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.
Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13 (Haus F), 81377 München (Germany), Fax: (+49) 89-2180-77717.
Dorothea
D
Richter
Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13 (Haus F), 81377 München (Germany), Fax: (+49) 89-2180-77717.
Yue
Y
Tan
Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13 (Haus F), 81377 München (Germany), Fax: (+49) 89-2180-77717.
Anna
A
Antipova
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.
Xiao-Qing
XQ
Zhu
Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13 (Haus F), 81377 München (Germany), Fax: (+49) 89-2180-77717.
Herbert
H
Mayr
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