Die Reaktion des weißen Phosphors mit Tetrachlorkohlenstoff unter dem Einfluß von Y-Strahlung, Licht und Wärme

1962 ◽  
Vol 17 (11) ◽  
pp. 703-711 ◽  
Author(s):  
D. Perner ◽  
A. Henglein
Keyword(s):  
Activation Energy ◽  
Carbon Tetrachloride ◽  
Room Temperature ◽  
Main Product ◽  
Thermal Reaction ◽  
White Phosphorus ◽  
Low Molecular Weight ◽  
Red Phosphorus ◽  
Γ Radiation ◽  
A Chain

Red phosphorus, phosphorus trichloride, trichloromethylphosphorus dichloride, hexachloroethane and a polymer consisting of carbon and chlorine are formed when solutions of white phosphorus in carbon tetrachloride are exposed to γ-radiation. Red phosphorus is the main product at room temperature. However, its yield rapidly decreases at higher temperatures and the yields of the low molecular weight products strongly increases. Typical G-values:The formation of the products PCl3 and CCl3PCl2 occurs by a chain reaction between phosphorus and carbon tetrachloride. A mechanism is proposed in which free radicals from the radiolysis of carbon tetrachloride attach the dissolved white phosphorus. The propagation of the chain is caused by chlorine transfer from carbon tetrachloride to partly trichloroalkylated or chlorinated phosphorus chains or rings. The activation energy of this transfer is found to be equal to 8.2 kcal/mole. This reaction with carbon tetrachloride is favored at high temperature while the competing process of the combination of those intermediate phosphorus chains and rings to give red phosphorus prodominates at low temperature. The red phosphorus formed contains one CCl3 group per 7 atoms of phosphorus. It was possible to synthesize trichloromethylphosphorus dichloride, trichloromethylphosphorus tetrachloride and trichloromethylphosphorus dibromide by treating the red phosphorus with chlorine or bromine, respectively.The thermal reaction between phosphorus and carbon tetrachloride also leads to PCl3 and CCl3PCl2 (ratio 1:3). Small amounts of red phosphorus and C2Cl6 could be traced too. The activation energy of the thermal reaction amounts to 22.2 kcal/moles. The photo reaction (visible light) leads to the same products. However, red phosphorus still is the main product at 100°C.

Die Reaktionen des weißen Phosphors mit Dimethyldisulfid unter γ-Bestrahlung

1968 ◽  
Vol 23 (7) ◽  
pp. 911-915 ◽  
Author(s):  
M. Scheffler ◽  
H. Drawe ◽  
A. Henglein
Keyword(s):  
Room Temperature ◽  
White Phosphorus ◽  
Red Phosphorus ◽  
Radiation Chemical ◽  
Γ Radiation ◽  
Chain Processes

Trimethylthiophosphite and red phosphorus are formed when solutions of white phosphorus in dimethyldisulfide are exposed to γ-radiation. The red phosphorus has a high content of CH3S groups. It is very reactive and can be converted into trimethylthiophosphite upon further irradiation in dimethyldisulfide suspension. Both the formation of red phosphorus from white phosphorus and the formation of trimethylthiophosphite from red phosphorus are chain processes. The radiation chemical yields are of the order of several 100 molecules/100 eV at room temperature.

scholarly journals Free Radical Chemistry of White Phosphorus: γ-Irradiation of P4 in Bromoform

1968 ◽  
Vol 23 (7) ◽  
pp. 916-921 ◽  
Author(s):  
P. Airey ◽  
H. Drawe ◽  
A. Henglein
Keyword(s):  
Free Radicals ◽  
White Phosphorus ◽  
High Yield ◽  
Red Phosphorus ◽  
Γ Irradiation ◽  
Γ Radiation ◽  
Chain Reactions ◽  
Phosphorus Containing ◽  
High Yields ◽  
Free Radical Chemistry

CHBr2PBr2 and (CHBr2)2PBr are formed in high yields and in preparatively useful amounts when solutions of white phosphorus in bromoform are exposed to γ-radiation. In the first stages of irradiation, a red phosphorus containing many groups from the solvent is the only reaction product. About 1000 molecules of P4 are consumed per 100 eV of energy absorbed. In the later stages of irradiation, free radicals from the solvent attack this red phosphorus and lead to the formation of bromophosphines in high yield. Chain reactions are formulated for the formation of both the red phosphorus and the bromophosphines.

Fragmentation, Catenation, and Direct Functionalisation of White Phosphorus by a Uranium(IV)-Silyl-Phosphino-Carbene Complex

2021 ◽  
Author(s):  
Josef Boronski ◽  
John Seed ◽  
Ashley Wooles ◽  
Stephen Liddle
Keyword(s):  
Room Temperature ◽  
White Phosphorus ◽  
Temperature Reaction ◽  
Carbene Complex

Room temperature reaction of the uranium(IV)-carbene [U{C(SiMe3)(PPh2)}(BIPMTMS)(μ-Cl)Li(TMEDA)(μ-TMEDA)0.5]2 (1, BIPMTMS = C(PPh2NSiMe3)2) with white phosphorus (P4) produces the organo-P5 compound [P5{C(SiMe3)(PPh2)}2][Li(TMEDA)2] (2) and the uranium(IV)-methanediide [U{BIPMTMS}{Cl}{μ-Cl}2{Li(TMEDA)}] (3). This is an unprecedented...

On the use of Ozawa/Flynn/Wall method to determine aging activation energy for elastomers

2021 ◽  
pp. 009524432110203
Author(s):  
Sudhir Bafna
Keyword(s):  
Mechanical Properties ◽  
Activation Energy ◽  
Weight Loss ◽  
Oxygen Consumption ◽  
Dwell Time ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Degradation Mechanism ◽  
Kinetics Of ◽  
Wall Method

It is often necessary to assess the effect of aging at room temperature over years/decades for hardware containing elastomeric components such as oring seals or shock isolators. In order to determine this effect, accelerated oven aging at elevated temperatures is pursued. When doing so, it is vital that the degradation mechanism still be representative of that prevalent at room temperature. This places an upper limit on the elevated oven temperature, which in turn, increases the dwell time in the oven. As a result, the oven dwell time can run into months, if not years, something that is not realistically feasible due to resource/schedule constraints in industry. Measuring activation energy (Ea) of elastomer aging by test methods such as tensile strength or elongation, compression set, modulus, oxygen consumption, etc. is expensive and time consuming. Use of kinetics of weight loss by ThermoGravimetric Analysis (TGA) using the Ozawa/Flynn/Wall method per ASTM E1641 is an attractive option (especially due to the availability of commercial instrumentation with software to make the required measurements and calculations) and is widely used. There is no fundamental scientific reason why the kinetics of weight loss at elevated temperatures should correlate to the kinetics of loss of mechanical properties over years/decades at room temperature. Ea obtained by high temperature weight loss is almost always significantly higher than that obtained by measurements of mechanical properties or oxygen consumption over extended periods at much lower temperatures. In this paper, data on five different elastomer types (butyl, nitrile, EPDM, polychloroprene and fluorocarbon) are presented to prove that point. Thus, use of Ea determined by weight loss by TGA tends to give unrealistically high values, which in turn, will lead to incorrectly high predictions of storage life at room temperature.

scholarly journals Synthesis and electrical characterization of Ca2Nd4Ti6O20 ceramics

2016 ◽  
Vol 34 (1) ◽  
pp. 164-168
Author(s):  
Raz Muhammad ◽  
Muhammad Uzair ◽  
M. Javid Iqbal ◽  
M. Jawad Khan ◽  
Yaseen Iqbal ◽  
...  
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Room Temperature ◽  
Sol Gel ◽  
Electrical Characterization ◽  
Sintered Sample ◽  
First Time ◽  
Alkoxide Precursors ◽  
Room Temperature Dielectric Constant

AbstractCa2Nd4Ti6O20, a layered perov skite structured material was synthesized via a chemical (citrate sol-gel) route for the first time using nitrates and alkoxide precursors. Phase analysis of a sample sintered at 1625 °C revealed the formation of an orthorhombic (Pbn21) symmetry. The microstructure of the sample after sintering comprised rod-shaped grains of a size of 1.5 to 6.5µm. The room temperature dielectric constant of the sintered sample was 38 at 100 kHz. The remnant polarization (Pr) and the coercive field (Ec) were about 400 μC/cm2 and 8.4 kV/cm, respectively. Impedance spectroscopy revealed that the capacitance (13.7 pF) and activation energy (1.39 eV) of the grain boundary was greater than the capacitance (5.7 pF) and activation energy (1.13 eV) of the grain.

About the Electrical Activation of 1×1020 cm-3 Ion Implanted Al in 4H-SiC at Annealing Temperatures in the Range 1500 - 1950°C

2018 ◽  
Vol 924 ◽  
pp. 333-338 ◽  
Author(s):  
Roberta Nipoti ◽  
Alberto Carnera ◽  
Giovanni Alfieri ◽  
Lukas Kranz
Keyword(s):  
Activation Energy ◽  
Sheet Resistance ◽  
Annealing Time ◽  
Thermal Activation ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Thermal Activation Energy ◽  
Electrical Activation ◽  
Temperature Range ◽  
Annealing Temperatures

The electrical activation of 1×1020cm-3implanted Al in 4H-SiC has been studied in the temperature range 1500 - 1950 °C by the analysis of the sheet resistance of the Al implanted layers, as measured at room temperature. The minimum annealing time for reaching stationary electrical at fixed annealing temperature has been found. The samples with stationary electrical activation have been used to estimate the thermal activation energy for the electrical activation of the implanted Al.

Kinetic Model of the 1,2-Propanediol Oxidation Reaction in the Presence of 3wt%Pd/α-Al2O3 Catalyst

2021 ◽  
Vol 903 ◽  
pp. 143-148
Author(s):  
Svetlana Cornaja ◽  
Svetlana Zhizhkuna ◽  
Jevgenija Vladiko
Keyword(s):  
Activation Energy ◽  
Lactic Acid ◽  
Kinetic Model ◽  
Catalytic Oxidation ◽  
Molecular Oxygen ◽  
Oxidation Reaction ◽  
Main Product ◽  
Oxidation Process ◽  
Water Solution ◽  
Reaction Conditions

Supported 3wt%Pd/α-Al₂O₃ catalyst was tested in selective oxidation of 1,2-propanediol by molecular oxygen. It was found that the catalyst is active in an alkaline water solution. Lactic acid was obtained as the main product of the reaction. Influence of different reaction conditions on 1,2-PDO conversion and oxidation process selectivity was studied. Partial kinetic orders of the reaction with respect to 1,2-propanediol, c0(NaOH), p(O2), n(1,2-PDO)/n(Pd)) were determined and an experimental kinetic model of the catalytic oxidation reaction was obtained. Activation energy of the process was calculated and was found to be about 53 ± 5 kJ/mol.

scholarly journals Metal- and Oxidant-Free Photoinduced Aromatic Trifluoromethylation Performed in Aerated Gel Media: Determining the Effects on Yield and Selectivity

Molecules ◽  
2018 ◽  
Vol 24 (1) ◽  
pp. 29 ◽  
Author(s):  
Alex Abramov ◽  
Hendrik Vernickel ◽  
César Saldías ◽  
David Díaz Díaz
Keyword(s):  
Molecular Weight ◽  
Room Temperature ◽  
Homogeneous Solution ◽  
Product Distribution ◽  
Blocking Effect ◽  
Low Molecular Weight ◽  
Metal Free ◽  
Potential Benefits ◽  
Media Concentration ◽  
Reaction Media

In this work we have investigated the potential benefits of using supramolecular gel networks as reaction media to carry out air-sensitive metal-free light-induced trifluoromethylation of six-membered (hetero)arenes under aerobic conditions. This reaction was performed at room temperature (RT) using sodium triflinate (CF3SO2Na, Langlois’ reagent) as a source of radicals and diacetyl as electron donor. The effects of confinement in gel media, concentration of reactants, and type of light source on yield and product distribution were evaluated and compared to the results obtained in homogeneous solution. Four different low molecular weight (LMW) gelators were employed in this study. The results confirmed the blocking effect of the gel medium against reaction quenching by external oxygen, as well as a certain control on the kinetics and selectivity.

scholarly journals On the explosion of chain-thermal reactions

1982 ◽  
Vol 24 (2) ◽  
pp. 194-202 ◽  
Author(s):  
R. O. Ayeni
Keyword(s):  
Activation Energy ◽  
Asymptotic Analysis ◽  
Upper Bound ◽  
Homogeneous Model ◽  
Chain Reaction ◽  
Isothermal Reaction ◽  
Thermal Reactions ◽  
Spatially Homogeneous ◽  
Branched Chain ◽  
A Chain

AbstractA chain reaction of oxygen (reactant) and hydrogen (active intermediary) with mtrosyl chloride (sensitizer) as a catalyst may be modelled mathematically as a non-isothermal reaction. In this paper we present an asymptotic analysis of a spatially homogeneous model of a non-isothermal branched-chain reaction. Of particular interest is the so-called explosion time and we provide an upper bound for it as a function of the activation energy which can vary over all positive values. We also establish a bound on the temperature when the activation energy is finite.

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