Density functional theory studies of transannular1H?1HJ-coupling in half-cage alcohols and rigid 1,3- and 1,4-diols: conformational dependencies and implications for intramolecular hydrogen bond detection in carbohydrates

Abstract

Density functional theory (DFT) methods were used to investigate the conformational dependence of transannular H-H coupling constants in half-cage alcohols and cage diols. Finite perturbation theory (FPT) was used to obtain the Fermi contact (FC) contributions to scalar coupling constants in three halfcage alcohols and the OH· · ·OH coupling between hydroxyl groups sharing 1,4-and 1,3-intramolecular hydrogen bonds. Transannular CH· · ·OH coupling constants in the half-cage alcohols (inner OH) were obtained as a function of the dihedral angle defining the OH orientation. In comparison with the parent compound, chlorine substituents substantially modify the conformational dependence of the transannular H-H coupling and lead to observable coupling in the hexachloro compound. This is an unusual case, wherein the conformationally averaged coupling constants are quite different than those for the minimumenergy conformations. A −1.0 Hz scalar coupling is predicted between the very crowded protons in the half-cage acetate (outer OAc) in comparison with the experimental magnitude <1 Hz. In model 1,4-and 1,3-diols the coupling constants were obtained as functions of the analogous dihedral angles. The primary effects of hydrogen bonding are the stabilization of conformations in which the positive and negative contributions effectively cancel, thereby leading to small, observed values (e.g. ≤0.3 Hz). The DFT/FPT data for transannular coupling constants are consistent with a sum-over-states analysis for the direct mechanisms involving the two bonds containing the coupled nuclei rather than indirect mechanisms associated with oxygen lone pairs. Discussed here are the prospects of using OH· · ·OH scalar coupling for structural studies of carbohydrates.

Review on DFT and ab initio Calculations of Scalar Coupling Constants

“…In cases were the proton is shared between A and B the distinction between 1 J AH and 1h J B···H disappears; finally, when the proton is completely transferred, the situation again becomes "classical", with The contribution of the Bartlett, Perera and Del Bene's group to this topic is so significant that we have decided to divide this section in three parts: a) Other groups [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]; b) Bartlett-Perera-Del Bene [25][26][27][28][29][30][31][32][33][34][35][36]; c) Data analysis [37][38][39][40][41].…”

“…Barfield's contribution is important having published four papers between 1999 and 2002 [14][15][16][17][18].…”

“…In these systems, two trans-hydrogen bond Table 7, Appendix) 2h J HH couplings in 1,3 and 1,4-diols of favorable conformation and computed (DFT/FTP) these couplings for different geometries of the fragment O-H···O-H with acceptable results [16,17]. In his last publication, Barfield addressed the problem of proteins, and specifically, the notorious 3h J NC' coupling [18].…”

Research involving NMR spectroscopy at undergraduate institutions in the United States

“…NMR isotopic perturbation methodology is correlated with the intramolecular hydrogen-bond geometry in architecturally well-designed compounds. They have discovered that hydrogen-bonded mediated scalar couplings can be used to detect spatial proximity of hydroxy groups [26,27,28,29].…”

Electronic Mechanisms of Intra and Intermolecular J Couplings in Systems with C-H···O Interactions

“…Great effort has been devoted to this subject in recent years [1][2][3][4][5][6][7][8][9][10]. In particular, it has been recognized that C-H...X interactions depend strongly on the kind of molecular moiety to which the C-H bond and X atom belong to [11,12].…”