Abstract Laser flash photolysis of p-CF 3 and p-Cl-phenylchloro diazirines produces the corresponding carbenes which react with acetone to produce easily detected ylids. The absolute rate constants of reaction of these carbenes with acetone, and the rate constants of reaction of the ylids with diethylfumarate have been determined. No reaction was found between these carbenes and simple esters or ethylene carbonate.
