Figure 1

The reaction rate data shown in Figure 1 are typical of the solvent effects we have seen in these studies. This figure compares the solvent effect on rate of carvone hydrogenation using homogeneous Wilkinson's catalyst, Wilkinson's catalyst anchored onto alumina using either PTA or STA as the anchoring agent and the commercially available polystyrene supported Wilkinson's catalyst. These reactions were stopped after one equivalent of hydrogen was taken up so they represent the rate of formation of dihydro-carvone.

It can be seen that the solvent has virtually no effect on those reactions run using the homogeneous catalyst but has a fairly significant effect on the heteropoly anchored species. The commercially available phosphinated polystyrene supported material is relatively inactive with the solvent used having only a slight effect on the rate of reaction. The solid catalysts were used several times and the rates are the average of these various reactions. Also measured was the effect of solvent on the amount of Rh lost in each of those reactions run using a solid catalyst.

Figure 2

Fig. 2 shows the ppm of Rh found in the first reaction mixture for each solvent and catalyst. Thus, this number represents the maximum amount of Rh in these reaction mixtures. It can be seen that the maximum amount of loss is found with the solvents in which the reaction is the slowest. Further, the polystyrene material shows significant Rh loss.