Dataset for: Probing long-range spin-spin coupling constants in 2-halo-substituted cyclohexanones and cyclohexanethiones: the role of solvent and stereoelectronic effects
2018-06-21T14:20:32Z (GMT) by
Earlier studies with 2-bromocyclohexanone demonstrated a measurable long-range coupling constant (4JH2,H6) for the equatorial conformer, while 4JH2,H4 and 4JH4,H6 were not observed; as a consequence, it is inferred that the carbonyl group plays an important role particularly due to hyperconjugative interactions C2H2→*C=O and C6H6→*C=O. In the present study, NBO analysis and coupling constant calculations were performed to cyclohexanone and cyclohexanethione alpha substituted with F, Cl and Br, aiming to evaluate the halogen effect and acceptor character of the π* orbital on the long-range coupling pathway. The C2H2→*C1=Y and C6H6→*C1=Y (Y = O e S) hyperconjugative interactions for the equatorial conformer indeed contribute for the 4JH2,H6 transmission mechanism. Surprisingly, the 4JH2,H6 value is higher for the carbonyl compounds, although the interactions C2H2→*C=Y and C6H6→*C=Y are more efficient for the thiocarbonyl compounds. Accordingly, the Fermi Contact (FC) contribution for the thiocarbonyl compounds decays deeper than in ketones, thus reducing more the 4JH2,H6 values. Moreover, both C=S *C-X and C=S *C-H interactions seem to be stronger in thiocarbonyl than in carbonylic compounds. The implicit solvent effect (DMSO and water) on the coupling constant values was negligible when compared to the gas phase. On the other hand, an explicit solvent effect was found and 4JH2,H6 for the thiocarbonyl compounds appeared to be more sensitive than for the cyclohexanones.