyl hydroperoxide was studied. The kinetic and thermodynamic parameters of the reaction were established.     

Synthesis and crystal structure of triphenyltin and lead complexes with organic peroxides

Crystalline triphenyltin cumyl and tert-butyl peroxides (Ph₃SnOOCMe₂Ph and Ph₃SnOOBu^t, respectively) and triphenyllead cumyl peroxide (Ph₃PbOOCMe₂Ph) were synthesized and characterized by single crystal and powder X-ray diffraction, NMR, FTIR and Raman spectroscopies, TG and DSC analysis. The formation of triphenyltin tert-butyl peroxide in benzene in the presence of a base was proved by ¹¹⁹Sn, ¹³C and ¹H NMR spectroscopy. To the best of our knowledge, the obtained complexes are the first structurally characterized coordination compounds of tin and lead with organic peroxides.