Conformational analysis of 1-acetyl-2-methylhydrazine

The conformational analysis of 1-acetyl-2-methylhydrazine was performed usi ng DNMR spectroscopy and quantum chemical calculations (B3LYP/6-31+G*, AM1 and PM3). Activation barrier for interconversion of Z and E conformers was measured to be 16.1 kcal/mol by DNMR. DFT calculations indicate that there are four minima on the 1-acetyl-2-methylhydrazine potential energy surface and the most stabile is Z conformer with the hydrogen bond between carbonyl group oxygen and hydrogen at non-an-dde nitrogen. The amide nitrogen was f ound to be close to planar in minima but strongly pyramidalized in TS. The activation barriers calculated at B3LYP/6-31+G* level of theory were in goo d agreement with experimentally measured one. AM1 method with molecular mec hanics correction gave potential energy surface in reasonable agreement wit h DFT results, but the activation energies were strongly underestimated. PM 3 method was found to give unsatisfactory results for conformational. analy sis of 1-acetyl-2-methylhydrazine. (C) 2001 Elsevier Science B.V. All right s reserved.