On the Interpretation of Deuterium Kinetic Isotope Effects in CH Bond Functionalizations by Transition‐Metal Complexes

Rate versus selectivity determining: The measurement of a kinetic isotope effect (KIE) can provide valuable information about the mechanism of a reaction, but care must be taken in the design and interpretation of KIE experiments. Depending on the experiment that is conducted, the observation of a primary KIE resulting from H/D substitution does not necessarily imply that CH bond cleavage occurs during the rate-determining step of a reaction. FG=functional group.