The effects of different ligands on the catalytic activity of the propykne polymerization catalyzed by o-XC6H4OTiCl3/MgCl2-EB systems (where X =-CH3

-H

-Cl and -NO2 respectively; EB stands for ethyl benzoate) were studied. It was found that the pKa value of o-XC6H4OH is greafer

the catalytic activity of corresponding catalytic system is higher. The reduction rate of o-CH3C6H5OTiCl3 is faster than that of o-ClC6H5OTiCl3 by AlEt3 Thus

it leads to a higher initial concentration of the active center in O-CH3C6H5OTiCl3/.MgCl2-EB than that in o-ClC6H4OTiCl3/MgCl2-EBsystem. Using tritiated alcohol quench-ing method

the concentrations of active center and the rete constants of propagation in abo-ve systems were also evaluated. The results obtained were consistent with the conclusions be-fore mentioned.