The Radical Addition Reaction of Esters to Hexafluoropropene

Abstract

γ-Ray induced addition reaction of 19 kinds of esters to hexafluoropropene was carried out as a part of studies on synthetic aspects of free-radical addition to fluoroolefins. Esters RCOOR' (R, R' -=CH₃, CH₂CH₃, CH₂CH₂CH₃, CH(CH₃)₂, CH₂CH₂CH₂CH₃, CH₂CH(CH₃)₂ ), [1a-j], gave in considerable yields the corresponding 1: 1 adducts which c onsisted of several isomeric esters carrying a fluoroalkyl-side chain at different positions. The ratios of isomers of the 1: 1 adducts indicated the following trends of apparent addition reactivities of the carbon atoms in an ester molecule: (1 ) -CH>>CH₂ >-CH₃, ( 2 ) the carbons in the alkoxyl group (R'O) were more reactive than those in the acyl group (RCO), and ( 3 ) the carbons with increased distance from the carbonyl group showed much increased reactivities. The last two trends, ( 2 ) and ( 3 ), were opposite to those reported in radical addition reactions of esters to alkenes. Whereas diethyl carbonate [1r] reacted similarly, esters containing an electronegative group RCOOCH₂CH₂ (R=CH₂F, CHClF, CH₂Cl, CHCl₂, CCl₃, CH₂CN, C₆H₅), [1k-q], either gave the 1: 1 adducts in much lower yields or gave no adducts at all, suggesting that the electro negative groups decrease reactivity for addition. γ-Butyrolactone [1 / s] gave no adduct.