Using microwave irradiation decreased remarkably the reaction
times. So, to further optimize the reaction conditions, the temperature
and the MW power were also optimized and the best results
were obtained using 0.1 g of nano-g-Fe2O3eSO3H in solvent-free
condition at 250 W. In both methods, 60
C was the optimum
temperature. No increase in yield was observed at higher temperatures,
while lowering the temperature below 60
C reduced the
reaction rate.