CARBON KINETIC ISOTOPE EFFECTS AND TRANSITION STRUCTURES IN THE REARRANGEMENTS OF ALLYL VINYL ETHERS - 2-(TRIMETHYLSILOXY)-3-OXA-1,5-HEXADIENE AND 2-(METHOXYCARBONYL)-3-OXA-1,5-HEXADIENE

C-14 KIE (kinetic isotope effects) were measured for the C-1, C-2, C-4 , and C-6 positions in the rearrangement of 2-(trimethylsiloxy)- (1a) and 2-(methoxycarbonyl)-3-oxa-1,5-hexadiene (1b). The data, along with earlier C-4 and C-6 deuterium KIE, were fitted to Bebovib modeling ca lculations. The calculations show that in the transition structure (TS ) for 1a 70-80% bond breaking and 20% of bond making occurs, whereas i n the TS of 1b both bond breaking and bond making amount to 30-40%. Re sults for 1a and 1b are compared with earlier results for the parent c ompound, allyl vinyl ether.