Rates and Equilibria of the Reactions of Tertiary Phosphanes and Phosphites with Benzhydrylium Ions
- 18 January 2005
- journal article
- research article
- Published by Wiley in Chemistry – A European Journal
- Vol. 11 (3) , 917-927
- https://doi.org/10.1002/chem.200400696
Abstract
The kinetics of the reactions of benzhydrylium ions and quinone methides with eight tertiary phosphanes and two phosphites were investigated photometrically. The nucleophilicity parameters N and slope parameters s of these nucleophiles were derived according to the equation log k20 °C = s(N + E). Correlations of the nucleophilicity parameters N with pKHa and σp values as well as with the rate constants of reactions with other electrophiles are discussed. In some cases, equilibrium constants for the formation of phosphonium ions were measured, which allow one to determine the Marcus intrinsic barriers of ΔG0≠ = 58 kJ mol−1 for the reactions of triarylphosphanes with benzhydrylium ions. The N parameters [5.51 for P(OPh)3, 10.36 for P(OBu)3, 14.33 for PPh3, 15.49 for PBu3, 18.39 for P(4‐Me2NC6H4)3] are compared with the reactivities of other classes of nucleophiles (see, www.cup. uni‐muenchen.de/oc/mayr).Keywords
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