Kinetics of hydride abstractions from 2-arylbenzimidazolines.
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 degrees C. The reactions follow second-order kinetics, and the corresponding rate constants k2 obey the linear free energy relationship log k2(20 degrees 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 C--H hydride donors which have so far been parameterized. The poor correlation between the rates of the hydride transfer reactions and the corresponding hydricities (DeltaH0) indicates variable intrinsic barriers.
Richter
Dorothea
D
Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13 (Haus F), 81377 München (Germany), Fax: (+49) 89-2180-77717.
Tan
Yue
Y
Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13 (Haus F), 81377 München (Germany), Fax: (+49) 89-2180-77717.
Antipova
Anna
A
Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13 (Haus F), 81377 München (Germany), Fax: (+49) 89-2180-77717.
Zhu
Xiao-Qing
XQ
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Weijin Road, No 94, 300071 Tianjin (P.R. China), Fax: (+86) 22-2349-9184.
Mayr
Herbert
H
Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13 (Haus F), 81377 München (Germany), Fax: (+49) 89-2180-77717.
D000097:Acetonitriles / Q000737:chemistry*; D001562:Benzimidazoles / Q000737:chemistry; D001880:Boranes / Q000737:chemistry*; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D005492:Folic Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015394:Molecular Structure; D013696:Temperature; D013816:Thermodynamics
D000097:Acetonitriles; D001562:Benzimidazoles; D001880:Boranes; D005492:Folic Acid; C031000:benzimidazole; C032159:acetonitrile