STRUCTURE-PROPERTY RELATIONSHIPS OF FLUOROOLEFINS——A SPECIAL SOLVENT EFFECT IN FREE-RADICAL ADDITIONS

The regioselectivity of the addition (R-values) of cyclopropyl radicals to fluoroolefinshas been found to be solvent-dependent In the present work, with vinylidene fluoride asthe substrate, the R-values are measured in fifteen solvents at 80℃.The results definitelyestablish that the regioselectivity R is dependent on the nature of the solvent. Interestingly,there is no correlation between the R-values and any of the known solvent polarity para-meters. Rather, the present result implicates that there might be a subtle "geometry factor"in operation. One possible rationalization for our results could be something like the following: in theprocess of nonelastic dynamic collision and packing of the liquid molecules, a "geometryfactor" of some solvents somehow discriminates between the two ends of the substrate mole-cule or the two corresponding transition states of addition. In order to test such a hypo-thetical idea, R-values are determined for variously proportioned binary mixtures. and the inter-relationship of the R-values of these binary solvent mixtures and the molar ratio of thetwo solvents is derived on the basis of this hypothesis. Experimental data are consistent withthe values thus calculated.