Rhodium complexes entropy effects

The rate ratio analysis must also account for entropy effects associated with the limited mobility of the substrate relative to the active site within the polymer. Roucls and Ekerdt (16) measured the relative rates for hydrogenation of cyclooctene and cyclohexene over an immobilized rhodium complex and found that the rate for cyclooctene was less than that for cyclohexene for the homogeneous rhodium complex, RhCl(PPh3)3, and in 1, 2, and 3 X dlvlnylbenzene polystyrene resins. Furthermore, they found that the relative rate differed with dlvlnylbenzene content. The relative rates were shown to be intrinsic rate ratios (16). Roucls and Ekerdt proposed that sterlc constraints due to the presence of the polysier support in the vicinity of active rhodium affected activity. All the rhodium sites were exposed to the same substrate concentration the sites displayed a different Inherent activity toward the two substrates. 

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