Enthalpies of formation of radicals and the mass spectra of the products of tetrafluoroethylene polymerization in acetone

摘要

The mass spectra of the dissociative electron-impact ionization products of telomers formed upon the radiation-chemical telomerization of tetrafluoroethylene in acetone were measured over the range of m/z from 1 to 204. The most intense bands at m/z = 43, 51, and 57 were attributed to the CH_3CO~+, CF_2H~+ and CH_3COCH_2~+ cations-the main dissociation products of the H(C_2F_4)_nCH_2COCH_3 telomers. The telomer composition was consistent with a radical telomerization mechanism, in which chain growth and chain transfer are due to the formation of the CH_3COCH_2~· radical. Based on published data supplemented with quantum-chemical calculations, the enthalpies of formation of the radicals R(CF_2)_n (n = 2-8; R = H, CH_3, CH_3CO, and CH_3COCH_2) were tabulated. The formation of telomers with the same terminal groups is consistent with thermodynamic data and a polymerization mechanism in which the chain growth reaction is diffusion-limited and the chain transfer reaction is activated hydrogen-atom transfer.