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Rates and Equilibria of the Reactions of Tertiary Phosphanes and Phosphites with Benzhydrylium Ions
Author(s) -
Kempf Bernhard,
Mayr Herbert
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400696
Subject(s) - nucleophile , chemistry , electrophile , phosphonium , medicinal chemistry , reaction rate constant , ion , kinetics , equilibrium constant , computational chemistry , inorganic chemistry , organic chemistry , catalysis , physics , quantum mechanics
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 k 20 °C = s ( N + E ). Correlations of the nucleophilicity parameters N with p K Ha and σ p 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 Δ G 0 ≠ = 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 PPh 3 , 15.49 for PBu 3 , 18.39 for P(4‐Me 2 NC 6 H 4 ) 3 ] are compared with the reactivities of other classes of nucleophiles (see, www.cup. uni‐muenchen.de/oc/mayr).