Transposition des cations radicaux aminés en spectrométrie de masse

1984 ◽  
Vol 62 (5) ◽  
pp. 931-938 ◽  
Author(s):  
Henri Edouard Audier ◽  
Jean Pierre Denhez ◽  
Arielle Milliet ◽  
Georges Sozzi
Keyword(s):  
Mass Spectrometry ◽  
Nitrogen Atom ◽  
Gas Phase ◽  
Internal Energy ◽  
Experimental Results ◽  
Ammonia Molecule ◽  
Hydrogen Shift ◽  
Spectrométrie De Masse ◽  
Good Agreement

It is demonstrated in mass spectrometry that alkylamines substituted at C2 and containing weak internal energy isomerize in the gas phase into intermediary ions composed of ionized cyclopropanes complexed with an ammonia molecule. This process is induced by a C3 hydrogen shift on the nitrogen atom. After opening of the cyclopropane, the dissociation of these complexes leads to m/z 44, 58, and 72 ions having [CH3(CH2)nCH NH2] structures. The mechanism of their formation is demonstrated by the MIKE spectra of 13C and deuterium labelled compounds. The experimental results are in good agreement with those described by Gross etal., who studied the fragmentation of the complexes formed during the reaction between substituted ionized cyclopropanes and ammonia in the gas phase.

Au–Ir nanoalloy nucleation during the gas-phase condensation: a comprehensive MD study including different effects

2018 ◽  
Vol 5 (6) ◽  
pp. 1445-1457 ◽  
Author(s):  
Mohsen Abbaspour ◽  
Hamed Akbarzadeh ◽  
Zahra Valizadeh
Keyword(s):  
Gas Phase ◽  
Experimental Results ◽  
Temperature And Pressure ◽  
Increasing Temperature ◽  
Good Agreement

The number of formed clusters and their size increases with the increasing temperature and pressure, which is in good agreement with the experimental results.

Observation of 13C rearrangement in [13C2]biphenylene formed from benzyne on pyrolysis of [1,6-13C2]phthalic anhydride and [2a,3-13C2]benzocyclobutenedione

1984 ◽  
Vol 37 (8) ◽  
pp. 1643 ◽  
Author(s):  
M Barry ◽  
RFC Brown ◽  
FW Eastwood ◽  
DA Gunawardana ◽  
C Vogel
Keyword(s):  
Mass Spectrometry ◽  
Sulfur Dioxide ◽  
Isotopic Composition ◽  
Gas Phase ◽  
Phthalic Anhydride ◽  
Carbon Skeleton ◽  
Hydrogen Shift ◽  
Thermal Elimination ◽  
A Minor

Examination of [13C2]biphenylene formed by gas phase pyrolysis of doubly labelled benzyne precursors shows that the principal pyrolytic process leads to overall 1,2→1,3 rearrangement of the C6H4 carbon skeleton either in an intermediate C7H4O before decarbonylation or in benzyne itself. A minor process involves an apparent 1,3-hydrogen shift. [1,2-13C2]Ethyne-1,2-diylbistrimethylsilane was acylated with 3-(2,5-dihydro-1,1-dioxothien- 2-yl)propanoyl chloride and the resulting ketone was desilylated to yield 5-(2,5-dihydro-1,l-dioxo-thien-2-yl)[1,2-13C2]pent-1-yn-3-one. Thermal elimination of sulfur dioxide and cyclization followed by dehydrogenation yielded [7,7a-13C2]-2,3-dihydro-1H-inden-1-one which was oxidized and dehydrated to give [3a,4-13C2]isobenzofuran-1,3-dione. This doubly labelled phthalic anhydride was diluted to approximately 5% 13C2 and the resulting material was converted via benzenediazonium- 2-carboxylate into biphenylene at 84�, and pyrolysed at 830� to yield biphenylene, and a sample diluted to 7.5% was converted into [2a,3-13C2]benzocyclobutenedione which was pyrolysed at 650�, 750� and 830� to yield further samples of biphenylene. The biphenylene samples were examined by mass spectrometry at 20 eV to determine their isotopic composition and by 13C n.m.r. spectroscopy to determine the distribution of labelling.

Isomérisation de l'ion phényl-2 oxétane protoné avant sa fragmentation en spectrométrie de masse

1981 ◽  
Vol 59 (6) ◽  
pp. 968-973 ◽  
Author(s):  
Henri Edouard Audier ◽  
Arielle Milliet ◽  
Margaret Mruzek ◽  
Jean Pierre Denhez ◽  
Pierre Dizabo ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Potential Energy ◽  
Chemical Ionization ◽  
Heterocyclic System ◽  
Experimental Results ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Energy Profile ◽  
Potential Energy Profile ◽  
Spectrométrie De Masse

Fragmentations of the phenyl-2 oxetane ion by chemical ionization mass spectrometry, and of some isomeric ions, have been studied using deuterated and 13C labelled compounds. The heterocyclic system of the protonated phenyl-2 oxetane ion is broken before fragmentation giving a hydroxylated carbocation which can isomerize by 1–2 or 1–3 hydride transfers. The protonated phenyl-3 propanal thus obtained eliminates a molecule of water and yields a protonated indene ion. The potential energy profile and the mechanism proposed are in agreement with the experimental results.

Diastereoisomeric proton-bound complexes of 1,5-diaza-cis-decalin in the gas phase

2009 ◽  
Vol 74 (2) ◽  
pp. 243-254 ◽  
Author(s):  
Jana Roithová
Keyword(s):  
Mass Spectrometry ◽  
Nitrogen Atom ◽  
Dft Calculations ◽  
Electrospray Ionization ◽  
Gas Phase ◽  
Energy Difference ◽  
Ion Pair ◽  
Collision Induced Dissociation ◽  
Chiral Effects

Diastereoisomeric proton-bound complexes of 1,5-diaza-cis-decalin (1) with butan-2-amine (2) are studied by means of the DFT calculations and mass spectrometry. The calculations reveal that 2 is bound via proton to only one nitrogen atom of the bicyclic base 1. The homochiral complex is favored by about 4 kJ/mol over the heterochiral complex. For a more loosely bound ion-pair complex [(1H)I(2H)]+ of the protonated bases 1 and 2 with an iodine counterion the energy difference drops to about 2 kJ/mol. Chiral effects in the formation of [(1)H(2)]+ are studied by the collision-induced dissociation of [(1H)I(2H)]+ generated by the electrospray ionization of the solution of [1·Cu(OH)I] and 2 in acetonitrile. The dominant fragmentation of [(1H)I(2H)]+ leads to 1·H+ and 2·HI, which is at small collision energies accompanied by the elimination of HI leading to the desired [(1)H(2)]+ ion. The chiral effect of 1.2 is determined in favor for the formation of the homochiral complex [(1)H(2)]+.

Hydrogen-shift isomerism: mass spectrometry of isomeric benzenesulfonate and 2-, 3- and 4-dehydrobenzenesulfonic acid anions in the gas phase

2005 ◽  
Vol 40 (8) ◽  
pp. 1064-1071 ◽  
Author(s):  
Julius Ben-Ari ◽  
Alex Etinger ◽  
Adrian Weisz ◽  
Asher Mandelbaum
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Hydrogen Shift

COMPUTER MODELING OF CHEMICAL EQUILIBRIUMS IN WO3–H2O SYSTEM

2017 ◽  
pp. 35-48 ◽  
Author(s):  
V.P. Bondarenko ◽  
O.O. Matviichuk
Keyword(s):  
Transition Temperature ◽  
Gas Phase ◽  
Single Phase ◽  
Reference Data ◽  
Maximum Amount ◽  
Reaction Products ◽  
Influence Of Temperature ◽  
Equilibrium Chemical ◽  
Program Data ◽  
Good Agreement

Detail investigation of equilibrium chemical reactions in WO3–H2O system using computer program FacktSage with the aim to establish influence of temperature and quantity of water on formation of compounds of H2WO4 and WO2(OH)2 as well as concomitant them compounds, evaporation products, decomposition and dissociation, that are contained in the program data base were carried out. Calculations in the temperature range from 100 to 3000 °С were carried out. The amount moles of water added to 1 mole of WO3 was varied from 0 to 27. It is found that the obtained data by the melting and evaporation temperatures of single-phase WO3 are in good agreement with the reference data and provide additionally detailed information on the composition of the gas phase. It was shown that under heating of 1 mole single-phase WO3 up to 3000 °С the predominant oxide that exist in gaseous phase is (WO3)2. Reactions of it formation from other oxides ((WO3)3 and (WO3)4) were proposed. It was established that compound H2WO4 is stable and it is decomposed on WO3 and H2O under 121 °C. Tungsten Oxide Hydrate WO2(OH)2 first appears under 400 °С and exists up to 3000 °С. Increasing quantity of Н2О in system leads to decreasing transition temperature of WO3 into both liquid and gaseous phases. It was established that adding to 1 mole WO3 26 mole H2O maximum amount (0,9044–0,9171 mole) WO2(OH)2 under temperatures 1400–1600 °С can be obtained, wherein the melting stage of WO3 is omitted. Obtained data also allowed to state that that from 121 till 400 °С WO3–Н2O the section in the О–W–H ternary system is partially quasi-binary because under these temperatures in the system only WO3 and Н2O are present. Under higher temperatures WO3–Н2O section becomes not quasi-binary since in the reaction products WO3 with Н2O except WO3 and Н2O, there are significant amounts of WO2(OH)2, (WO3)2, (WO3)3, (WO3)4 and a small amount of atoms and other compounds. Bibl. 12, Fig. 6, Tab. 5.

Explaining the magnetism of gold

2017 ◽  
Author(s):  
Robson de Farias
Keyword(s):  
Gas Phase ◽  
Computational Study ◽  
Formation Enthalpy ◽  
Gold Atom ◽  
Orbital Energy ◽  
Knudsen Effusion ◽  
Energy Diagram ◽  
Unpaired Electrons ◽  
The Difference ◽  
Good Agreement

<p>In the present work, a computational study is performed in order to clarify the possible magnetic nature of gold. For such purpose, gas phase Au<sub>2</sub> (zero charge) is modelled, in order to calculate its gas phase formation enthalpy. The calculated values were compared with the experimental value obtained by means of Knudsen effusion mass spectrometric studies [5]. Based on the obtained formation enthalpy values for Au<sub>2</sub>, the compound with two unpaired electrons is the most probable one. The calculated ionization energy of modelled Au<sub>2</sub> with two unpaired electrons is 8.94 eV and with zero unpaired electrons, 11.42 eV. The difference (11.42-8.94 = 2.48 eV = 239.29 kJmol<sup>-1</sup>), is in very good agreement with the experimental value of 226.2 ± 0.5 kJmol<sup>-1</sup> to the Au-Au bond<sup>7</sup>. So, as expected, in the specie with none unpaired electrons, the two 6s<sup>1</sup> (one of each gold atom) are paired, forming a chemical bond with bond order 1. On the other hand, in Au<sub>2</sub> with two unpaired electrons, the s-d hybridization prevails, because the relativistic contributions. A molecular orbital energy diagram for gas phase Au<sub>2</sub> is proposed, explaining its paramagnetism (and, by extension, the paramagnetism of gold clusters and nanoparticles).</p>

Inducing Frictional Force to Enhance the Transient Response in Beams

2019 ◽  
Vol 22 (2) ◽  
pp. 88-93
Author(s):  
Hamed Khanger Mina ◽  
Waleed K. Al-Ashtrai
Keyword(s):  
Numerical Analysis ◽  
Transient Response ◽  
Frictional Force ◽  
Damping Ratio ◽  
Experimental Results ◽  
Damping Capacity ◽  
Tightening Force ◽  
Contact Areas ◽  
Good Agreement ◽  
Ansys Workbench

This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.

Diffusion model for deposition of epitaxial GaAs layers prepared by the MOCVD method

1991 ◽  
Vol 56 (10) ◽  
pp. 2020-2029
Author(s):  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma ◽  
Rudolf Hladina
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Kinetic Model ◽  
Gas Phase ◽  
Substrate Surface ◽  
Deposition Process ◽  
Hydrogen Atmosphere ◽  
Epitaxial Gaas ◽  
Kinetics Of ◽  
Good Agreement

The authors proposed and treated quantitatively a kinetic model for deposition of epitaxial GaAs layers prepared by reaction of trimethylgallium with arsine in hydrogen atmosphere. The transport of gallium to the surface of the substrate is considered as the controlling process. The influence of the rate of chemical reactions in the gas phase and on the substrate surface on the kinetics of the deposition process is neglected. The calculated dependence of the growth rate of the layers on the conditions of the deposition is in a good agreement with experimental data in the temperature range from 600 to 800°C.

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