RATE ENHANCEMENT OF ORGANIC-REACTIONS BY MICROWAVES AT ATMOSPHERIC-PRESSURE

Several different reactions have been studied to determine whether the y occur more rapidly than conventionally heated reactions at atmospher ic pressure. Small rate enhancements have been observed for some react ions carried out under microwave reflux in a modified domestic microwa ve oven. The Knoevenagel reaction of acetophenone with ethyl cyanoacet ate was shown to have a rate enhancement of 2.5 times. However this re action showed no rate increase over conventional heating, at the same temperature, in a variable-frequency microwave oven. It is therefore p robable that the small rate enhancements observed in these experiments , using microwave heating, were due to hot spots or superheating of th e solvent rather than to nonthermal effects.