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 (kovr), and associated activation parameters of the reaction were determined. Copyright © 2015 John Wiley & Sons, Ltd.