THE REACTIVITY AND THE RING-OPENING REACTION-MECHANISM FOR VARIOUS SUBSTITUTED ACID ANHYDRIDES OF EPOXIDE ANHYDRIDE REACTION

The curing reaction of the epoxidized soybean oil (internal epoxide) with substituted phthalic anhydrides and maleic anhydrides was studied using tertiary amine as accelerator. The purpose was to elucidate the substituent effects (inductive, resonance, and steric) on the reactivity of acid anhydrides to epoxides. The reactivity of anhydrides was increased by the presence of electron attractive groups (Cl, NO2) as substituents. In the presence of an electron donating group (CH3), the reactivity of anhydrides depended on the position of substituents. Namely, the reactivity of 4-methylphthalic anhydride increased a little, whereas that of 3-methylphthalic anhydride decreased. The reactivity of anhydrides was much more affected by the steric hindrance, which results from the position of substituent, than by the inductive effect (I effect) of substituents. The reactivity appeared to be governed by the structure of the carboxyl anion which was formed from the ring-opening reaction. In the curing reaction of diglycidyl ether of bisphenol A (DGEBA) (external epoxide) with substituted phthalic anhydrides, the rate-determining step was the ring-opening reaction (zero-order reaction), and almost no recognizable difference was observed in the reactivity of anhydrides. The ring-opening reaction mechanism of anhydride was also examined.