What Other Data Are There

We admit to comparatively little experience in quantitatively understanding solvent and entropic effects. For example, consider the 1,2,3,4-tetramethylbutadienes presented in Table 2. From Reference 23, we find the relative solution phase Gibbs energies for the ( , )-, (E,Z)- and (Z,Z)-isomers (34-36, respectively) increase in the order (E,E) (E, Z) (Z, Z). By contrast, the gas phase enthalpies of formation increase in the order (Z,Z) (E,E) (E,Z). Somehow it seems inappropriate to include the other C8H14 hydrocarbons of Reference 23 in the current study when we only know their relative Gibbs energies in solution.  

Data are sparse. Let us thus relax the earlier phase restriction to the gas phase. We therefore briefly discuss some conjugated dienes for which we have enthalpy of formation data solely in the condensed phase. The first pair of species are the isomeric (Z,Z)-and 

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