ORGN 24 |
| In-Sook Han Lee and Young Ran Ji. Department of Science Education, Kangwon National University, Chunchon, 200-701, South Korea |
| Rate and equilibrium constants have been determined spectrophotometrically for the reactions of a series of 1-substituted benzyl-3-carbamoyl-1,4-dihydropyridine with a benzimidazolium ion (BI+), a benzothiazolium ion (BT+) and a benzoxazolium ion (BO+) in a solvent consisting of 4 parts of 2-propanol and one part of water at 25 oC. Reduction potentials for the oxidants (BI+, BT+, and BO+) have been estimated by assuming that the K's would be the same and accepting -361 mV as the reduction potential of 1-benzyl-3-carbamoylpyridinium ion. The oxidants give linear Bronsted plots with the slopes, alphas, respectively. The alpha values vary systematically with the spontaneity of the reactions. Within the modified Marcus theory the present system presents the evidence of a parallel (Leffler-Hammond) effect on the Bronsted alpha. These results rationalize the one-step mechanism of hydride transfer without the intervention of high-energy intermediate. |
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Physical Organic Chemistry: Calculations, Mechanisms, Photochemistry and High Energy Species
8:00 AM-12:00 PM, Sunday, September 7, 2003 Sheraton New York -- Royal Ballroom A, Oral
Division of Organic Chemistry |