Artículos de revistas
Conformer dipole moment and syn-1,3-diaxial steric effect on the conformational equilibrium of the cis isomer of some 1,3-disubstituted cyclohexanes
Registro en:
Journal Of Molecular Structure. Elsevier Science Bv, v. 743, n. 41699, n. 69, n. 72, 2005.
0022-2860
WOS:000229412200008
10.1016/j.molstruc.2005.02.028
Autor
de Oliveira, PR
Rittner, R
Institución
Resumen
The theoretical values of the dipole moment for the diaxial (ax-ax) conformer are larger than for the eq-eq conformer of some cis-3-halocyclohexanols (halo=Cl, Br and I) and c, S-3-halo-1-methoxycyclohexanes (halo=F, Cl, Brand 1). The experimental (3)J(HH) Coupling constants are rather large (> 10 Hz) indicating that the diequatorial (eq-eq) conformer is predominant for all compounds in the solvents studied. Dipole moments and NMR data lead to the conclusion that the conformational. equilibra of these 1,3-derivatives are not controlled by the solvent polarity, as is observed for the 1,2-disubstituted cyclohexanes, but are dictated by the syn-1,3-diaxial steric effect, which predominates over stabilization of the ax-ax conformer by an intramolecular hydrogen bond (IAHB). © 2005 Elsevier B.V. All rights reserved. 743 41699 69 72