STANDARD HEATS OF FORMATION OF 2,2-DIMETHOXYPROPANE (l), AND 2,2-DIETHOXYPROPANE (l). GROUP ADDITIVITY THEORY AND CALCULATED HEATS OF FORMATION OF FIVE KETALS

1962 ◽  
Vol 66 (1) ◽  
pp. 97-99 ◽  
Author(s):  
J. H. Stern ◽  
F. H. Dorer
Keyword(s):  
Heats Of Formation ◽  
Group Additivity ◽  
Additivity Theory

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.

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.

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