Structural and Mechanistic Studies of Telomerization of Vinyl Acetate by CDCl3 via 1H NMR

Kinetics of radical telomerization of vinyl acetate (VAc) with CDCl3 as a telogenin the presence of AIBN initiator was studied by 1H NMR. Structure of the chainswas analyzed in detail by 1H NMR spectroscopy technique. It was observed that two telomers with different α-ends including trichloromethyl- and dichloromethyl-terminated VAc telomers were formed during the telomerization reaction. Therefore, two different mechanisms of the transfer reaction to CDCl3 telogen have been proposed which were supported in details by the abstraction of either deuterium or chlorine radicals from CDCl3 molecules. 1H NMR analysis also allowed us to calculate the conversion of VAc (XVAc), number-average degree of polymerization (DPn), telomer percentage (%), and the ratio of the abstractions of deuterium radicals to chlorine radicals (RD/Cl) from CDCl3 molecules. These results showed that at the same conversion, at first, DPn decreases with increase of the initial concentration of AIBN but then increases. Also, DPn at the same conversion decreases by increasing of the R0 and decreasing of the reaction temperature. Moreover, at the same conversion, telomer percentage increased by decreasing [AIBN]0 and reaction temperature while decreased by decreasing of the R0 (or equivalently [CDCl3]). The highest yield of telomer was about 60%. There was not any significant difference between the RD/Cl at various conditions used in VAc telomerization by CDCl3. 1H NMR analysis showed that the rate of the abstraction of deuterium radical from CDCl3 molecule is favoured relative to its rate of chlorine radical abstraction.