Ring Conserved Isodesmic Reactions:  A New Method for Estimating the Heats of Formation of Aromatics and PAHs

2005 ◽  
Vol 109 (8) ◽  
pp. 1621-1628 ◽  
Author(s):  
R. Sivaramakrishnan ◽  
Robert S. Tranter ◽  
K. Brezinsky
Keyword(s):  
New Method ◽  
Heats Of Formation ◽  
Isodesmic Reactions

A Theoretical Study of Substituted Stepwise Fluorinated Cyclopropanone Keto-Enol System

2003 ◽  
Vol 58 (12) ◽  
pp. 749-755
Author(s):  
Abdullah El-Alali ◽  
Ali A. Marashdeh ◽  
Salim M. Khalil
Keyword(s):  
Theoretical Study ◽  
Dipole Moments ◽  
Heats Of Formation ◽  
Geometrical Parameters ◽  
Free Energies ◽  
Isodesmic Reactions ◽  
Orbital Energies ◽  
Substantial Concentration ◽  
Homo Lumo ◽  
Complete Optimization

MINDO-Forces calculations have been performed with complete optimization of the geometries on stepwise fluorinated cyclopropanones and their enols. Increase in the number of fluorine atoms causes destabilization of cyclopropanone. Perfluorinated enol was found to be present in substantial concentration, as was mentioned in previous work. This is supported by calculations of Gibbs free energies and isodesmic reactions. Geometrical parameters, heats of formation, electron densities, dipole moments and orbital energies (HOMO-LUMO) are reported.

MINDO-Forces Study on Substituted Nitromethane ⇋ aci-Nitromethane Tautomerism

2005 ◽  
Vol 60 (1-2) ◽  
pp. 47-53
Author(s):  
Bareehan M. Salim ◽  
Salim M. Khalil
Keyword(s):  
Theoretical Calculations ◽  
Geometry Optimization ◽  
Heats Of Formation ◽  
Geometrical Parameters ◽  
Free Energies ◽  
Electron Densities ◽  
Isodesmic Reactions ◽  
Complete Geometry Optimization

MINDO-Forces calculations with complete geometry optimization have been performed on nitromethane, aci-nitromethane and X-substituted nitromethane and aci-nitromethane (X = F, OH, NH2, CH3, CN, CF3, NO2, CHO). It is found that nitromethane is more stable than aci-nitromethane by 9.337 kcal/mol. This agrees with theoretical calculations. Thermodynamically, substituted aci-nitro tautomers are more stable than the corresponding nitromethane, except in case of the substituent F. Geometrical parameters, heats of formation, electron densities, Gibbs free energies and isodesmic reactions are reported.

Heats of vaporization of some monosubstituted cyclopropane, cyclobutane, and cyclopentane derivatives. Some observations on the enthalpies of isodesmic ring opening reactions of cyclobutane derivatives

1983 ◽  
Vol 61 (3) ◽  
pp. 503-505 ◽  
Author(s):  
Richard Fuchs ◽  
John H. Hallman
Keyword(s):  
Liquid State ◽  
Ring Opening ◽  
Methyl Ketone ◽  
Heats Of Formation ◽  
Isodesmic Reactions ◽  
Gaseous State ◽  
Ring Opening Reactions ◽  
Cyclobutane Derivatives ◽  
Heats Of Vaporization

The following heats of vaporization at 25 °C (ΔHv0) have been measured by vaporization calorimetry: cyclopropyl methyl ketone (39.41 ± 0.09 kJ mol−1). methyl cyclopropanecarboxylate (41.27 ± 0.06 kJ mol−1), cyclobutyl cyanide (44.34 ± 0.20 kJ mol−1), methyl cyclobutanecarboxylate (44.72 ± 0.09 kJ mol−1), ethylcyclobutane (31.24 ± 0.03 kJ mol−1), and cyclopentyl cyanide (48.12 ± 0.09 kJ mol−1). Values of ΔHv0 of the last four compounds have been combined with liquid state heats of formation to give new values of the gaseous state heats of formation (ΔHf(g)).When cyclobutyl cyanide, ethylcyclobutane, and cyclobutylamine are involved in hypothetical isodesmic reactions with ethane to give propane and isopropyl derivatives, the enthalpies of reaction are −102.1 ± 1.7 kJ mol−1 (−24.4 ± 0.4 kcal/mol), 8.3 kJ mol−1 (2.0 kcal/mol) less exothermic than the value for cyclobutane. Possible origins of this difference are discussed.

Density Functional Studies on the Standard Heats of Formation for Nitroaromatic Molecules

2015 ◽  
Vol 1095 ◽  
pp. 415-418
Author(s):  
Xin Fang Su
Keyword(s):  
Experimental Data ◽  
Density Functional ◽  
Heats Of Formation ◽  
Isodesmic Reaction ◽  
Computational Results ◽  
Reference Compound ◽  
Isodesmic Reactions ◽  
Functional Studies ◽  
Experimental Values

The standard heats of formation for 12 nitroaromatic molecules in gas at 298 K were calculated at B3P86/6-311G** levels using different isodesmic reactions. Comparison between the computational results and the experimental values reveals that using methane as reference compound to design isodesmic reaction is able to predict satisfactory results of heats of formation for ortho-substituted nitroaromatic molecules; however, using benzene as reference compound is able to give agreement with experimental data for meta-substituted and para-substituted nitroaromatic molecules.

Thermochemistry of conjugation of simple cyclopropane derivatives

1982 ◽  
Vol 60 (14) ◽  
pp. 1832-1835 ◽  
Author(s):  
Richard Fuchs ◽  
John H. Hallman ◽  
Michael O. Perlman
Keyword(s):  
Liquid State ◽  
Heats Of Formation ◽  
Isodesmic Reactions ◽  
Gaseous State ◽  
Heats Of Vaporization ◽  
Cyclopropane Derivatives

Heats of vaporization of cyclopropyl cyanide and cyclopropylbenzene have been measured by vaporization calorimetry, and combined with liquid state heats of formation to give gaseous state heats of formation. When these compounds, cyclopropane, 1,1-dimethylcyclopropane, and cyclopropylamine are involved in (hypothetical) isodesmic reactions with ethane to give the isopropyl derivative and propane, the enthalpies of reaction are −116.0 ± 1.3 kJ mol−1, except for cyclopropylbenzene (−103.7 kJ mol−1). The latter is less exothermic, in part, because of slight steric destabilization of the product, isopropylbenzene, but mainly due to 8 kJ mol−1 stabilization of cyclopropylbenzene, which is the only of these cyclopropyl derivatives showing appreciable thermochemical stabilization.

Selective Sampling and Orientation of Non-Homogeneous Tissues

1968 ◽  
Vol 26 ◽  
pp. 98-99
Author(s):  
C. C. Clawson ◽  
L. W. Anderson ◽  
R. A. Good
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Random Sampling ◽  
New Method ◽  
Microscope Examination ◽  
Small Areas ◽  
Selective Sampling ◽  
Large Numbers ◽  
Specific Orientation

Investigations which require electron microscope examination of a few specific areas of non-homogeneous tissues make random sampling of small blocks an inefficient and unrewarding procedure. Therefore, several investigators have devised methods which allow obtaining sample blocks for electron microscopy from region of tissue previously identified by light microscopy of present here techniques which make possible: 1) sampling tissue for electron microscopy from selected areas previously identified by light microscopy of relatively large pieces of tissue; 2) dehydration and embedding large numbers of individually identified blocks while keeping each one separate; 3) a new method of maintaining specific orientation of blocks during embedding; 4) special light microscopic staining or fluorescent procedures and electron microscopy on immediately adjacent small areas of tissue.

A new method for the determination of nitrates

1960 ◽  
Vol 23 ◽  
pp. 227-232 ◽  
Author(s):  
P WEST ◽  
G LYLES
Keyword(s):  
New Method
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