ORGN 474 |
| The coalescence temperature for the room temperature magnetically non-equivalent methyl groups in the title compounds was determined via variable temperature NMR. The experimental ΔG* for the inversion of groups on nitrogen was calculated from the Eyring equation. Geometries, equilibrium geometries and the molecular orbital energies were calculated using Gaussian 98 software. Experimental and calculated values were consistent with the hypothesis that electronic effects alter the ΔG* for the inversion of groups on the imino nitrogen. Electron withdrawing groups lower the ΔG* by minimizing the lone pair interactions in the transition state while electron donating groups cause the opposite effect. Molecular orbital plots using the graphics module of the Spartan Software V.5.0 showed that, in the minimum energy conformation, the N-phenyl group prefers to be conjugated with the lone pair rather than the pi electrons of the imine chromophore. Further confirmation of the hypothesis results from the fact that the ΔG* for N-group inversion for N-p-toluosulfonyl group on the cyclobutanone was greater than that observed for the same group inversion on the 1,1-dichloroderivative. R= phenyl, p-methylphenyl, p-nitrophenyl, N-p-toluosulfonyl and N-p-toluosulfonyl-1,1 dichloro derivative
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New Reactions, Methodology, Total Synthesis, Physical Organic Chemistry
8:00 PM-10:00 PM, Tuesday, 15 March 2005 Convention Center -- Sails Pavilion, Poster
Sci-Mix
Division of Organic Chemistry |
