Thiirene formation in the reactions of sulfur atoms with alkynes

1983 ◽  
Vol 61 (10) ◽  
pp. 2268-2281 ◽  
Author(s):  
Bela Verkoczy ◽  
Alden G. Sherwood ◽  
Imre Safarik ◽  
Otto P. Strausz
Keyword(s):  
Gas Phase ◽  
New Products ◽  
Reaction Products ◽  
Gas Phase Reactions ◽  
Bimolecular Reactions ◽  
Primary Products ◽  
End Products ◽  
Secondary Reactions

The gas phase reactions of S(1D2) and S(3PJ) atoms with alkynes have been studied by photolyzing COS in the presence of CH≡CH, CF3C≡CH, and CF3C≡CCF3. In the reactions with CH≡CH, CS2, benzene, and thiophene were formed; with CF3C≡CH, eight products were found with disubstituted thiophenes and trisubstituted benzenes as the major products. In the case of CF3C≡CCF3, only perfluorotetramethylthiophene was detected at low conversion but at long photolysis several new products were observed. Many of the reaction products characterized here have not been reported before.The formation and distribution of the reaction products could be rationalized by an overall mechanism in which the formation of the highly reactive primary adducts, thiirene and thioformylmethylene, is followed by bimolecular reactions yielding the principal end products. The formation of minor products could be explained by secondary photoisomerizations, secondary photolysis, and by secondary decompositions and the secondary reactions of sulfur atoms with primary products.

A Study on Film Precursors in SiH4 Thermal CVD by use of Trench Coverage Measurements

1989 ◽  
Vol 146 ◽  
Author(s):  
Akimasa Yuuki ◽  
Takaaki Kawahara ◽  
Yasuji Matsui ◽  
Kunihide Tachibana
Keyword(s):  
Gas Phase ◽  
Phase Reaction ◽  
Reaction Products ◽  
Gas Phase Reactions ◽  
Cross Sectional ◽  
Thermal Cvd ◽  
Silane Molecule ◽  
Cross Sectional Profile ◽  
Sticking Probabilities ◽  
Sectional Profile

ABSTRACTThe precursors of Si film in SiH4 low pressure thermal CVD are studied by use of the trench coverage analysis. The cross sectional profile of the film deposited in a trench is simulated by a direct Monte-Carlo method using the composition of the precursors and their sticking probabilities as adjustable parameters. A comparison with the experimental results[1] shows that the trench coverage profiles are well reproduced by the model where two kinds of precursors deposit independently with respective sticking probabilities of almost zero and unity. The former is silane molecule, and the latter is radicals produced by gas phase reactions. The deposition rate due to radicals can be estimated from the comparison. Considering the sticking probability and the SiH4 pyrolysis reactions, it is concluded that H3SiSiH is one of ate dominant film precursors in gas phase reaction products.

Kinetics and modelling of heptane steam-cracking

2014 ◽  
Vol 68 (12) ◽  
Author(s):  
Natália Olahová ◽  
Martin Bajus ◽  
Elena Hájeková ◽  
Lukáš Šugár ◽  
Jozef Markoš
Keyword(s):  
Flow Reactor ◽  
Frequency Factor ◽  
Product Distribution ◽  
Reaction Scheme ◽  
Reaction Products ◽  
Primary Products ◽  
Molecular Reaction ◽  
Secondary Reactions ◽  
Steam Cracking ◽  
Good Agreement

AbstractThe kinetics and product distribution during the cracking of heptane in the presence of steam were investigated. The experiments were performed in a flow reactor under atmospheric pressure in a temperature range of 680–760°C with a mass ratio of steam to heptane of 3: 1. The overall decomposition of heptane is represented by a first-order reaction with activation energy of 249.1 kJ mol−1 and a frequency factor of 3.13 × 1013 s−1. The reaction products were analysed using gas chromatography, the main product being ethylene. The molecular reaction scheme, which consists of a primary reaction and 24 secondary reactions between primary products, was used for modelling the experimental product yields. The yields of ethylene and hydrogen were in good agreement; however the experimental yields of propylene were higher than the predicted yields.

FT-IR Analysis of the Photolytic Laser-Induced Chemical Vapor Deposition of Germanium Films

1986 ◽  
Vol 40 (3) ◽  
pp. 374-378 ◽  
Author(s):  
A. E. Stanley ◽  
R. A. Johnson ◽  
J. B. Turner ◽  
A. H. Roberts
Keyword(s):  
Chemical Vapor Deposition ◽  
Gas Phase ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Gas Phase Reactions ◽  
Conversion Rates ◽  
End Products ◽  
Ft Ir ◽  
Ir Analysis ◽  
Germanium Films

Germanium and doped-germanium polycrystalline films were formed with the use of photolytic CO2 laser-induced chemical vapor deposition. The compounds which yielded germanium in large quantities were germane, ethylgermane, and diethylgermane. Triethylgermane produces germanium in trace quantities. Gas-phase reactions were monitored with the use of Fourier transform infrared spectroscopy, also used for identification of end products. Scanning electron microscopy was used for analysis of the films. The products identified on irradiation of germane were germanium and hydrogen, with conversion rates of 86%. On irradiation of diethylgermane and ethylgermane, ethylene, germane, germanium, and hydrogen were produced. Germanium films doped with cadmium and aluminum were produced successfully by the irradiation of germane mixtures containing dimethylcadmium or trimethylaluminum, respectively.

The kinetics of gas phase reactions studied in a "homogeneous reactor"

1988 ◽  
Vol 66 (9) ◽  
pp. 2325-2334 ◽  
Author(s):  
John M. Roscoe
Keyword(s):  
Gas Phase ◽  
Kinetic Studies ◽  
Gas Phase Reactions ◽  
Reaction Volume ◽  
First Order ◽  
Homogeneity Assumption ◽  
Good Spatial Resolution ◽  
Secondary Reactions ◽  
Homogeneous Reactor ◽  
Kinetics Of

The use of a "well-stirred" or "homogeneous" reactor in kinetic studies of gas phase reactions has been examined to assess the sensitivity of the method to the criteria upon which its use is based. The effects of heterogeneous and homogeneous secondary reactions are considered and the validity of the assumption of homogeneity has been examined experimentally for conditions similar to those which have been used elsewhere. The atom sink presented by the excess reagent under pseudo first order conditions results in failure of the homogeneity assumption. However, it is found that homogeneity is not required for successful use of the method provided the analytical measurements have good spatial resolution and the reaction volume is well-defined. The method is illustrated by using it to study some reactions of O(3P).

Plasma Deposition of a-Si:H

1984 ◽  
Vol 38 ◽  
Author(s):  
John C. Knights
Keyword(s):  
Gas Phase ◽  
Plasma Deposition ◽  
Substrate Surface ◽  
Silicon Film ◽  
Reaction Products ◽  
Primary Reaction ◽  
Second Stage ◽  
Third Stage ◽  
Secondary Reactions ◽  
Hydrogenated Amorphous

AbstractThere are four easily identified stages in the formation of a hydrogenated amorphous silicon film from an electrical discharge in silane. The first stage is the primary reaction between electrons and silane resulting in a mixture of ions and free radicals. The second stage is the transport of these species to the substrate surface accompanied in parallel by a multiplicity of secondary reactions e.g. ion-molecule, photon-molecule, etc. The third stage is the reaction or adsorption of these species with or onto the substrate surface and the fourth stage is the process by which these species or their reaction products incorporate into the growing film or are reemitted from the surface into the gas phase.

Gas-phase heteroaromatic substitution. 11. Electron transfer mechanism in the gas-phase acylation of simple five-membered heteroarenes

1991 ◽  
Vol 69 (4) ◽  
pp. 740-748 ◽  
Author(s):  
Antonello Filippi ◽  
Giorgio Occhiucci ◽  
Cinzia Sparapani ◽  
Maurizio Speranza
Keyword(s):  
Electron Transfer ◽  
Gas Phase ◽  
Reaction Products ◽  
Ion Chemistry ◽  
Gas Phase Reactions ◽  
Β Decay ◽  
Electron Transfer Mechanism ◽  
Gas Phase Ion Chemistry ◽  
Mass Spectrometric Evidence ◽  
Gas Phase Ion

The results of a study of the gas-phase reactions of unsaturated carbocations, such as the CH3CO+ ion from γ-radiolysis of CH3F/CO mixtures, and the C6H4TCO+ ion from the β-decay of 1,4-ditritiobenzene in the presence of CO, with pyrrole, N-methylpyrrole, furan, and thiophene, are reported. In all systems investigated, acylated heteroarenes represent the predominant reaction products, accompanied by the methylated derivatives in the CH3F/CO radiolytic mixtures, and by the phenylated ones in the 1,4-ditritiobenzene/CO decay samples. All substrates investigated are found to undergo predominant α substitution by both acetyl (88.6–98.4% (pyrrole); 90.8–98.7% (N-methylpyrrole); 97.2–98.9% (furan); 94.9–98.6% (thiophene)) and benzoyl cations (92.6–96.5% (pyrrole)) under all conditions. The predominant formation of the α-acylated pyrroles from both reactants (>88%), whose relative yields appear unaffected within the temperature interval from 303 to 383 K, indicates, in agreement with ancillary FT-ICR mass spectrometric evidence, that gas-phase acylation reactions toward simple five-membered heteroarenes proceed via a two-step substitution mechanism, involving a quasi-resonant single-electron transfer (SET) step followed by recombination of the ensuing radical – radical ion pair. By virtue of this entropy-favored mechanism, gaseous electrophiles with relatively high SCF STO-3G calculated LUMO energies such as CH3CO+ and C6H4TCO+ are effectively oriented toward the "soft" Cα sites of the selected heteroarenes, at variance with Klopman's Charge and Frontier Orbital Control predictions. The behavior of gaseous acylating reactants toward simple heteroarenes is discussed and compared with that of other gaseous electrophiles, whose reactivity appears instead in qualitative agreement with Klopman's model. Key words: gas-phase ion chemistry, electrophilic heteroaromatic substitution, nuclear decay and radiolysis, acylium ions, electron transfer.

scholarly journals Gas-Phase Reactions in the ISM: Rate Coefficients, Temperature Dependences, and Reaction Products

2011 ◽  
Vol 7 (S280) ◽  
pp. 361-371 ◽  
Author(s):  
Ian W. M. Smith
Keyword(s):  
Interstellar Medium ◽  
Gas Phase ◽  
Rate Coefficients ◽  
Reaction Products ◽  
Empirical Methods ◽  
Gas Phase Reactions ◽  
Rich Variety ◽  
Temperature Dependences ◽  
The Rich ◽  
Semi Empirical

AbstractInformation about the rate coefficients and products of processes that occur in the interstellar medium are required as input to computer models that seek to reproduce the abundances of the rich variety of molecules that have been observed in different regions of the interstellar medium. In this brief review, I seek to identify the different kinds of gas-phase processes for which information is required and to consider the experimental, theoretical, and semi-empirical methods which are employed to measure or predict rate coefficients, k(T), and how they depend on temperature (T) – and also how the products of reactions can, in favourable cases, be observed.

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