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Nucleophilicities and Carbon Basicities of Pyridines
Author(s) -
Brotzel Frank,
Kempf Bernhard,
Singer Thomas,
Zipse Hendrik,
Mayr Herbert
Publication year - 2006
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.200600941
Subject(s) - nucleophile , chemistry , electrophile , pyridine , aqueous solution , reactivity (psychology) , carbon fibers , ion , reaction rate constant , medicinal chemistry , computational chemistry , organic chemistry , inorganic chemistry , catalysis , kinetics , mathematics , physics , alternative medicine , pathology , algorithm , quantum mechanics , composite number , medicine
Rate and equilibrium constants for the reactions of pyridines with donor‐substituted benzhydrylium ions have been determined spectrophotometrically. The correlation equation log k (20 °C)= s ( N + E ), in which s and N are nucleophile‐specific parameters and E is an electrophile‐specific parameter, has been used to determine the nucleophilicity parameters of various pyridines in CH 2 Cl 2 and aqueous solution and to compare them with N of other nucleophiles. It is found that the nucleophilic organocatalyst 4‐(dimethylamino)pyridine (DMAP) and tertiary phosphanes have comparable nucleophilicities and carbon basicities despite widely differing Brønsted basicities. For that reason, these reactivity parameters are suggested as guidelines for the development of novel organocatalysts. The Marcus equation is employed for the determination of the intrinsic barriers of these reactions.