Kinetic Isotope Effects in Mixed Solvents

To calculate the mixed solvent isotope effect on rate constants one applies simple ideas from transition state theory to evaluate the isotope effect on the 

For the A-l mechanism the transition state involves only one hydrogen and the ratio of rate constants follows analogously from Equation (11.67) 

It is obvious from the discussion that one can take advantage of equations of the type (11.69), and its generalization to multiple sites, to deduce information about the number of protons actively participating in the transition state, see Fig. 11.7. 

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Formaldehyde reacts with nitrosobenzene (PhNO) to yield iV-phenylformohydrox-amic acid, PhN(OH)CHO. The primary kinetic isotope effect in mixed solvents is altered on addition of small amounts of salt, an effect also seen in water at higher salt concentrations, suggesting the involvement of chloride ion in C-H bond breaking. 

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