ChemInform Abstract: OXYGEN-18 SCRAMBLING REACTION OF AROYL ALKYL CARBONATES

Specifically 18O-labeled p-substituted benzoyl cyclohexyl carbonates (1) were prepared and heated at 45, 70 and 75°C, and novel stepwise oxygen scrambling was found to take place in 1. On being heated at 45°C, the carbonic carbonyl oxygen atom and the oxygen atom sandwiched between the two carbonyl carbon atoms of 1 were found to scramble. The 18O-scrambling among the above two and carboxylic carbonyl oxygen atoms of 1 was found to take place at 70 or 75°C. A good first order kinetic dependence was observed for the first step of the scrambling at 45°C but no substituent effect. An intramolecular mechanism involving two steps of equilibration is proposed.