The H nuclear quadrupole interaction parameters, 2 and , are closely related to the shape of the potential energy surface at hydrogen bonds and depend sensitively on their geometry. We measured the temperature dependence of the H NMR spectra of the crystalline acidic salts KDCO3, KD acetylenedicarboxylate, RbD acetylenedicarboxylate, and KD maleate, which contain very short O-D O type hydrogen ...

The debate over the possible role of strong, low-barrier hydrogen bonds in stabilizing reaction intermediates at enzyme active sites has taken place in the absence of an awareness of the upper limits to the strengths of low-barrier hydrogen bonds involving amino acid side chains. Hydrogen bonds exhibit their maximal strengths in isolation, i.e., in the gas phase. In this work, we measured the i...

A (1) (TS) J F,H(O) coupling pathway, dictated by a hydrogen bond, in some 2-fluorobenzoic acids has been observed, while such an interaction does not occur in 2-fluorophenol. Thus, this work reports the conformational analysis of 2-fluorophenylboronic acid (1), in order to evaluate a possible intramolecular OH∙∙∙F hydrogen bond in comparison to an nF→pB interaction, which mimics the quantum nF...

In the crystal structure of the title compound, C(10)H(6)N(2)O(6)·2H(2)O, the OH and NH groups each serve as a hydrogen-bond donor to one acceptor site whereas the water mol-ecules each serve as a hydrogen-bond donor to two acceptor sites. The hydrogen-bonding scheme gives rise to a three-dimensional network.

Low-barrier or short, strong hydrogen bonds have been proposed to contribute 10 to 20 kilocalories per mole to transition-state stabilization in enzymatic catalysis. The proposal invokes a large increase in hydrogen bond energy when the pKa values of the donor and acceptor (where Ka is the acid constant) become matched in the transition state (delta pKa=0). This hypothesis was tested by investi...

Molecules of 2-nitrobenzaldehyde hydrazone, C7H7N3O2, where Z' = 2, are linked by two N-H...N hydrogen bonds into isolated dimers, whereas in the isomeric 3-nitrobenzaldehyde hydrazone, where Z' = 1, the molecules are linked by one N-H...O hydrogen bond and one N-H...N hydrogen bond into a three-dimensional framework structure.

In the crystal structure of the title Schiff-base, C(20)H(21)N(3)O(4), the amino group forms an N-H⋯O hydrogen bond to the acetyl group of an adjacent mol-ecule, forming a zigzag chain. The 2-hydr-oxy group is inter-nally hydrogen bonded to the amido group though an O-H⋯O hydrogen bond.

The title compound, C(13)H(16)N(2)O(2)S, crystallizes in the thio-amide form with an intra-molecular hydrogen bond of type N-H⋯O(butyr-yl). Mol-ecules are linked into chains parallel to [10] by a further hydrogen bond of type N-H⋯O(acet-yl). C-H⋯O and C-H⋯S hydrogen bonds are also present.

Various ab initio calculations using the density-functional (DFT), the second order Möller-Plesset perturbation (MP2) and self-consistent reaction field (SCRF) theories were performed on thirteen theoretically possible inositol stereoisomers. Gas phase calculations reveal that the myo- and neo-isomers of inositol (bearing one and two axial hydroxyl groups, respectively) are marginally more stab...