Phase equilibrium energy attributed

Theoretical work by the groups directed by Sustmann and, very recently, Mattay attributes the preference for the formation of endo cycloadduct in solution to the polarity of the solvent Their calculations indicate that in the gas phase the exo transition state has a lower energy than the endo counterpart and it is only upon introduction of the solvent that this situation reverses, due to the difference in polarity of both transition states (Figure 1.2). Mattay" stresses the importance of the dienophile transoid-dsoid conformational equilibrium in determining the endo-exo selectivity. The transoid conformation is favoured in solution and is shown to lead to endo product, whereas the cisoid conformation, that is favoured in the gas phase, produces the exo adduct This view is in conflict with ab initio calculations by Houk, indicating an enhanced secondary orbital interaction in the cisoid endo transition state . 

The methods of measurement of the surface energy of liquids may be divided into two classes the static and dynamic methods. In general for pure unassociated liquids in contact with their vapour alone the values of the surface energy determined by the two methods do not differ beyond the range which may be attributed to experimental error. In other cases, however, marked divergence between the values obtained by the two methods is to be noted. This divergence is, as we shall have occasion to note, due to the comparatively slow rate of attainment by diffusion of equilibrium in the surface phase of solutions. 

At one time it was believed that the entropy of polymer solutions followed approximately the ideal laws and the non ideal character was attributed to energy effects. Consider now the distribution of macromolecules over two liquid phases, for instance two non-miscible liquids. Designating one of the phases by a stroke, and introducing the subscript r for the polymer molecules, the equilibrium requires that... 

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