Acid-Induced Free-Radical Decomposition of Hydroperoxides and Peroxides: New Low-Temperature Initiator Systems for Vinyl Polymerization

Evidence for an acid-induced free-radical breakdown of tert-butyl hydroperoxide and di-tert-butyl peroxide at room temperature has been obtained from polymerization experiments with methyl methacrylate and styrene.     

Epoxides,Hydroperoxides and Peroxides in Air Pollution

A major source of air pollutants in urban areas is automobile exhaust. Olefins constitute a substantial proportion of the chemicals emitted by this source. Olefins undergo autoxidation and photochemical oxidation in air to hydroperoxides, peroxides, epoxides and other oxygenated aliphatics, frequently of low molecular weight. Long-term carcinogenicity assays of these compounds in mice and rats by various routes of administration have shown that some of these compounds are carcinogenic. Hence, their detection and elimination as air pollutants should be vigorously pursued. This report describes the current status of air pollution research on these compounds, their carcinogenicity, structure-activity relationships and areas which deserve attention in future research. Oxidation products of aromatic hydrocarbon pollutants are also important and will be described.     

Phase-Transfer Catalytic Alkylation of Hydroperoxides: A Convenient Route to Mixed Dialkyl Peroxides

The solid-liquid phase transfer catalytic alkylation of hydroperoxides using solid potassium hydroxide as a base and TEBAC as a phase transfer catalyst is reported. When the alkylating agent is a primary bromide, this reaction represents a simple and quick method for the synthesis of mixed dialkyl peroxides in fair yields.     

Acid-Induced Free-Radical Decomposition of Hydroperoxides: Quantal Calculations

Abstract

Quantum mechanical calculations using the GAUSSIAN 76 system of programs are used to suggest a possible mechanism for the acid-induced free-radical decomposition of hydroperoxides.     

Dialkyl Peroxides Decomposition in the Presence of Quaternary Ammonium Halides

Decomposition of dicumyl peroxide and cumyl tert-butyl peroxide was studied in the presence of tetraethylammonium halides in acetonitrile, dimethylformamide, 2-propanol, and acetic acid. The tetraethylammonium halides accelerate the decomposition of dialkyl peroxides in 2-propanol and acetic acid, but do not affect the reaction velocity in dimethylformamide and acetonitrile. The decomposition products character depends on the solvent nature.     

Effect of Mineral Fillers on the Molecular Mobility of Oligoester Acrylates

Molecular mobility of oligo(carbonate methacrylate) filled with aerosil, silicon dioxide, and hydroxyapatite was studied by the spin probe method. The addition of fillers was wound to decrease the molecular mobility of oligomer chains and broaden the set of the frequencies of molecular motions. The oligomer boundary layers were disclosed to be in the glassy state. An increase in the filler content caused a rise in the fraction of the glassy domains in oligomer.     

Formation and Decomposition of Nitrocyanamide in Strong Mineral Acids

Nitrourea is the major product of acid-catalyzed decomposition of nitrocyanamide. Study of the kinetics of this process in aqueous sulfuric and nitric acid unexpectedly revealed a fairly high resistance of nitrocyanamide to acids, so that it can be synthesized not only in alkaline but also in strongly acid media.     

The Preparation of Perovskite Nano Powder by Sol-gel from DTPA and the Mechanism of Thermal Decomposition

Dy0.8Sr0.2FeO3 nano powder, a synthetic oxide, is made by sol-gel method from metal nitrate and diethylenetriaminepentaaeetic acid (DTPA), and the processing parameters are optimized.The process of the preparation, thermal decomposition and the property of the powder are studied by TG-DTA, IR, TEM, and XRD. The diameter of the average grain is about 70 nm. This new technique can be used in the preparation and the studying of ha‘no materials in the complex oxide system.     

Catalytic Systems Based on Magnesium and Zinc Compounds in the Oxidation Reactions of Alkylarenes and the Decomposition Reactions of the Corresponding Hydroperoxides

The oxidation of aromatic hydrocarbons in the presence of magnesium and zinc 2-ethylhexanoates and a mixed catalyst based on these compounds is studied. It is shown that magnesium and zinc carboxylates are active catalytic systems which catalyze the decomposition of hydroperoxides representing the primary alkylarene oxidation products alongside with activation of oxygen.     

Excitation of Chemiluminescence as a Reversal of Radiationless Transition: Semiempirical Simulation of Decomposition of Peroxides

Excitation of chemiluminescence is treated as a reversal of radiationless transition. The thermolysis of six 1,2-dioxetanes was examined by the semiempirical PM3 method. The major contribution to the reaction coordinate is made first by the stretching of the O–O bond and then by the cleavage of the C–C and O–O bonds. The energy profile is characterized by a shallow well (4–12 kJ/mol) in the region of the biradicaloid transition state. Here, the potential energy surfaces of the ground state and the triplet state are close to one other, and according to the Hund rule, the state T₁ lies lower than S₀. The well prolongs the lifetime . Therefore, the yield of chemiexcitation of the triplet product k _isc may be sufficiently high even at a low value of the rate constant k _isc of the spin-forbidden transition from S₀ to T₁. Methodological problems and the specifics of a quantum-chemical computer experiment (reliability of the Dewar semiempirical methods, reproducibility, and systematic and random errors) are considered.     

十二烷基硫酸钠减慢二苯胺-4-重氮盐及重氮树脂在水溶液中热分解反应的机理

以二苯胺重氮盐(DDS)为模型化合物, 系统考察了其在水中热分解反应与十二烷基硫酸钠(SDS)的浓度以及溶液中小分子电解质的关系, 结合荧光分析结果, 证实了DDS及重氮树脂(DR)在SDS溶液中热稳定性的提高是由于DDS和DR分子与SDS分子间的疏水相互作用和静电吸引作用使它们同SDS分子共同形成混合预胶束或胶束, 通过预胶束或胶束的静电及极性效应使其中的DDS和DR分子上的重氮基得到保护. 随着SDS浓度和小分子电解质(NaCl)浓度的增加, 进入预胶束或胶束中的DDS和DR的量越多, 体系的热稳定性提高得越大. 由于DDS和DR在远低于SDS的临界胶束浓度时(≈10-5 mol/L)形成了预胶束, 从而在SDS浓度很低时即能对DDS和DR起明显的保护作用.     

十二烷基硫酸钠减慢二苯胺—4—重氮盐及重氮树脂在水溶？…

以二苯胺重氮盐（ＤＤＳ）为模型化合物,系统考察了其在水中热分解反应与十二烷基硫酸钠（ＳＷＳ）的浓度以及溶液中小分子电解质的关系。结合荧光分析结果,证实了ＤＤＳ及重氮树脂（ＤＲ）在ＳＤＳ溶液中热稳定性的提高是由于ＤＤＳ和ＤＲ分子与ＳＤＳ分子间的疏水相互作用和静电吸引作用使它们同ＳＤＳ分子共同形成混合预胶束或胶束,通过预胶束或胶束的静电及极性效应使其中的ＤＤＳ和ＤＲ分子上的重氮基得到保护。随着ＳＤＳ浓     

Effect of Mineral Fillers on the Heat Resistance and Combustibility of an Intumescent Fireproofing Formulation on Silicone Base

An intumescent fireproofing formulation on silicone base, modified with mineral components (calcium carbonate, wollastonite, aluminosilicate microspheres), was studied by synchronous thermal analysis (Netzsch SТА 449 F5 Jupiter®). Introduction of 2–20 wt % wollastonite or aluminosilicate microspheres enhances the heat resistance (the ash residue increases by 27–40%) and reduces the combustibility of the modified fireproofing formulations (the total thermal effect of thermolysis of the fireproofing formulation decreases by a factor of more than 3). The optimum content of wollastonite and aluminosilicate microspheres is 5 wt %. Addition of calcium carbonate gave no complex positive effect.     

Effect of High Pressure on the Kinetics and Mechanism of Thermolysis of Organic Peroxides in Solution

This review analyzes published data and experimental results obtained by the authors concerning the effect of high pressure on the chemical kinetics of thermal decomposition of the main types of organic and organosilicon peroxides in solution. The volume effect of activation was found to depend on the mechanism of peroxide decomposition and on the properties of solvents.     

Experimental and Computational Studies on the CH Amination Mechanism of Tetrahydrocarbazoles via Hydroperoxides

The acid‐catalyzed reactions of photochemically generated tetrahydrocarbazole peroxides with anilines have been studied experimentally and computationally to identify the underlying reaction mechanism. The kinetic data indicate a reaction order of one in the hydroperoxide and zero in the aniline. Computational investigations using density functional theory support the experimental findings and predict an initial tautomerization between an imine and enamine substructure of the primarily generated tetrahydrocarbazole peroxide to be the rate controlling step. The enamine tautomer then loses hydrogen peroxide upon protonation, generating a stabilized allylic carbocation that is reversibly trapped by solvent or aniline to form the isolated products.     

Polymerization of Vinyl Monomers on Mineral Surfaces; A Novel Method of Preparing Reinforcing Fillers

A novel method for producing modified mineral fillers is reported: The mineral surface is first made “acidic” and this acidic surface is used to initiate the cationic polymerization of vinyl or preferably divinyl monomers, the residual acidic sites being subsequently neutralized with ammonia or an organic base. During compounding, grafting occurs between the encapsulating polymer layer and the matrix polymer via previously formed peroxidic groups in this layer or via radical attachment at unsaturated centers in the polymer coating. The incorporation of these modified fillers in various grades of polyethylene results in significant improvements in processability and in tensile and impact strength relative to the properties of equivalent composites using untreated or merely hydrophobic fillers.     

高效液相色谱法测定环己铜过氧化物

以甲醇或甲醇与水作流动相,ODS为固定相,测定环己酮的多种过氧化物。平均回收率100.2％～101.6％,测定的相对标准偏差为1.02％～2.51％。     

碱式邻苯二甲酸氢镧的热分解机理

本文测定了一水合碱式邻苯二甲酸氢镧LaOH(C_8H_5O_1)_2·H_2O的热重(TG)曲线,用红外光谱、气相色谱和质谱法表征了各步热分解产物,研究了其热分解反应机理.整个热分解过程分5步进行:LaOH(C_8H_5O_1)_2·H_2O→La_2(C_8H_4O_4)_3→La_1O(CO_3)_3(C_8H_4O_4)_2→La_2O(CO_3)_2→La_2O_2CO_3→La_2O_3.热分解的气相产物有邻苯二甲酸酐和9,10-蒽醌等.     

Kinetics and Mechanism of the Natural Mineral Marmatite Oxidation Process

Results obtained by the comparative investigations of the natural mineral marmatite (Zn,Fe)S (Stari Trg, Yugoslavia) oxidation process are presented in this paper. Determination of the oxidation process mechanism was done by thermal analysis methods: DTA-TG-DTG and DSC, while Mössbauer spectroscopy, X-ray and electronic microanalysis were used for phase composition determination of the products formed during the oxidation process. Kinetics of the process was defined for two temperature intervals 862–973 and 1023–1173 K, under isothermal conditions.     

Synthesis and Structure of Organoantimony Peroxides

Organoantimony peroxides (Ar₂SbO)₄(O₂)₂ (Ar = Ph, p-Tol) were synthesized by oxidation of triarylantimony with hydrogen peroxide in the presence of nitrosophenol or 4-chlorophenol in an ether solution. X-ray diffraction analysis of peroxides obtained revealed that four antimony atoms have octahedral coordination and are connected via bridging oxygen atoms and two peroxide groups. The C–Sb, Sb–O_br, Sb–OO, and O–O distances are equal to 2.106–2.127, 1.958–1.974, 2.202–2.246, 1.471, 1.470 Å (Ar = Ph) and 2.086–2.139, 1.932–1.983, 2.215–2.289, 1.445–1.466 Å (Ar = p-Tol).