Radical telomerization of 3,3,3-trifluoropropene with diethyl hydrogen phosphonate: Characterization of the first telomeric adducts and assessment of the transfer constants

The radical telomerization of 3,3,3-trifluoropropene (TFP) with diethyl phosphate (or diethyl hydrogen phosphonate, DEHP) was investigated to synthesize fluorinated telomers bearing a phosphonate end-group, as H(TFP)nP(O)(OEt)2. Di-tert-butyl peroxide was the most efficient radical initiator. A careful structural study of typical TFP/DEHP telomers was performed by 1H, 19F, and 31P nuclear magnetic resonance spectroscopies. These analytical methods allowed us to prove the selective addition of the phosphonyl radical onto the hydrogenated side of TFP, while the telomers containing more than two TFP units were composed of TFP isomers containing normal and reversed adducts. The kinetics of telomerization led to the assessment of the first four order transfer constants giving an infinite transfer constant of 0.75 at 140 °C for DEHP.