Resumen

BASSO, Ernani A.; OLIVEIRA, Paulo R.; CAETANO, Josiane  y  SCHUQUEL, Ivânia T. A.. Semiempirical and ab initio calculations versus dynamic NMR on conformational analysis of cyclohexyl-N,N-dimethylcarbamate . J. Braz. Chem. Soc. [online]. 2001, vol.12, n.2, pp. 215-222. ISSN 0103-5053.  http://dx.doi.org/10.1590/S0103-50532001000200015.

Axial-equatorial conformational proportions for cyclohexyl-N,N-dimethyl carbamate have been measured, for the first time, by the Eliel method, ¹H and ¹³C dynamic nuclear magnetic resonance (DNMR). The results were compared against those determined by theoretical calculations. By the Eliel method at least five experimentally independent measureables were used in CCl₄, CDCl₃ and CD₃CN. The ¹H and ¹³C low temperature experiments were performed in CF₂Br₂/CD₂Cl₂ . Semiempirical methods MNDO, AM1 and PM3 and ab initio molecular orbital calculations at the HF/STO-3G and HF/6-31G(d,p) levels have been performed on the axial and equatorial conformers populations. All applied methods correctly predict the equatorial conformer preference over the axial one. The resulting equatorial preferences determined by NMR data and theoretical calculations are in good agreement.

Palabras llave : conformational analysis; theoretical calculations; cyclohexane derivative; dynamic NMR.