Thermochemistry of Organic and Heteroorganic Species. Part IX. Photoionization Studies of Isomerization and Fragmentation of Polysubstituted Cyclopropenes: Phenyl-Substituted Cyclopropenes

2000 ◽  
Vol 6 (1) ◽  
pp. 53-64 ◽  
Author(s):  
V.V. Takhistov ◽  
I.N. Domnin ◽  
D.A. Ponomarev
Keyword(s):  
Mass Spectrometry ◽  
Enthalpy Of Formation ◽  
Good Alternative ◽  
Enthalpies Of Formation ◽  
Isodesmic Reactions ◽  
Ion Structure ◽  
Photoionization Mass Spectrometry ◽  
General Methodology ◽  
Fragment Ions ◽  
The Enthalpy Of Formation

Ionization and appearance energies of some fragment ions from 1,2,3-trimethy1-3-phenyl-, 3-methyl-1,2,3-triphenyl-, 1,2-diphenyl-3-methoxycarbonyl-, 1,2,3-triphenyl-3-methoxycarbonyl- and 1,3,3-triphenyl-2-methoxycarbonyl-cyclopropenes were measured by photoionization mass spectrometry. It was shown that in none of these compounds did the fragment ions possess the expected stable substituted cyclopropenium ion structure. Accordingly, possible schemes of molecular ion isomerization are given. The enthalpies of formation of nearly 50 substituted cyclopropenium ions, and ions of related structure, were estimated using series of isodesmic reactions. This publication, together with the previous works of the authors in this Journal, demonstrates the general methodology for estimation of the enthalpy of formation for even-electron ions. It is suggested that the present methodology can provide a good alternative to other estimation or computation procedures applied to the thermochemistry of ions.

scholarly journals Point Defects in Materials Part I: Behavior and Characteristics in Different Material Classes

MRS Bulletin ◽  
1991 ◽  
Vol 16 (11) ◽  
pp. 28-32
Author(s):  
David N. Seidman ◽  
Donglu Shi
Keyword(s):  
Enthalpy Of Formation ◽  
Point Defects ◽  
Theoretical Calculations ◽  
Pure Copper ◽  
Historical Review ◽  
Enthalpies Of Formation ◽  
Professor Emeritus ◽  
Face Centered Cubic ◽  
Interstitial Atoms ◽  
The Enthalpy Of Formation

In this issue of the MRS Bulletin we present five papers that involve point defect phenomena in a wide variety of materials—metals, conducting ceramic oxides, semiconductors, amorphous alloys, and high Tc superconducting oxides. The unifying theme of this issue is point defects—zero-dimensional defects. Even for the high Tc oxides, where planar defects are discussed, it is the ordering of oxygen/vacancy chains that ultimately gives rise to twins in the famous YBa2Cu3O7.δ (1:2:3) oxide superconductor.Hillard Huntington, professor emeritus of physics at Rensselaer Polytechnic Institute, is an early and important pioneer in the study of point defects in metals. A theorist, he has also performed many experiments over the years; for example, he performed key early experiments on electromigration effects. Huntington's article presents a historical review of the research on vacancies and self-interstitial atoms in metals during the period that stretches from the mid-1930s to the mid-1960s. He played a crucial role in this field as a result of his seminal theoretical calculations, with Fred Seitz in 1942, on the enthalpies of formation and migration of vacancies or self-interstitial atoms in pure copper. Huntington's and Seitz's calculations indicated that diffusion occurs predominantly by a monovacancy mechanism since the enthalpy of formation of a self-interstitial atom, the [100] split form, also called the dumbbell form, is too large to be compatible with the activation enthalpy for self-diffusion in copper. It is now well established that the latter is given by the sum of the enthalpy of formation and the enthalpy of migration of a monovacancy in many face-centered-cubic (fcc), body-centered-cubic (bec), and hexagonal-close-packed (hcp) metals.

scholarly journals Thermochemistry of Eight Membered Ring Hydrocarbons. The Enthalpy of Formation of Cyclooctane

2001 ◽  
Vol 71 (3) ◽  
pp. 507-515
Author(s):  
Daniela Gheorghe ◽  
Ana Neacsu ◽  
Stefan Perisanu
Keyword(s):  
Differential Scanning Calorimetry ◽  
Liquid Phase ◽  
Phase Change ◽  
Enthalpy Of Formation ◽  
Membered Ring ◽  
Heat Of Combustion ◽  
Enthalpies Of Formation ◽  
Scanning Calorimetry ◽  
Solid Liquid ◽  
The Enthalpy Of Formation

A new value of the enthalpy of formation of cyclooctane (-156.2�1.2 kJ mol-1) based on heat of combustion measurements is reported. Its solid - liquid phase change was investigated by differential scanning calorimetry in both directions revealing an overcooling effect of over 23 K. Our enthalpy of formation of cyclooctane was used together with literature values of heats of hydrogenation of 8 carbon atoms cycloolefins to calculate the enthalpies of formation of the later. The strain energies of the investigated molecules were calculated and discussed.

Photoionenspektroskopie an Schwefelchloridpentafluorid SF5Cl, das Ionisationspotential von Schwefelpentafluorid SF5/Photoion Spectroscopy of Sulfurchloridepentafluoride SF5Cl, the Ionization Potential of Sulfurpentafluoride SF5

1989 ◽  
Vol 44 (1) ◽  
pp. 21-23 ◽  
Author(s):  
H. Baumgärtel ◽  
H .-W. Jochims ◽  
E. Rühl ◽  
O. Lösking ◽  
H. Willner
Keyword(s):  
Mass Spectrometry ◽  
Energy Range ◽  
Ionization Potential ◽  
Photoionization Mass Spectrometry ◽  
Fragment Ions

Abstract The appearance potentials of fragment ions from SF5Cl have been measured in the energy range 12 - 20 eV by means of photoionization mass spectrometry. From these data, the ionization potential of SF5 comes to 9.65 eV.

Enthalpies of formation of LaBO3perovskites (B = Al, Ga, Sc, and In)

2003 ◽  
Vol 18 (10) ◽  
pp. 2501-2508 ◽  
Author(s):  
Jihong Cheng ◽  
Alexandra Navrotsky
Keyword(s):  
High Temperature ◽  
Enthalpy Of Formation ◽  
Solution Calorimetry ◽  
Tolerance Factor ◽  
Enthalpies Of Formation ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide ◽  
First Time ◽  
The Enthalpy Of Formation

Enthalpies of formation from constituent oxides and elements at 298 K were determined by high-temperature oxide melt solution calorimetry for a group of technologically important perovskites LaBO3(B = La, Ga, Sc, and In). Enthalpies of formation from oxides of LaAlO3and LaGaO3are −69.61 ± 3.23 kJ/mol and −52.39 ± 1.99 kJ/mol, respectively. The data were consistent with literature values obtained using other methods. The enthalpies of formation of LaScO3and LaInO3from oxides were reported for the first time as −38.64 ± 2.30 kJ/mol and −23.99 ± 2.31 kJ/mol, respectively. As seen for other perovskites, as the tolerance factor deviates more from unity (in the order Al, Ga, Sc, In), the enthalpy of formation from oxides becomes less exothermic, indicating a less stable structure with respect to the constituent oxides.

Structural Characterization of Phosphatidylcholines by Atmospheric Pressure Photoionization Mass Spectrometry

2005 ◽  
Vol 11 (4) ◽  
pp. 409-417 ◽  
Author(s):  
Arnaud Delobel ◽  
David Touboul ◽  
Olivier Laprévote
Keyword(s):  
Mass Spectrometry ◽  
Structural Analysis ◽  
Atmospheric Pressure ◽  
Fatty Acyl ◽  
Ionization Mechanism ◽  
Atmospheric Pressure Photoionization ◽  
Photoionization Mass Spectrometry ◽  
Fragment Ions ◽  
Acyl Chains

The potential of atmospheric pressure photoionization was investigated for the structural analysis of phosphatidylcholine lipids (PCs). [M+H]+ ions of high abundance were obtained, along with several fragment ions. Three of these dissociation products corresponded to quite unusual fragmentation pathways but allowed the determination of both the nature and the position on the glycerol backbone ( sn-1 or sn-2) of the fatty acyl chains. The loss of a methyl group from the choline head was also observed. These results suggest a complex ionization mechanism in atmospheric pressure photoionization. However, this method proved to be very powerful for the rapid structural analysis of PC species without using tandem mass spectrometry experiments.

Calorimetric determination of the enthalpy of formation of InN and comparison with AlN and GaN

2001 ◽  
Vol 16 (10) ◽  
pp. 2824-2831 ◽  
Author(s):  
M. R. Ranade ◽  
F. Tessier ◽  
A. Navrotsky ◽  
R. Marchand
Keyword(s):  
Enthalpy Of Formation ◽  
Standard Enthalpy ◽  
Sodium Molybdate ◽  
Solution Calorimetry ◽  
Large Error ◽  
Area Measurement ◽  
Enthalpies Of Formation ◽  
Standard Enthalpy Of Formation ◽  
Straight Line ◽  
The Enthalpy Of Formation

The standard enthalpy of formation of InN at 298 K has been determined using high-temperature oxidative drop solution calorimetry in a molten sodium molybdate solvent at 975 K. Calorimetric measurements were performed on six InN samples with varying nitrogen contents. The samples were characterized using x-ray diffraction, chemical analysis, electron microprobe analysis, and Brunauer–Emmett–Teller surface area measurement. The variation of the enthalpy of drop solution (kJ/g) with nitrogen content is approximately linear. The data, when extrapolated to stoichiometric InN, yield a standard enthalpy of formation from the elements of ?28.6 ± 9.2 kJ/mol. The relatively large error results from the deviation of individual points from the straight line rather than uncertainties in each set of data for a given sample. This new directly measured enthalpy of formation is in good agreement with the old combustion calorimetric result by Hahn and Juza (1940). However, this calorimetric enthalpy of formation is significantly different from the enthalpy of formation values derived from the temperature dependence of the apparent decomposition pressure of nitrogen over InN. A literature survey of the enthalpies of formation of III–N nitride compounds is presented.

A low-temperature technique for measuring enthalpies of formation

1996 ◽  
Vol 11 (6) ◽  
pp. 1403-1409 ◽  
Author(s):  
T. P. Weihs ◽  
T. W. Barbee ◽  
M. A. Wall
Keyword(s):  
Low Temperature ◽  
Enthalpy Of Formation ◽  
Enthalpies Of Formation ◽  
Scanning Calorimetry ◽  
Free Standing ◽  
Metal Compounds ◽  
Si Substrates ◽  
Multilayer Foils ◽  
Formation Enthalpies ◽  
The Enthalpy Of Formation

A technique to accurately measure the formation enthalpies of transition metal compounds at relatively low temperatures using thick multilayer foils and differential scanning calorimetry is demonstrated. The enthalpy of formation of Cu51Zr14 was measured using 25 μm thick, free-standing Cu–Zr multilayer foils. The multilayers were deposited onto Si substrates using a planetary, magnetron source sputtering system. They were removed from their substrates, cut into 6 mm diameter specimens, and scanned in temperature from 50 °C to 725 °C in a differential scanning calorimeter. Three distinct exothermic reactions were systematically observed. The heats from the first two reactions were summed and then analyzed using a simple model that accounts for interfacial reactions and heat losses during deposition. The enthalpy of formation for Cu51Zr14 was measured to be 14.3 ± 0.3 kJ/mol. This quantity agrees with the single value of ΔHf = 14.07 ± 1.07 kJ/mol reported in the literature for this Cu–Zr compound. The advantages of measuring formation enthalpies using thick multilayer foils and low temperature calorimetry are discussed.

Thermodynamics of metal-ligand bond formation. XI. Adducts of heterocyclic bases with copper(II) complexes of fluorinated β-diketones

1974 ◽  
Vol 27 (4) ◽  
pp. 741 ◽  
Author(s):  
DP Graddon ◽  
WK Ong
Keyword(s):  
Enthalpy Of Formation ◽  
Benzene Solution ◽  
Bidentate Ligand ◽  
Molecular Structures ◽  
Enthalpies Of Formation ◽  
Complex Forms ◽  
Heterocyclic Bases ◽  
The Enthalpy Of Formation ◽  
Metal Ligand ◽  
Ligand Bond

Thermodynamic data have been obtained for the reaction in benzene solution of copper(11) complexes of hexafluoropentanedione and three trifluorinated α-diketones with several unidentate and bidentate heterocyclic bases and terpyridine. With pyridine the hexafluoro� complex forms very stable 1 : 1 and 1 : 2 adducts. The enthalpy of adduct formation (-ΔH) is about 39 kJ mol-1 for the addition of each molecule of pyridine, about 10 kJ mol-1 more than for the formation of the 1 : 1 adduct with the acetylacetone complex. The trifluoro complexes form only 1 : 1 adducts with enthalpy of formation about 31 kJ mol-1 ; these are much more stable than Cu(acac)2(py), but the extra stability is mainly due to entropy factors. With bipyridine and phenanthroline all four fluoro complexes form very stable 1 : 1 adducts with enthalpies of formation about twice those for addition of one molecule of pyridine; this shows that two Cu-N bonds are formed. 2,9-Dimethyl-1,l0-phenanthroline forms a similar adduct, but the enthalpy of formation is much less, due to steric interference. Terpyridine forms a 1 : 1 adduct of much lower stability, probably behaving as an ortho-substituted bidentate ligand. Infrared spectra of the adducts of Cu(tfaa)2 and Cu(hfaa)2 support molecular structures in which one of the Cu-O bonds linking each β-diketone is lengthened to allow the formation of a strong pair of Cu-N bonds.

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