Radical telomerization of 1,3-butadiene with perfluoroalkyl iodides

The radical telomerization of 1,3-butadiene in the presence of 1-iodoperfluorohexane and 1-iodoperfluorooctane (RFI) is presented. Experimental parameters (such as the nature of the radical initiator, temperature, solvent and initial molar ratios of the reactants) were varied to increase both 1,3-butadiene and RFI conversions. Best conditions are reached at 140–150°C with di-tert-butyl peroxide as initiator and acetonitrile as solvent. According to different conditions, the monoadduct and higher order telomers were synthesized with average number molecular weights ranging from 250 to 4 000 as determined by 1H NMR spectroscopy and elemental analysis. 80% of the 1,4-adducts were noted to lack a terminal iodine atom. The transfer constant of RFI towards 1,3-butadiene was determined to be CT = 2.59 at 145°C which induces the formation of nonfunctional oligomers when a high [butadiene]0/[RFI]0 molar ratio was used.