With the molecular composition of the resting-state complex established, we endeavored to determine the kinetic dependence on [1g]T and [10a] to elucidate the stoichiometry of the ratedetermining transition-state complex (Fig. ). The distinct infrared absorbance of the P=O bond in 3a (1240 cm -1 ) and the symmetric P-O stretch in 10a (1039 cm -1 ) provided excellent handles to monitor reaction progress by in situ IR spectroscopy. By systematically varying the concentration of 1g and applying Bures' normalized time scale treatment to the reaction profiles , we obtained excellent graphical overlay only when dividing the reaction profiles by [1g] n for n = 1, indicating that the reaction rate exhibits first-order dependence on catalyst [1g]T . Furthermore, the consumption of phosphonium species 10a and the formation of product 3a both follow a zerothorder kinetic rate behavior for the first ~80% of the reaction (Fig. ), consistent with a turnoverlimiting and enantiodetermining dealkylation transition state proceeding from a 1:1 1gꞏ10 restingstate complex.