RELATIVE THERMODYNAMIC STABILITIES OF ALLYL VINYL AND PROPENYL VINYL ETHERS

The relative thermodynamic stabilities of a number of isomeric allyl v inyl and propenyl vinyl ethers were determined by chemical equilibrati on in DMSO solution with KOBu-t as catalyst. From the temperature depe ndence of the values of the equilibrium constant the parameters Delta G(m)(theta), Delta H-m(theta), and Delta S-m(theta) of isomerization a t 298.15 K were evaluated. Propenyl vinyl ethers, owing to their low e nthalpy contents, are much more stable than the isomeric allyl vinyl e thers. It appears that in the parent propenyl vinyl ether, the Me grou p attached to C-beta of the divinyl ether skeleton has a strong stabil izing effect, comparable to that of alkyl groups in ordinary olefins, on the unsaturated system. In more heavily alkyl-substituted divinyl e thers, however, the stabilizing effects of alkyl groups are less promi nent, being comparable to the low stabilization energies of alkyl grou ps in vinyl ethers, and depend moreover, on the pattern of substitutio n.