Small (Poly)Unsaturated Oxygen Containing Ions and Molecules: A Brief Assessment of Their Thermochemistry Based on Computational Chemistry

2009 ◽  
Vol 15 (2) ◽  
pp. 261-273 ◽  
Author(s):  
John L. Holmes ◽  
Karl J. Jobst ◽  
Johan K. Terlouw
Keyword(s):  
Large Deviations ◽  
Computational Chemistry ◽  
Excellent Agreement ◽  
Radical Cations ◽  
Heat Of Formation ◽  
Heats Of Formation ◽  
Group Additivity ◽  
Neutral Species ◽  
Brief Assessment ◽  
Theory And Experiment

The CBS-QB3, CBS-APNO and Gaussian-3 model chemistries have been used to determine the ionic and neutral heats of formation and the adiabatic ionization energies ( IEa) derived therefrom, for the ca 30 principal isomers of the C3H2O•+ and the C4H4O•+ families of radical cations. Theory and experiment are in excellent agreement for those molecules whose experimental IEa has been accurately measured. In contrast, large deviations from the computed values were found for a great many ionic heats of formation reported in the literature. These deviations largely arise from the uncertainty in the heat of formation of the corresponding neutral species for which often only a rough estimate is available. A useful by-product of this study is that it permits the evaluation of new Benson-type group additivity ( GA) terms appropriate for highly unsaturated oxygen containing molecules. Several new GA terms are proposed but it is also argued that a single GA term for the ketene function cannot be defined.

Computation of linear elastic properties from microtomographic images: Methodology and agreement between theory and experiment

Geophysics ◽  
2002 ◽  
Vol 67 (5) ◽  
pp. 1396-1405 ◽  
Author(s):  
Christoph H. Arns ◽  
Mark A. Knackstedt ◽  
W. Val Pinczewski ◽  
Edward J. Garboczi
Keyword(s):  
Elastic Properties ◽  
Excellent Agreement ◽  
Fontainebleau Sandstone ◽  
Linear Elastic ◽  
Numerical Predictions ◽  
Wide Range ◽  
Digitized Images ◽  
Water Saturated ◽  
Dry Water ◽  
Theory And Experiment

Elastic property‐porosity relationships are derived directly from microtomographic images. This is illustrated for a suite of four samples of Fontainebleau sandstone with porosities ranging from 7.5% to 22%. A finite‐element method is used to derive the elastic properties of digitized images. By estimating and minimizing several sources of numerical error, very accurate predictions of properties are derived in excellent agreement with experimental measurements over a wide range of the porosity. We consider the elastic properties of the digitized images under dry, water‐saturated, and oil‐saturated conditions. The observed change in the elastic properties due to fluid substitution is in excellent agreement with the exact Gassmann's equations. This shows both the accuracy and the feasibility of combining microtomographic images with elastic calculations to accurately predict petrophysical properties of individual rock morphologies. We compare the numerical predictions to various empirical, effective medium and rigorous approximations used to relate the elastic properties of rocks to porosity under different saturation conditions.

Radial Flow Between Axisymmetric Nonparallel Plates of Small Slope

1988 ◽  
Vol 110 (2) ◽  
pp. 342-346
Author(s):  
R. F. Gans ◽  
A. G. Johnson ◽  
S. B. Malanoski
Keyword(s):  
Excellent Agreement ◽  
Mass Flux ◽  
Radial Flow ◽  
Central Pressure ◽  
Axially Symmetric ◽  
Air Mass ◽  
Bearing Load ◽  
Dramatic Difference ◽  
Theory And Experiment

We have measured the separation and central pressure of a slightly concave axially symmetric pressurized bearing as a function of lubricant (air) mass flux and bearing load. We find that a mean face slope of 1.6 × 10−3 makes a dramatic difference in the behavior of the bearing, reducing the central pressure by more than a factor of two and eliminating the need for overpressures to start the system. We have also explored the behavior of the system analytically and find excellent agreement between theory and experiment.

Sulfenic acids in the gas phase. Preparation, ionization energies and heats of formation of methane-, ethene-, and benzenesulfenic acid

1988 ◽  
Vol 53 (9) ◽  
pp. 2140-2158 ◽  
Author(s):  
František Tureček ◽  
Libor Brabec ◽  
Tomáš Vondrák ◽  
Vladimír Hanuš ◽  
Josef Hájíček ◽  
...  
Keyword(s):  
Experimental Data ◽  
Gas Phase ◽  
Radical Cations ◽  
Appearance Energy ◽  
Heats Of Formation ◽  
Ionization Energies ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Mndo Calculations ◽  
Sulfenic Acids

Methane-, ethene-, and ethynesulfenic acids were generated in the gas phase by flash-vacuum pyrolysis of the corresponding tert-butyl sulfoxides at 400 °C and 10-4 Pa. Benzenesulfenic acid was prepared from phenyl 3-buten-1-yl sulfoxide at 350 °C and 10-4 Pa. The sulfenic acids were characterized by mass spectrometry Threshold ionization energies (IE) were measured as IE(CH3SOH) = 9·07 ± 0·03 eV, IE(CH2=CHSOH) = 8·70 ± 0·03 eV, IE(HCCSOH) = 8·86 ± 0·04 eV, and IE(C6H5SOH) = 8·45 + 0·03 eV. Radical cations [CH3SOH].+, [CH2=CHSOH].+, and [HCCSOH].+ were generated by electron-impact-induced loss of propene from the corresponding propyl sulfoxides and their heats of formation were assessed by appearance energy measurements as 685, 824, and 927 kJ mol-1, respectively. Heats of formation of the neutral sulfenic acids and the S-(O) (C), S-(O) (Cd), S-(O) (Ct) and S-(O) (CB) group equivalents were determined. The experimental data, supported by MNDO calculations, point to sulfenate-like structures (R-S-OH) for the sulfenic acids under study.

Heats of vaporization and gaseous heats of formation of some five- and six-membered ring alkenes

1979 ◽  
Vol 57 (17) ◽  
pp. 2302-2304 ◽  
Author(s):  
Richard Fuchs ◽  
L. Alan Peacock
Keyword(s):  
Gas Chromatography ◽  
Double Bond ◽  
Heat Capacities ◽  
Membered Ring ◽  
Heats Of Formation ◽  
Group Additivity ◽  
Liquid Heat ◽  
Heats Of Vaporization

The heats of vaporization of 1-methylcyclopentene, 3-methylcyclopentene, ethylidenecyclopentane, 1-ethylcyclopentene, methylenecyclohexane, allylcyclopentane, vinylcyclohexane, ethylidenecyclohexane, allylcyclohexane, 3,3-diethylpentane, 2,2,4,4-tetramethylpentane, and trans-2,2,5,5-tetramethyl-3-hexene have been measured by the gas chromatography – calorimetry method. These values have been combined with previously reported liquid heats of formation to give gaseous values of ΔHf. The results indicate that the internal double bond is favored by about 0.5 kcal over the exo in both 5- and 6-membered rings, but the endo–exo differences are much smaller than previously believed. Several of the liquid heat capacities that were measured were not well predicted by group additivity schemes.

Diazen und andere Distickstoffhydride: Bildungswärmen, Dissoziationsenergien, Auftrittspotentiale, Protonenaffinitäten [1] / Diazene and other Dinitrogen Hydrides: Heats of Formation, Dissoziation Energies, Appearance Potentials, Proton Affinities [1]

1979 ◽  
Vol 34 (10) ◽  
pp. 1385-1390 ◽  
Author(s):  
Nils Wiberg ◽  
Gerd Fischer ◽  
Heinz Bachhuber
Keyword(s):  
Hydrogen Atom ◽  
Proton Affinity ◽  
Heat Of Formation ◽  
Heats Of Formation ◽  
Proton Affinities ◽  
Kcal Mole ◽  
Energy Data

AbstractIonisation and appearance potentials were obtained for diazene HN = NH (prepared by thermolysis of TOSN2H2M, M = Li, Na, K), isodiazene H2N = N (prepared by thermolysis of TOSN2H2CS and N2H4 microwave radiolysis, respectively), and other hydrides N2Hn (cf. Table I). The following energy data (kcal/mole) have been determined for diazene: heat of formation (32), enthalpy of isomerisation to isodiazene (13), NN-dissoziation energy (122), NH-dissoziation energy (81), hydrogen atom affinity (45), proton affinity (176).

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