Kinetics and Mechanism of the pyridinolysis of Ethyl Y-phenyl Chlorophosphates in Acetonitrile

초록

The kinetics and mechanism of the pyridinolysis (X-C5H4N) of enthyl ethyl Y-phenyl chlorophosphates (C2H4O(Y-C6H4O)P(=O)CI) are inverstingated at 35.0℃ in acetonitrile. The Hammett plots for substituent (Y) variations in the substrate (log k2 vs δY) exhibit a convex downward and concave upward biphasic type with breaks at Y = m-CH3. For electron-donating Y group the Hammett coefficents, pY, are large positive to positive to negative via about X = H (δx = 0) and cross-interaction constant XY is positive. positive. In the other hand for electron withdeawing Y groups pY values are large negative to positive through around X = H (δx = 0) with a negative XY value. These results are interpreted to indicate a two-stwp mechanistic parhway with a trigonal bipyramidal penta-coordinated intermediate (TBP-5C) via rate determining step change at the break-point (pY = 0) with a conformational changes in the TS. The unusual behaviors of phosphoryl transfer reactions known and we are intended to interpret and explain the phosphorus compounds.