Abstract: The mechanism of the addition reactions Si-or P-centered radicals to diethyl 2-butenedioate has been studied by ESR method.Si-or P-centered radicals could be added to diethyl maleate which possesses cis-configuration.Hypertine splitting constants of the silyl radical adducts linked with different substituents were measured in our experiments. Radical polymerization of diethyl fumarate which possessetrans-configuration was initiated by radical Bu¹O·and produeed telomer or polymer. The addition reactions of Si-or P-centered radicals to diethyl fumarate could not happen due to steric hindranee.

Key words: Si-centered radical, P-centered radical, Diethyl maleate, Diethyl fumarate, Kadical addition reaction, ESR