To begin, we used the experimentally determined pseudo-first order rate constants for each model which were obtained using UV-vis experiments (Supplementary Figure ). By implementing the existence of intermediate species based on the mechanism of the nucleophilic substitution through P-salt intermediates proposed by Krische and coworkers (Figure -I), we found good agreement (R 2 = 0.89 -0.97) between the model and our experimental data (Figure ). We noticed, however, that the model overestimated the TPPTS release at a later stage in the reaction, which becomes more pronounced with increasing SH concentrations.