مرکز منطقه ای اطلاع رساني علوم و فناوري -

چكيده لاتين :

Kinetics of radical telomerization of vinyl acetate (VAc) with CDCI3 as a telogen in the presence of AIBN initiator was studied by 1H NMR. Structure of the chains was analyzed in detail by 1H NMR spectroscopy technique. It was observed that two telomers with different a-ends including trichloromethyl-and dichloromethyl-terminated VAc telomers were formed during the telomerization reaction. Therefore, two different mechanisms of the transfer reaction to CDCI3 telogen have been proposed which were supported in details by the abstraction of either deuterium or chlorine radicals from CDCI3 molecules. 1H NMR analysis also allowed us to calculate the conversionofVAc(XVAc)יnumber-averagedegree ofpolymerization(DPn),telomerpercentage (%), and the ratio of the abstractions of deuterium radicals to chlorine radicals (Ro/d from CDCI3 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 Ro and decreasing of the reaction temperature. Moreover, at the same conversion, telomer percentage increased by decreasing [AIBN]o and reaction temperature while decreased by decreasing of the Ro (or equivalently [CDCI3]) . The highest yield of telomer was about 60%. There was not any significant difference between the RO/e l at various conditions used in VAc telomerization by CDCI3. 1H NMR analysis showed that the rate of the abstraction of deuterium radical from CDCI3 molecule is favoured relative to its rate of chlorine radical abstraction.