Hydrogen Bonding (hydrogen + bonding)

Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Hydrogen Bonding

  • extensive hydrogen bonding
  • intermolecular hydrogen bonding
  • intramolecular hydrogen bonding
  • strong hydrogen bonding

  • Terms modified by Hydrogen Bonding

  • hydrogen bonding energy
  • hydrogen bonding interaction
  • hydrogen bonding network
  • hydrogen bonding pattern
  • hydrogen bonding strength

  • Selected Abstracts

    New Approaches to 12-Coordination: Structural Consequences of Steric Stress, Lanthanoid Contraction and Hydrogen Bonding

    Anthony S. R. Chesman
    Abstract The anionic dinitrile ligand dicyanonitrosomethanide (dcnm), C(CN)2(NO),, and the anion resulting from its addition product with water, carbamoylcyanonitrosomethanide (ccnm), C(CN)(CONH2)(NO),, have been incorporated into lanthanoid complexes and display unusual ,2(N,O) nitroso coordination modes. (Et4N)3[Ln(ccnm)6] (1Ln; 1Ln = 1La, 1Ce, 1Pr, 1Nd, 1Sm) and (Me4N)3[Ln(ccnm)6] (2Ln; 2Ln = 2La, 2Ce, 2Pr, 2Nd) are systems containing 12-coordinate homoleptic trianionic lanthanoidate complexes. The nitroso groups of the ccnm ligands form three-membered ring chelates with the lanthanoid metal centre, with the asymmetry of the nitroso ,2 interactions dependent upon the intramolecular N,H···O=N hydrogen bonding. Additional intermolecular hydrogen bonding interactions exist between adjacent amide and nitrile groups giving rise to 3D ,-Po and 6,8-connected (412.63)(420.68) networks in 1Ln and 2Ln, respectively. The compounds (Me4N)3[Ln(dcnm)6] (3Ln; 3Ln = 3La, 3Ce, 3Nd, 3Sm) also contain a 12-coordinate trianionic lanthanoidate complex with the nitroso group exhibiting a highly symmetrical ,2 interaction. The sterically crowded environments of [Ln(18-crown-6)(dcnm)3] (4Ln; 4Ln = 4La, 4Ce, 4Pr, 4Nd) result in a shift towards a more asymmetric ,2 bonding of the nitroso group with decrease in the Ln3+ radius. There is a corresponding increase of the Ln,O,N angle, and one ligand is ,1(O) binding in 4Nd. The dcnm ligands in the discrete complexes [La(phen)3(dcnm)(3,x)Clx], x , 0.25 (5) (phen = 1,10-phenanthroline), (Et4N)[Ce(phen)2(dcnm)4] (6a/b, 6c) and [Ce(phen)2(dcnm)Cl2H2O] (7) display a variety of coordination modes. Complex 5 has 1D chains formed by ,,, stacking of adjacent phen co-ligands. Complexes 6 contain the monoanionic complex [Ce(phen)2(dcnm)4], with two geometric isomers present in the crystal structure of 6a/b. Complex 7 forms extended 1D chains via hydrogen bonding between coordinated water and chloride atoms and an extensive array of face-to-face , interactions. [source]

    Aluminium Complexes of a Phenoxyimine Ligand with a Pendant Imidazolium Moiety: Synthesis, Characterisation and Evidence for Hydrogen Bonding in Solution

    Stefano Milione
    Abstract Novel alkylaluminium complexes (phim)AlMe2 (1) and(phimid)AlR2+Br, [R = Me (2), R = iBu (3)] bearing the Schiff base ligands 3,5- tBu2 -2-(OH)C6H2CH=NiPr (phim -H) and3,5- tBu2 -2-(OH)C6H2CH=NCH2CH2[CH(NCHCHNiPr)]Br(phimid -H·Br) have been prepared and fully characterised. Complexes 1,3 each have a tetrahedral structure, with the aluminium atom surrounded by the oxygen and nitrogen atoms of the chelating ligand and two alkyl groups. The structures of phimid -H·Br and of complex 1 have been determined by X-ray diffraction studies. Investigation of the solution structures of 1,3 by 1H NMR spectroscopy revealed that the coordinated phimid ligand is involved in hydrogen bonding with bromide anion. Treatment of 1 with B(C6F5)3 led smoothly to (phim)Al(C6F5)Me (4) by transfer of a C6F5 group from MeB(C6F5)3, to the initially formed coordinatively unsaturated cationic intermediate. In contrast, treatment of 2 with one equiv. of B(C6F5)3 afforded the cationic monomethyl species (phimid)AlMeBr+,MeB(C6F5)3, (5), stabilised by the coordination of the bromide anion acting as a Lewis base.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Variability in the Structures of Luminescent [2-(Aminomethyl)pyridine]silver(I) Complexes: Effect of Ligand Ratio, Anion, Hydrogen Bonding, and ,-Stacking

    Rodney P. Feazell
    Abstract The reaction of 2-(aminomethyl)pyridine (2-amp) with silver(I) salts of triflate (OTf,), trifluoroacetate (tfa,), and tetrafluoroborate (BF4,) produce monomeric, dimeric, bridged, and polymeric structural motifs. The structural characteristics are dependent upon the ratio of ligand/metal in the structure as well as the ability of the anion to coordinate to the metal centers and form hydrogen bonds to the bound ligands. The silver coordination environment takes on several geometries including near linear (6), trigonal (4), tetrahedral (1), and both trigonal-bipyramidal and square-based pyramidal in a single structure (2). Structures 2, 3, and 5 also display short Ag,Ag contacts ranging from 2.8958(3) to 3.0305(4) Å. The species with metal,metal interactions, which are connectively very similar to their metal-isolated counterparts of 1, 4, and 6, are held together only by weak ,-stacking interactions or hydrogen bonds to their respective anions. Low-temperature luminescence spectra were collected for all compounds and are compared. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

    Enol Forms of 1,3-Indanedione, Their Stabilization by Strong Hydrogen Bonding, and Zwitterion-Assisted Interconversion

    Mark Sigalov
    Abstract By analyzing NMR spectroscopic data, and supported by IR, UV/Vis, Raman, dielectrometry, and DFT techniques, a comprehensive study of the 1:2 adducts of picolinaldehyde and 1,3-indanediones is presented. The parent indanedione derivative 5 exists in an equilibrium between all-keto and enol forms, the latter being stabilized by an intramolecularO,H···N hydrogen bond. Only the all-keto form was observed in the 5,6-dimethoxy compound 6, whereas solely the enol tautomer was observed with its 5,6-dichloro analogue 7. Polar solvents and low temperatures shift the equilibrium towards the enol tautomer in 5. The structure of adduct 8, formed with isonicotinaldehyde, prevents the formation of intramolecular O,H···N hydrogen bonds and thus it exists in the all-keto form in low polar solvents. However, in DMSO solutions it adopts a zwitterionic form with a strong anionic O,···H···O hydrogen bond. Thus, the enol form in indanedione adducts was unequivocally characterized in solution and the factors that determine the keto,enol tautomerism, namely electronic effects, solvent, temperature, and intramolecular hydrogen bonds, have been methodically studied by spectroscopic and quantum mechanical methods. [source]

    Deslipping of Ester Rotaxanes: A Cooperative Interplay of Hydrogen Bonding with Rotational Barriers

    Petra Linnartz
    Abstract A series of rotaxanes has been synthesized which contain two ester groups in their axles. All rotaxanes bear the same tetralactam wheel. The kinetics of the de-slipping reaction of these rotaxanes were monitored in tetrachloroethane (TCE) and dimethyl sulfoxide (DMSO) resulting in the observation of a significant solvent effect. In TCE, two isomeric rotaxanes that differ merely with respect to the orientation of the ester groups show a remarkable difference in their deslipping behavior. When the ester carbonyl group is directly attached to the axle center piece, the rotaxane decomposes with a half life of ca. 10 h at 100 °C. The reverse orientation with the carbonyl group attached to the stopper blocks deslipping almost completely and a lower limit for the half life at 100 °C of 25,000 h was obtained. These results can be interpreted by inferring a cooperative action of hydrogen bonding between wheel and axle and differences in rotational barriers. Molecular modeling and AM1 calculations support this interpretation. The implications of these results for the determination of steric size and the optimization of molecular machines are discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

    Hydrogen Bonding of Fluorinated Saccharides in Solution: F Acting as H-Bond Acceptor in a Bifurcated H-Bond of 4-Fluorinated Levoglucosans,

    Bruno Bernet
    Abstract 4-Fluorinated levoglucosans were synthesised to test if OH,,,F H-bonds are feasible even when the O,,,F distance is increased. The fluorinated 1,6-anhydro- , - D -glucopyranoses were synthesised from 1,6,:,3,4-dianhydro- , - D -galactopyranose (8). Treatment of 8 with KHF2 and KF gave 43% of 4-deoxy-4-fluorolevoglucosan (9), which was transformed into the 3- O -protected derivatives 13 by silylation and 15 by silylation, acetylation, and desilylation. 4-Deoxy-4-methyllevoglucosan (19) and 4-deoxylevoglucosan (21) were prepared as reference compounds that can only form a bivalent H-bond from HOC(2) to OC(5). They were synthesised from the iPr3Si-protected derivative of 8. Intramolecular bifurcated H-bonds from HOC(2) to FC(4) and OC(5) of the 4-fluorinated levoglucosans in CDCl3 solution are evidenced by the 1H-NMR scalar couplings h1J(F,OH) and 3J(H,OH). The OH,,,F H-bond over an O,,,F distance of ca. 3.0,Å is thus formed in apolar solvents, at least when favoured by the simultaneous formation of an OH,,,O H-bond. [source]

    Supramolecular Organization of ssDNA-Templated ,-Conjugated Oligomers via Hydrogen Bonding

    ADVANCED MATERIALS, Issue 10-11 2009
    Mathieu Surin
    The templated self-assembly of water-soluble ,-conjugated molecules bearing a diaminotriazine moiety H-bonding to a single-strand oligothymine template leads to defined structures. We study these assemblies with molecular modeling, circular dichroism spectroscopy, and scanning probe microscopy, to get a better understanding of the factors governing the supramolecular organization and structural order. [source]

    Cover Picture: Bidentate Ligands by Self-Assembly through Hydrogen Bonding: A General Room Temperature/Ambient Pressure Regioselective Hydroformylation of Terminal Alkenes (Adv. Synth.

    Abstract The cover picture shows a typical industrial reaction, hydroformylation of terminal alkenes, made possible in a test tube with ambient pressure and room temperature with high regioselectivities. For more details, see the Communication by Wolfgang Seiche, Alexander Schuschkowski, and Bernhard Breit on pages 1488,1494. [source]

    The Influence of Hydrogen Bonding on the Propagation Rate Coefficient in Free-Radical Polymerizations of Hydroxypropyl Methacrylate

    Sabine Beuermann
    Abstract The propagation rate coefficient kp was determined for hydroxypropyl methacrylate by applying pulsed laser initiated polymerizations and subsequent analysis of the polymer by size-exclusion chromatography. kp data were derived for polymerizations in bulk and in several solvents: toluene, tetrahydrofuran (THF), benzyl alcohol, and supercritical CO2. With the exception of THF, no solvent influence on kp was observed. For polymerizations in THF kp values 40% below the corresponding bulk data were obtained. In addition, the activation energy of kp for polymerizations in THF is higher than for the other systems. The results are explained by a complexation of the OH group contained in the ester group with THF. As a consequence, H bonds between OH groups and carbonyl O atoms, which occur in the other systems, are not formed in the presence of THF. This explanation is supported by Raman spectra, which show that association of carbonyl groups does not occur for systems containing THF, whereas for all other systems the occurrence of two peaks at 1,703 cm,1 and 1 720 cm,1 is indicative of the vibrations of two different , associated vs. not associated , types of carbonyl groups. Based on the change in activation energy it is suggested that a true kinetic solvent effect occurs. Temperature dependence of kp for HPMA polymerizations in bulk and in solution of THF. The literature data for bulk polymerizations are taken from ref. 22. Open symbols refer to ,rep,=,10 Hz and filled symbols to ,rep,=,25 Hz. [source]

    Topological properties of hydrogen bonds and covalent bonds from charge densities obtained by the maximum entropy method (MEM)

    Jeanette Netzel
    Charge densities have been determined by the Maximum Entropy Method (MEM) from the high-resolution, low-temperature (T, 20,K) X-ray diffraction data of six different crystals of amino acids and peptides. A comparison of dynamic deformation densities of the MEM with static and dynamic deformation densities of multipole models shows that the MEM may lead to a better description of the electron density in hydrogen bonds in cases where the multipole model has been restricted to isotropic displacement parameters and low-order multipoles (lmax = 1) for the H atoms. Topological properties at bond critical points (BCPs) are found to depend systematically on the bond length, but with different functions for covalent C,C, C,N and C,O bonds, and for hydrogen bonds together with covalent C,H and N,H bonds. Similar dependencies are known for AIM properties derived from static multipole densities. The ratio of potential and kinetic energy densities |V(BCP)|/G(BCP) is successfully used for a classification of hydrogen bonds according to their distance d(H...O) between the H atom and the acceptor atom. The classification based on MEM densities coincides with the usual classification of hydrogen bonds as strong, intermediate and weak [Jeffrey (1997). An Introduction to Hydrogen Bonding. Oxford University Press]. MEM and procrystal densities lead to similar values of the densities at the BCPs of hydrogen bonds, but differences are shown to prevail, such that it is found that only the true charge density, represented by MEM densities, the multipole model or some other method can lead to the correct characterization of chemical bonding. Our results do not confirm suggestions in the literature that the promolecule density might be sufficient for a characterization of hydrogen bonds. [source]

    Dispersion-Driven Hydrogen Bonding: Predicted Hydrogen Bond between Water and Platinum(II) Identified by Neutron Diffraction,

    ANGEWANDTE CHEMIE, Issue 41 2010
    Dr. Silvia Rizzato
    Klassisch oder nicht? Die Metallionen quadratisch-planar koordinierter d8 -Komplexe können als Lewis-Säuren oder -Basen mit H2O-Molekülen in axialen Positionen wechselwirken. Ab-initio-Rechnungen zufolge bilden neutrale PtII -Komplexe Wasserstoffbrücken mit H2O, in denen PtII als Lewis-Base auftritt. Solche nichtklassischen OH,,,Pt-Brücken wurden nun in Kristallen von trans -[PtCl2(NH3)(N -Glycin)],H2O mithilfe von Neutronenbeugung identifiziert. [source]

    Hydrogen Bonding Makes a Difference in the Rhodium-Catalyzed Enantioselective Hydrogenation Using Monodentate Phosphoramidites.

    CHEMINFORM, Issue 9 2007
    Yan Liu
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

    Thiourea-Catalyzed Asymmetric Michael Addition of Activated Methylene Compounds to ,,,-Unsaturated Imides: Dual Activation of Imide by Intra- and Intermolecular Hydrogen Bonding.

    CHEMINFORM, Issue 48 2006
    Tsubasa Inokuma
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

    ChemInform Abstract: A Supramolecular Array of Fullerenes by Quadruple Hydrogen Bonding.

    CHEMINFORM, Issue 29 2002
    Luis Sanchez
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    ChemInform Abstract: A Novel Nine-Membered Intramolecular Hydrogen Bonding in Methyl Naphthoate Bearing Phenol Moiety.

    CHEMINFORM, Issue 27 2001
    Yasuharu Yoshimi
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    ChemInform Abstract: Supramolecular Organization of Fullerenes by Quadruple Hydrogen Bonding.

    CHEMINFORM, Issue 18 2001
    Minze T. Rispens
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    ChemInform Abstract: A New Approach to Supramolecular C60 -Dimers Based in Quadruple Hydrogen Bonding.

    CHEMINFORM, Issue 18 2001
    Juan J. Gonzalez
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    ChemInform Abstract: Stereoselective Photocycloaddition of Alkenes to Naphthalene Rings Assisted by Hydrogen Bonding.

    CHEMINFORM, Issue 12 2001
    Akihiro Yokoyama
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    Guanidinium Alkynesulfonates with Single-Layer Stacking Motif: Interlayer Hydrogen Bonding Between Sulfonate Anions Changes the Orientation of the Organosulfonate R Group from "Alternate Side" to "Same Side"

    Karim Bouchmella
    Abstract Hydrolyses of HCCSO3SiMe3 (1) and CH3CCSO3SiMe3 (2) lead to the formation of acetylenic sulfonic acids HCCSO3H,2.33,H2O (3) and CH3CCSO3H,1.88,H2O (4). These acids were reacted with guanidinium carbonate to yield [+C(NH2)3][HCCSO3,] (5) and [+C(NH2)3][CH3CCSO3,] (6). Compounds 1,6 were characterized by spectroscopic methods, and the X-ray crystal structures of the guanidinium salts were determined. The X-ray results of 5 show that the guanidinium cations and organosulfonate anions associate into 1D ribbons through (8) dimer interactions, whereas association of these ions in 6 is achieved through (8) and (6) interactions. The ribbons in 5 associate into 2D sheets through (8) dimer interactions and (12) rings, whereas those in 6 are connected through (6) and (8) dimer interactions and (14) rings. Compound 6 exhibits a single-layer stacking motif similar to that found in guanidinium alkane- and arenesulfonates, that is, the alkynyl groups alternate orientation from one ribbon to the next. The stacking motif in 5 is also single-layer, but due to interlayer hydrogen bonding between sulfonate anions, the alkynyl groups of each sheet all point to the same side of the sheet. [source]

    Helix Formation in Synthetic Polymers by Hydrogen Bonding with Native Saccharides in Protic Media

    Minoru Waki
    Abstract Water-soluble poly(m -ethynylpyridine)s were designed to realize saccharide recognition in protic media. UV/Vis, 1H NMR, and fluorescence measurements revealed that the polymer forms a helical higher order structure by solvophobic interactions between the ethynylpyridine units in the protic medium. The resulting pore in the helix behaves like a binding pocket in proteins, by taking advantage of inwardly directed hydrogen-bonding functional groups of the polymers. Molecular recognition of native saccharides by the polymers was investigated by circular dichroism (CD). The chirality of the saccharide was transferred to the helical sense of the polymers, accompanied by the appearance of induced CDs (ICDs) in the absorptive region of the polymers. In MeOH/water (10/1), mannose and allose showed intense ICDs, and the apparent association constant between the polymer and D -mannose was 14,M,1. [source]

    On Differences between Hydrogen Bonding and Improper Blue-Shifting Hydrogen Bonding

    CHEMPHYSCHEM, Issue 4 2005
    Wiktor Zierkiewicz Dr.
    Abstract Twenty two hydrogen-bonded and improper blue-shifting hydrogen-bonded complexes were studied by means of the HF, MP2 and B3LYP methods using the 6-31G(d,p) and 6,311++G(d,p) basis sets. In contrast to the standard H bonding, the origin of the improper blue-shifting H bonding is still not fully understood. Contrary to a frequently presented idea, the electric field of the proton acceptor cannot solely explain the different behavior of the H-bonded and improper blue-shifting H-bonded complexes. Compression of the hydrogen bond due to different attractive forces,dispersion or electrostatics,makes an important contribution as well. The symmetry-adapted perturbation theory (SAPT) has been utilized to decompose the total interaction energy into physically meaningful contributions. In the red-shifting complexes, the induction energy is mostly larger than the dispersion energy while, in the case of blue-shifting complexes, the situation is opposite. Dispersion as an attractive force increases the blue shift in the blue-shifting complexes as it compresses the H bond and, therefore, it increases the Pauli repulsion. On the other hand, dispersion in the red-shifting complexes increases their red shift. [source]

    Hydrogen bonding of modified bases involving Watson-Crick sites: Crystal structure and conformation of Benzyl 6-aminopurine-7-carboxylate

    J. M. Ohrt
    Abstract Crystals of benzyl 6-aminopurine-7-carboxylate (C13H11N5O2) are monoclinic, space group C2/c, Z = 8, with a = 25.448 (9), b = 6.052 (1), c = 16.975 (6)Å, , = 112.05 (5)°, M = 269.27, Dm= 1.49, Dx= 1.48 g/cm3. The structure was determined from three-dimensional diffractometric data by the multisolution technique and refined to a final reliability factor of 0.068. The molecule is planar with an intramolecular hydrogen bond from one of the amino hydrogens, Ha(N6) to the keto oxygen O(10) of the acyl group. The molecules are hydrogen bonded across the center of inversion by a pair of intermolecular hydrogen bonds using the Watson-Crick sites. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Low Molecular Weight Gelators with Hexagonal Order in Their Liquid-Crystal Phases and Gel States: 5-Cyano-2-(3,4,5-trialkoxybenzoylamino)tropones,

    ADVANCED MATERIALS, Issue 10 2003
    M. Hashimoto
    5-Cyano-2-(3,4,5-trialkoxybenzoylamino)tropones form hexagonal structures in both liquid-crystalline and gel states. The Figure shows an environmental scanning electron microscopy image of octanol gels. Hydrogen bonding between the tropone carbonyl group and the NH group of troponoid amides plays an important role in flattening the molecules, allowing tighter packing structures and more stable columnar mesophases and gel states. [source]

    Complexes self-associate by hydrogen bonding and metallophilic attraction: Theoretical study

    Fernando Mendizabal
    Abstract Hydrogen bonding and metallophilic attractions are studied in the model systems: [(AuNH3Cl)2], [(AuNH(CH3)2Cl)2], [{Au2(,-SH)(PH2O)(PH2OH)}2], [(CuNH3Cl)2], and [{Cu(NH3)Cl}4] at the Hartree,Fock (HF) and second-order Møller,Plesset (MP2) levels. The two interactions are found to be comparable and prevailing in the final structure. It is determined that the aurophilic contact has a same magnitude that the hydrogen bonding, and is stronger than the cuprophilic interaction. The presence of hydrogen bond directs the growth of the crystal. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source]

    Dye,fiber interactions in PET fibers: Hydrogen bonding studied by IR-spectroscopy

    Karen De Clerck
    Abstract Dye,fiber interactions are studied in poly (ethylene terephthalate) fibers by FT-IR spectroscopy. It is shown for the first time that DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) serves as an easy applicable and accurate technique for the study of fibrous structures. This article focuses on the possible hydrogen bond interactions in the dye,fiber system, where the PET fibers are dyed with anthraquinone-based disperse dyes. The dyes and related anthraquinone structures are studied in both the dilute solution state, the solid state, and as present in the PET fibers. It is proven that 1-amino anthraquinones show strong "chelate-type" intramolecular hydrogen bonding in all three states. In the fibers an important supplementary intermolecular hydrogen bonding with the CO groups in the PET fiber is observed. The extend of hydrogen bonding seems to be prone to dye concentration variations. Further analysis by modulated differential scanning calorimetry links the hydrogen bonding to an intrinsic plasticizing effect of the dyes affecting the dye diffusion process. This thus offers a tool for the fundamental understanding of the dyeing process and possible observed differences in dyeing behavior in dye,fiber systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

    Lattice-fluid equation of state with hydrogen-bond cooperativity

    AICHE JOURNAL, Issue 2 2002
    Poongunran Muthukumaran
    Hydrogen bonding plays an important role in thermodynamic properties of polar fluids. Existing equations of state that include h-bonding cannot accurately predict the phase behavior for polar fluids. In the theories for h-bond-chain forming molecules, h-bonding strength is considered a constant at a given temperature and pressure. Infrared spectroscopy and ab initio calculations show that the h-bonding strength depends on whether or not the molecule was previously h-bonded at other sites. When an h-bond is formed between an already hydrogen-bonded species and a free species, the second h-bond has different energetic characteristics from the primary h-bond. In the case of l-alkanol self-h-bonding, the equilibrium constant for the second h-bond is ten times that for the primary h-bond. This phenomenon called h-bond cooperativity was incorporated in a lattice-fluid-hydrogen-bonding equation of state. Calculations for pure l-alkanols, show that the theory can be improved significantly by the incorporation of h-bond cooperativity. Agreement with the phase behavior and spectroscopic h-bonding data improves using cooperativity, without any additional adjustable parameters. Heat of mixing calculations agree well with the experimental data. [source]

    A nitrogen-15 NMR study of hydrogen bonding in 1-alkyl-4-imino-1,4-dihydro-3-quinolinecarboxylic acids and related compounds

    Laurence Carlton
    Abstract The title compounds contain groups (amine, amide, imine, carboxylic acid) that are capable of forming intramolecular hydrogen bonds involving a six-membered ring. In compounds where the two interacting functional groups are imine and carboxylic acid, the imine is protonated to give a zwitterion; where the two groups are imine and amide, the amide remains intact and forms a hydrogen bond to the imine nitrogen. The former is confirmed by the iminium 15N signal, which shows the coupling of 1J(15N,1H) ,85 to ,86.8 Hz and 3J(1H,1H) 3.7,4.2 Hz between the iminium proton and the methine proton of a cyclopropyl substituent on the iminium nitrogen. Hydrogen bonding of the amide is confirmed by its high 1H chemical shift and by coupling of the amide hydrogen to (amide) nitrogen [(1J(15N,1H) ,84.7 to ,90.7 Hz)] and to ortho carbons of a phenyl substituent. Data obtained from N,N -dimethylanthranilic acid show 15N1H coupling of (,)8.2 Hz at 223 K (increasing to (,)5.3 Hz at 243 K) consistent with the presence of a N··· HO hydrogen bond. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Extended Car,Parrinello molecular dynamics and electronic g -tensors study of benzosemiquinone radical anion,

    James R. Asher
    Abstract Car-Parrinello molecular dynamics simulations of benzoquinone and benzosemiquinone radical anion in both aqueous solution and the gas phase have been carried out at ambient conditions. Hydrogen bonding is considerably more extensive to the anionic than to the neutral aqueous system. In addition to the conventional hydrogen bonding to the carbonyl oxygen atoms, T-stacked hydrogen bonding to the , -system is statistically and energetically significant for the semiquinone anion but not for the neutral quinone. EPR g -tensors have been calculated at DFT level for snapshots taken at regular intervals from the gas-phase and solution semiquinone anion trajectories. Different criteria for extraction of semiquinone/water clusters from the solution trajectory give insight into the effects of different interactions on the g -tensor, as does correlation of the g -tensor with statistically significant hydrogen-bond configurations identified along the trajectories. Comparison of gas-phase and solution results indicates opposite directions of direct electronic and indirect structural influences of hydrogen bonding on g -tensors. Short-time oscillations in gx along the trajectory are due mainly to CO bond vibrations. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Gas-phase basicities of polyfunctional molecules.

    Part 1: Theory, methods
    Abstract The experimental and theoretical methods of determination of gas-phase basicities, proton affinities and protonation entropies are presented in a tutorial form. Particularities and limitations of these methods when applied to polyfunctional molecules are emphasized. Structural effects during the protonation process in the gas-phase and their consequences on the corresponding thermochemistry are reviewed and classified. The role of the nature of the basic site (protonation on non-bonded electron pairs or on ,-electron systems) and of substituent effects (electrostatic and resonance) are first examined. Then, linear correlations observed between gas-phase basicities and ionization energies or substituent constants are recalled. Hydrogen bonding plays a special part in proton transfer reactions and in the protonation characteristics of polyfunctional molecules. A survey of the main properties of intermolecular and intramolecular hydrogen bonding in both neutral and protonated species is proposed. Consequences on the protonation thermochemistry, particularly of polyfunctional molecules are discussed. Finally, chemical reactions which may potentially occur inside protonated clusters during the measurement of gas-phase basicities or inside a protonated polyfunctional molecule is examined. Examples of bond dissociations with hydride or alkyl migrations, proton transport catalysis, tautomerization, cyclization, ring opening and nucleophilic substitution are presented to illustrate the potentially complex chemistry that may accompany the protonation of polyfunctional molecules. © 2007 Wiley Periodicals, Inc., Mass Spec Rev 26:775,835, 2007 [source]

    Smart materials based on self-assembled hydrogen-bonded comb-shaped supramolecules

    THE CHEMICAL RECORD, Issue 4 2004
    Gerrit Ten Brinke
    Abstract Block copolymer self-assembly and supramolecular chemistry can be combined most naturally to prepare smart polymer nanomaterials. An attractive route is based on comb-shaped supramolecules, obtained by attaching side chains to (co)polymers by physical (non-covalent) interactions. Hydrogen bonding is a key element of our approach. It combines an ease of synthesis with other important approach-specific elements, such as hierarchical self-assembly, strongly enhanced processability, swelling, and cleaving. Functional properties discussed include anisotropic proton conductivity, switching proton conductivity, electronically conducting nanowires, polarized luminance, dielectric stacks (optical reflectivity), functional membranes, and nano objects. © 2004 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 4: 219,230; 2004: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20018 [source]