Simultaneous determination of relative and absolute rate constants in racemization studies; applications to kinetic isotope effects

The method reported allows the simultaneous determination of relative and absolute rate constants for two substances in a single kinetic run. The approach is of special interest for kinetic isotope effect determinations where rate ratios are often near one and failure to exactly duplicate reaction conditions can lead to uncertainties in the values calculated from independently measured rate constants. For racemization studies, using two optically active materials with opposite signs of rotation, knowing their initial rotational contribution and having the faster racemizing one in higher concentration, the rates can be calculated if the times required to reach zero net rotation and the extremum value are measured. Other systems to which the method can be extended are suggested.