ORGN 300 |
| Eric Noe, Dalephine E. Davis, and Diwakar M Pawar. Department of Chemistry, Jackson State University, Jackson, MS 39217 |
| The 1H NMR spectrum of a 5% sample of triphenylmethyl formate in acetone-d6 showed peaks for the formyl protons at 8.63 ppm for the E and 8.43 ppm for the Z at -105.3°C. Free-energy barriers for Z-to-E and E-to-Z conversions were determined to be 8.92 and 8.69 kcal/mol, respectively, at -93.4°C by lineshape matching. Ab initio calculations were carried out, and at the HF/6-31G* level, the E conformation was calculated to be 0.38 kcal/mol higher in free energy than the Z, and a Z-to-E free-energy barrier of 6.30 kcal/mol was calculated. Free-energy barriers to rotation about the bond between oxygen and the triphenylmethyl group were also calculated. The 13C NMR spectrum of a 1% sample of N-triphenylmethyl formamide in 50:50 CH2Cl2/CD2Cl2 showed two carbonyl peaks at 166.1 ppm (E) and 160.6 ppm (Z). The 1H spectrum showed two doublets for the formyl protons. The doublet from the formyl proton cis to the NH proton (Z conformation) had a smaller coupling constant and absorbed at lower field strength than the trans formyl proton of the E conformation. A population of 37.4% was found for the Z conformation for a 1% solution in CH2Cl2/CD2Cl2. |
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Physical Organic, Combinatorial, Materials, Molecular Recognition
8:00 PM-10:00 PM, Tuesday, March 30, 2004 Anaheim Convention Center -- Hall A, Poster
Division of Organic Chemistry |