Kinetic spectrophotometric approach to the reaction mechanism of pyrrole phosphorus ylide formation based on monitoring the zwitterionic intermediate by using the stopped‐flow technique

For the first time, an experimental evidence for the existence of a zwitterionic intermediate (ZI) on reaction mechanism of a synthesized phosphorous ylide has been presented in aqueous–organic solvent mixtures by using the stopped‐flow technique. Spectral analyses confirmed the existence of ZI in the step 1 of the reaction. The step 1 that was recognized as a fast step included the formation and decay of the ZI. Pro‐K analyzer detected six species according to the proposed mechanism. Also, the kinetics of the reaction has been studied by the UV–Vis spectrophotometer. The value of rate constants for the step 1 (k₁ and k_?1), step 2 (k₂) and overall (k_ovr), and associated activation parameters of the reaction were determined. Copyright © 2015 John Wiley & Sons, Ltd.