Chapter 15 - Rhodium catalyzed homogeneous hydroformylation of unsaturated compounds in supercritical carbon dioxide

Abstract

This chapter investigates the rhodium catalyzed homogeneous hydroformylation of unsaturated compounds in supercritical carbon dioxide. A novel catalyst, HRh (CO) [P (p-CF3C6H4)3]3, was synthesized for homogeneous catalytic hydroformylation of unsaturated compounds in supercritical carbon dioxide. The incorporation of para-trifluoromethyl groups to the conventional hydroformylation catalyst, HRh (CO) [P (C6H5)3]3, provided enhanced solubility in supercritical carbon dioxide while maintaining catalyst activity. The substrates 1-octene, 1-decene, 1,7-octadiene, styrene, allylbenzene, trans-2-octene, 2-methyl-1-heptene, and cyclohexene were hydroformylated at 50°C and 273 atm. The rates and selectivities were observed for various substrates under standard reaction conditions. Selectivities were found to be similar to those for the conventional catalyst in organic solvents. Initial rates were calculated from the linear portion of each rate curve by estimating the slope in mol dm–3 min–1. The reaction rates for compounds with unsubstituted terminal double bonds were more than an order-of-magnitude higher than for compounds with substituted or internal double bonds. Furthermore, the reaction rate for cyclohexene was an additional order-of-magnitude lower than for 2-octene, whereas 1-octyne was not converted at all.