Isomer group thermodynamics

Alberty, R. A., and I. Oppenheimer, A Continuous Thermodynamics Approach to Chemical Equilibrium Within an Isomer Group, /. Chem. Phys., 81, 4603 (1984). 

In this chapter we will find that when isomers are in chemical equilibrium, it is convenient to treat isomer groups like species in order to reduce the number of terms in the fundamental equation. We will also discuss the effect of ionic strength and temperature on equilibrium constants and thermodynamic properties of species. More introductory material on the thermodynamics of chemical reactions is provided in Silbey and Alberty (2001). 

Alberty, R, A., Extrapolation of standard chemical thermodynamic properties of alkene isomers groups to higher carbon numbers, J. Phys. Chem 87,4999 (1983). 

Natural Variables Legendre Transforms Isomer Group Thermodynamics Gibbs-Duhem Equation References... 

R. A. Alberty, Chemical thermodynamic properties of isomer groups, I EC Fund. 22,218-321 (1983). 

When a vinyl group is conjugated to an aromatic ring, coordination is thermodynamically favored outside the aromatic system. In contrast, when a pendant acetyl group is present, the thermodynamic isomer often involves coordination of the aromatic system. For polycyclic aromatic systems, the metal favors the coordination site that minimizes the loss of aromatic stabilization. Thus,... 

R. A. Alberty and C. A. Gehrig, Standard chemical thermodynamic properties of alkane isomer groups , J. Phys. Chem. Ref. Data, 13,1173 (1984). Tabulations of C°, S°, AfH° and Af G° for 0 < T (K) < 1500 for alkanes with 10 or fewer carbons. Also tabulated are group contributions and equilibrium fractions within alkane isomer groups. The values are updated from the study by D. W. Scott (1974). 

Alberty, R. A. and Reif, A. K. (1988). Standard chemical thermodynamic properties of polycyclic aromatic hydrocarbons and their isomer groups, 1, benzene series. Journal of physical and chemical reference data, 17, pp. 241-253. 

Azoles containing a free NH group react comparatively readily with acyl halides. N-Acyl-pyrazoles, -imidazoles, etc. can be prepared by reaction sequences of either type (66) -> (67) or type (70)->(71) or (72). Such reactions have been carried out with benzoyl halides, sulfonyl halides, isocyanates, isothiocyanates and chloroformates. Reactions occur under Schotten-Baumann conditions or in inert solvents. When two isomeric products could result, only the thermodynamically stable one is usually obtained because the acylation reactions are reversible and the products interconvert readily. Thus benzotriazole forms 1-acyl derivatives (99) which preserve the Kekule resonance of the benzene ring and are therefore more stable than the isomeric 2-acyl derivatives. Acylation of pyrazoles also usually gives the more stable isomer as the sole product (66AHCi6)347). The imidazole-catalyzed hydrolysis of esters can be classified as an electrophilic attack on the multiply bonded imidazole nitrogen. 

Electrocyclic reactions of 1,3,5-trienes lead to 1,3-cyclohexadienes. These ring closures also exhibit a high degree of stereospecificity. The ring closure is normally the favored reaction in this case, because the cyclic compound, which has six a bonds and two IT bonds, is thermodynamically more stable than the triene, which has five a and three ir bonds. The stereospecificity is illustrated with octatrienes 3 and 4. ,Z, -2,4,6-Octatriene (3) cyclizes only to cw-5,6-dimethyl-l,3-cyclohexadiene, whereas the , Z,Z-2,4,6-octa-triene (4) leads exclusively to the trans cyclohexadiene isomer. A point of particular importance regarding the stereochemistry of this reaction is that the groups at the termini of the triene system rotate in the opposite sense during the cyclization process. This mode... 

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