Structure and reactivity of α,β-unsaturated ethers. XIII. Cationic copolymerization and acid-catalyzed hydrolysis of 1,2-dialkoxyethylenes

The cationic copolymerizations of geometrical isomers of 1,2-dimethoxy- and 1,2-diethoxyethylenes with vinyl isobutyl ether as a reference monomer have been carried out in methylene chloride at ?70° using boron trifluoride etherate as catalyst. The kinetics of the acid-catalyzed hydrolysis of these ethers has also been investigated in 80% aqueous dioxane, in order to compare the results with the polymerizabilities. It has been found that the cis ethers are ca. four times as reactive as their trans isomers in both reactions. On the other hand, it has been proved that a β-alkoxyl substitution reduces the hydrolysis reactivity of vinyl alkyl ethers by a factor of ca. 10^?3 while it even enchances the cationic polymerizability. These contrasting results are interpretable from the nature of the transition states which are different for the two reactions.