Heats, equilibrium constants, and free energies of formation of the C3 to C5 diolefins, styrene, and the methylstyrenes

Abstract

For th e C3 to Cs diolefins, styrene, and the m ethylstyrenes, values are presented for t he followin g thermody namic prop er t ies to 1,500° K : H eat-conte nt fun ction, free-energy fun ction, entropy, heat conten t , hea t capacity, heat of forma tion from the clements, free energy of fonnatio n from t he elem ents, an d loga rit hm of the equilibrium constant of format ion from the elem ents. Equili brium con tants and concent rat ions are given in tabular and graphica l form for some reactions of isomerizat ion a nd dehydrogenat ion .

Enthalpy change for the s-trans and s-cis conformational equilibrium in 2-methyl-1,3-butadiene (isoprene), as studied by high-temperature ultraviolet absorption spectroscopy

“…On the basis of these tests and the statistical error of 0.10 kcal/mol, the overall error in AH°S19 is estimated as 0.15 kcal/mol. The final result for the enthalpy difference, AH°5i9, for the conformational equilibrium of isoprene (eq 1) is therefore AH°5l9 = 1.78 ± 0.15 kcal/mol This value is in good agreement with the value, 1.7 kcal/mol, derived from the early work of Kilpatrick et al 13 and with the value of 1.5 ± 0.3 kcal/mol due to Dzhessati et al,12 and is compatible with the more recent results of the electron diffraction study by Traetteberg and co-workers.5 It also is greater than the minimum value of 1.6-1.7 kcal/mol estimated from the work of Sheridan.8 However, it is substantially greater than the value of 1.1 kcal/mol reported by Compton et al7 and is 0.4-0.5 kcal/mol less than values derived from theoretical calculations.14 '16 Comparison with 1,3-Butadiene. For 1,3-butadiene, AH°S20 for s-trans to s-cis equilibrium was found to be 3.02 ± 0. kcal/mol.…”

“…Compton and co-workers7 also fitted thermodynamic data due to Kilpatrick et al 13 to the two-state model of eq 1. Although the accuracy was low, the value of AH0 obtained was about 1.7 kcal/mol.…”

Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy” Part II

“…Table 3. Experimental [23][24][25][26] and model data for a set of dienes. The first three species comprise isolated double bonds, the next six contain conjugated double bonds, and finally, the last four reveal cumulative double bonds.…”

Hydrocarbons for fuel - 75 years of materials research at NBS

“…The published calculations and correlations included: Gibbs energies and equilibria of isomerization of isomeric hydrocarbons [45], enthalpies, equilibrium constants, and Gibbs energies of formation of selected hydrocarbons as functions of temperature to 1000 or 1500 K [46] ; normal coordinate analyses [47] The presence of the resulting large amounts of numerical data on homologous series of compounds and compounds showing well defined compositional and structural variations, such as the isomeric forms, the presence of multiple bonds, and cyclization, has encouraged many individual attempts in NBS and elsewhere to devise correlations. Generally these correlations have as their primary goal s.ufficient understanding of the effects of these structural and compositional variations to permit estimation of the properties of other substances not measured.…”