Intramolecular kinetic isotope effect in hydride transfer from dihydroacridine to a quinolinium ion. Rejection of a proposed two-step mechanism with a kinetically significant intermediate |
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Authors: | Perrin Charles L Zhao Chen |
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Institution: | Department of Chemistry, University of California, San Diego La Jolla, California 92093-0358, USA. cperrin@ucsd.edu |
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Abstract: | The intramolecular kinetic isotope effect (KIE) for hydride transfer from 10-methyl-9,10-dihydroacridine to 1-benzyl-3-cyanoquinolinium ion has been found to be 5-6 by both (1)H NMR and mass spectrometry. This KIE is consistent with other hydride transfers. It is inconsistent with the high intermolecular KIEs derived by fitting to a two-step mechanism with a kinetically significant intermediate complex, and it is inconsistent with the strong temperature dependence of those KIEs. We therefore reject the two-step mechanism for this reaction, and we suggest that other cases proposed to follow this mechanism are in error. |
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