Kinetic and mechanistic studies on the interaction of adenosine with hydroxopentaaquarhodium(III) ion

The kinetics of the title reaction have been studied spectrophotometrically as a function of pH, [substrate], [adenosine] and temperature (50-65°C) by monitoring the appearance of a characteristic peak of the adenosine substituted product (λ^sub max^ = 289 nm). The reaction rate is pH dependent in the 3.0-4.3 range. With increase in [adenosine] the rate was found to increase and approached a limit at a higher adenosine concentration. The following rate law has been established at pH 4.3: d[Rh(H^sub 2^O)^sub 3^(OH)(adenosine)^sup 2+^]/dt = k ^sub a^ K ^sub E^[Rh(H^sub 2^O)^sub 5^(OH)^sup 2+^]^sub total^[adenosine]/ (1 + K ^sub E^[adenosine]) Rate and activation parameters are consistent with an associative interchange mechanism. Experimental results are discussed with reference to literature data for analogous systems.[PUBLICATION ABSTRACT]