Hydrogen bond

About: Hydrogen bond is a research topic. Over the lifetime, 57701 publications have been published within this topic receiving 1306326 citations.

Crystal field effects on the topological properties of the electron density in molecular crystals: The case of urea

Abstract: The Quantum Theory of Atoms in Molecules, due to Bader, is applied to periodic systems. Results for molecular and crystalline urea are presented. Changes in both bond critical points and atomic properties due to changes of chemical environment are described. A rationale for the different lengths of the in‐plane and out‐of‐plane hydrogen bonds and for the lengthening of the CO bond in bulk urea is provided in terms of the properties of the Laplacian of the oxygen atom electron density distribution. An evaluation of molecular and atomic volume changes indicates that the decrease of molecular volume upon change of phase from gas to solid originates primarily from a contraction of the atomic basins directly involved in hydrogen bonds. Other atoms show a small expansion. The considerable decrease of oxygen and hydrogen atomic volumes is related to the mutual penetration of their van der Waals envelopes following hydrogen bond formation. The results confirm that urea is more polar in the solid phase.

Hydrogen Bond Networks in Graphene Oxide Composite Paper: Structure and Mechanical Properties

Abstract: A multilayered composite structure formed by a random stacking of graphene oxide (GO) platelets is an attractive candidate for novel applications in nanoelectromechanical systems and paper-like composites. We employ molecular dynamics simulations with reactive force fields to elucidate the structural and mechanical properties of GO paper-like materials. We find that the large-scale properties of these composites are controlled by hydrogen bond networks that involve functional groups on individual GO platelets and water molecules within the interlayer cavities. Water content controls both the extent and collective strength of these interlayer hydrogen bond networks, thereby affecting the interlayer spacing and elastic moduli of the composite. Additionally, the chemical composition of the individual GO platelets also plays a critical role in establishing the mechanical properties of the composite—a higher density of functional groups leads to increased hydrogen bonding and a corresponding increase in stiffn...

Strong dimerization of ureidopyrimidones via quadruple hydrogen bonding

Abstract: 6-Methyl-2-butylureidopyrimidone dimerizes via four hydrogen bonds in the solid state as well as in CHCl3 solution via a donor−donor−acceptor−acceptor (DDAA) array of hydrogen bonding sites in the 4[1H]-pyrimidinone tautomer. An intramolecular hydrogen bond from the pyrimidine NH group to the urea oxygen atom preorganizes the molecules for dimerization. The dimerization constant of the dimer in CHCl3 exceeds 106 M-1. In CHCl3 containing DMSO, the dimer is in equilibrium with the monomeric 6[1H]-pyrimidinone tautomer. In 6-phenyl-2-butylureidopyrimidone, the 4[1H]-pyrimidinone tautomer coexists with the pyrimidin-4-ol form, which dimerizes with similar high dimerization constants via four hydrogen bonds in a DADA array. The latter tautomer predominates in derivatives with electronegative 6-substituents, like 6-nitrophenyl- and 6-trifluoromethyl-2-butylureidopyrimidone. Due to its simple preparation and high dimerization constant, the ureidopyrimidone functionality is a useful building block for supramolecu...

The Structure of Water Dimer from Molecular Beam Electric Resonance Spectroscopy.

Abstract: Molecular beams of hydrogen bonded water dimer, generated in a supersonic nozzle, have been studied using electric resonance spectroscopy. Radiofrequency and microwave transitions have been observed in (H2 16O)2, (D2 16O)2, and (H2 18O)2. Transitions arising from both pure rotation and rotation–tunneling occur. The pure rotational transitions have been fit to a rigid rotor model to obtain structural information. Information on the relative orientation of the two monomer units is also contained in the electric dipole moment component along the A inertial axis μa, which is obtained from Stark effect measurements. The resultant structure is that of a ’’trans‐linear’’ complex with an oxygen–oxygen distance ROO of 2.98(1) A, the proton accepting water axis is 58(6) ° with respect to ROO, and the proton donating water axis at −51(6) ° with respect to ROO. This structure is consistent with a linear hydrogen bond and the proton acceptor tetrahedrally oriented to the hydrogen bond. The limits of uncertainty are wh...