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Kinetics of Hydride Abstractions from 2‐Arylbenzimidazolines
Author(s) -
Richter Dorothea,
Tan Yue,
Antipova Anna,
Zhu XiaoQing,
Mayr Herbert
Publication year - 2009
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200900322
Subject(s) - hydride , nucleophile , parameterized complexity , chemistry , acetonitrile , kinetics , reaction rate constant , medicinal chemistry , thermodynamics , computational chemistry , mathematics , physics , organic chemistry , hydrogen , combinatorics , catalysis , quantum mechanics
The rates of the hydride abstractions from the 2‐aryl‐1,3‐dimethyl‐benzimidazolines 1a – f by the benzhydrylium tetrafluoroborates 3a – e were determined photometrically by the stopped‐flow method in acetonitrile at 20 °C. The reactions follow second‐order kinetics, and the corresponding rate constants k 2 obey the linear free energy relationship log k 2 (20 °C)= s ( N + E ), from which the nucleophile‐specific parameters N and s of the 2‐arylbenzimidazolines 1a – c have been derived. With nucleophilicity parameters N around 10, they are among the most reactive neutral CH hydride donors which have so far been parameterized. The poor correlation between the rates of the hydride transfer reactions and the corresponding hydricities (Δ H 0 ) indicates variable intrinsic barriers.