Asymmetric Hydrogen Bond Research Articles

Notes. Crystal structure of sodium dihydrogen triacetate

In the crystal structure of NaH2[O2CCH3]3 the residues CH3CO2H and CH3CO2– are crystallographically distinct; they are co-ordinated to the Na+ ions forming chains parallel to the c axis, which are strengthened by short asymmetric hydrogen bonds. Intermolecular interactions hold together these parallel chains. The crystals are tetragonal, space group P41, with a= 8.266(1), c= 14.794(2)A, Z= 4, and R= 0.050 for 609 ‘observed’ reflections

Solution and Solid State Studies on the Interactions of Protonated Cytosine Salts. IV. Asymmetric Interbase Hydrogen Bonding and Interpyrimidine Base Stacking in Triply Hydrogen-Bonded Cytosine Complexes. Crystal and Molecular Structure of Bis[1-Methylcytosine, 1-Methylcytosinium] Hexafluorosilicate Dihydrate

Abstract The crystal and molecular structures of the complex bis(1-methylcytosine, 1-methylcytosinium) hexafluorosilicate dihydrate are reported. In the solid, a 1:1 triply hydrogen-bonded complex consisting of one protonated and one neutral 1-methylcytosine base is observed. The hydrogen bonding in the complex cation is asymmetric, and the asymmetry in the interbase hydrogen bonding is stimulated to a large part by base stacking. The observed infinite, helical array of stacked complexes, in which the base stacking is strong [mean stacking distance = 3.36A] is such that the molecular overlap is between protonated and neutral 1-methylcytosine bases. The asymmetric interbase hydrogen bonding and the protonated/neutral base stacking mode coexist in a synergistic interrelationship which maximizes the molecular and crystal forces. The results found in this study are compared with a variety of other systems in which asymmetrically hydrogen-bonded cytosine complexes are observed, and it is found that although base stacking is also a predominant feature of these complexes in the solid, the base stacking found in this study is different.

Redetermination of the structure of 1,4-dihydroxyanthraquinone (C14H8O4)*

Abstract The crystal and molecular structure of 1,4-dihydroxyanthraquinone has been determined by X-ray diffraction techniques. The substance crystallizes in the space group P21/a with cell parameters a = 20.339(5)Å, b = 6.017(1)Å, c = 10.391(2)Å, β = 125.46(1)°, and four molecules per unit cell. The structure was solved by direct methods and refined by the full matrix least-squares technique to a final R-value of 0.041 (Rω = 0.036, ω = 1). The molecules form both asymmetric intramolecular and intermolecular hydrogen bonds. There are remarkably short intermolecular approach distances of 2.644 Å and 2.778 Å between neighboring oxygen atoms.

Spectroscopic study of hydrogen bonding in the enol form of β-diketones—II. Symmetry of the hydrogen bond

Abstract The effects of proton potential on the i.r. and Raman spectra of β-diketones are discussed. The spectroscopic behaviour of the asymmetric hydrogen bond stretching mode and of the out-of-plane hydrogen bond bending modes indicates a relatively high barrier double minimum potential. From the observed O…O distances and these predicted from the spectroscopic results for intermolecular H-bonds, a bent hydrogen bond was concluded. The spectroscopic data show a great change in the internal modes of β-diketones upon deuteration. This was attributed to the lengthening of the O…O distance which is a known characteristic of a double minimum potential.

An X-ray study of a very short, asymmetric hydrogen bond between a protonated molecule of 1,5-dimethyl-1,5-naphthyridine-4(1H),8(5H)-dione and a CF3COO− anion

An X-ray study of a very short, asymmetric hydrogen bond between a protonated molecule of 1,5-dimethyl-1,5-naphthyridine-4(1H),8(5H)-dione and a CF3COO− anion

Wide-line and high-resolution proton magnetic resonance in single crystals of malonic acid

Single crystals of malonic acid were investigated by Fourier transform “wide-line” and multiple-pulse “high-resolution” techniques. Crystal spheres were used to avoid warping of the applied field by bulk susceptibility shape effects. The analysis of the wide-line spectra revealed asymmetric hydrogen bonds in malonic acid and a twist of about 6° of the methylene proton internuclear vector with respect to the normal of the CCC backbone of the molecule. All four chemically shifted lines possible by crystal symmetry could be resolved in the high-resolution spectra. The analysis of these spectra yielded the nuclear magnetic shielding tensors of all the protons in malonic acid. Particular emphasis is laid on the methylene proton shielding tensors which had not been determined previously. They turned out not to be fully congruent within experimental accuracy. Their anisotropies, 4.85 ± 0.3 and 3.80 ± 0.3 ppm, respectively, and their asymmetry parameters η 0.4 and 0.8, respectively, are compared with the corresponding parameters of methylene proton shielding tensors in a variety of compounds of which powder spectra have been recorded. The shielding anisotropy of the methylene protons in malonic acid appears to be unusually small. The problem of assigning shielding tensors to proton sites is solved in a purely experimental manner by analyzing the widths of the resonance lines in multiple-pulse spectra.

Dynamics of the hydrogen bond: two-dimensional model and isotope effects

In the adiabatic approximation the AHB linear triatomic model of a hydrogen bond is suggested to have two degrees of freedom: x (an AH anharmonic stretching vibration of a reduced mass μ 1 - fast subsystem) and X (the A…B stretching vibration - slow subsystem). An asymmetric hydrogen bond of the type A-H…B) as well as a single-well symmetric one (A…H…A) are discussed. The coupling of the subsystems induces a change in the equilibrium interatomic distance R ) (A…B) by X 0. Allowance for the latter permits one to establish the relations between the frequency ν(AH), the equilibrium bond lengths r′ o(AH) and R o of asymmetric hydrogen bonds, and explaining some relevant experimental regularities. The μ 1 dependence of X 0 and that of a ν(AH) anharmonicity permits one to account for the isotope effects for R o, r′ o and ν for both asymmetric and symmetric hydrogen bonds. The relation between the isotopic frequency ratio, ν(AH)/ν(AD), and ν 0(AH)/ν(AH) for asymmetric bonds is derived and seems to be confirmed by all published experimental data.

Liaison hydrogène O-H-O symétrique: II. Spectres de vibration des oxalates acides de lithium hydratés et anhydres

Infrared and Raman spectra of polycrystalline LiHC 2O 4, LiHC 2O 4, · H 2O and their D and 6Li containing isotopic derivatives have been investigated at 300 and 90 K in the 4000–50 cm −1 region. All the internal and external optically active modes of lithium hydrogen oxalate monohydrate have been identified and an assignment is given. The spectroscopic data are consistent with X-ray data showing an asymmetric short hydrogen bond with a positive deuterium isotope effect. The dehydration of LiHC 2O 4, · H 2O changes the type of hydrogen bond which becomes symmetric of the double minimum type. The deuteration of LiHC 2O 4, on the other hand. weakens the hydrogen bond and makes it asymmetric again. The asymmetry appears more pronounced at low temperature.

Investigation of the hydrogen bonding in chlorocarboxylate anions using 35Cl quadrupole resonance spectroscopy

35 Cl quadrupole resonance frequencies have been measured in a wide range of normal and acid salts of chlorocarboxylic and chlorobenzoic acids. The multiplicity of 35Cl signals and the shifts of the 35Cl frequencies on deuteriation of the acid proton in salts containing the anion [RCO2‥ H ‥ CO2R]– have been used to establish the symmetry of the hydrogen bond. The observed deuteriation shifts can be as large as 0.9 % of the 35Cl frequency in asymmetric hydrogen bonds; they are negligibly small if the hydrogen bond is symmetric.

Dynamical Theory of Ferroelectrics with Asymmetrical Hydrogen Bonds. Application to Rochelle Salt‐Type Crystals

AbstractA dynamical theory of ferroelectric phase transitions in crystals with asymmetric hydrogen bonds and several proton sublattices is developed. Owing to the presence of the proton‐phonon interaction and the tunnelling of protons, the phase transitions are of displacive type and are induced by the soft phonon‐proton mode. The temperature dependences of the spontaneous polarization and the dielectric constants of Rochelle salt (RS) and deuterated Rochelle salt (DRS) are calculated. The parameters of the theory are determined semi‐empirically. Good agreement with the experiment is obtained. The expected dependences of the frequencies of the soft phonon‐proton mode and pseudosoft proton‐phonon modes on temperature in RS are calculated.

Asymmetric single-minimum hydrogen bond in the bifluoride ion. Neutron diffraction study of p-toluidinium bifluoride

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAsymmetric single-minimum hydrogen bond in the bifluoride ion. Neutron diffraction study of p-toluidinium bifluorideJack M. Williams and Lynn F. SchneemeyerCite this: J. Am. Chem. Soc. 1973, 95, 17, 5780–5781Publication Date (Print):August 1, 1973Publication History Published online1 May 2002Published inissue 1 August 1973https://doi.org/10.1021/ja00798a067RIGHTS & PERMISSIONSArticle Views103Altmetric-Citations45LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (288 KB) Get e-Alerts Get e-Alerts

Adsorption of Ethylenediamine (EDA) on Montmorillonite Saturated with Different Cations—II. Hydrogen- and Ethylenediammonium-Montmorillonite: Protonation and Hydrogen Bonding

AbstractThe form under which ethylenediamine (EDA) is adsorbed from aqueous solution by hydrogen- and ethylenediammonium-montmorillonite was studied as a function of the amount of amine present in the system.EDA added to the acid clay in quantities lower than or equal to the cation exchange capacity (C.E.C.) was exclusively adsorbed as ethylenediammonium (EDAH22+) ion. On further addition of diamine the pH of the suspension rose to alkaline values and the monoprotonated species (EDAH+) was the main charge balancing cation.Evaporating at room temperature “EDA-H-montmorillonite-H2O” or “EDA-EDAH2-mont- morillonite-H2O” systems containing 300 me EDA/100 g clay did not cause loss of nitrogen, but degassing under high vacuum (10−5 mm Hg) did. Nevertheless, excess EDA molecules with respect to the C.E.C. were retained on the clay surface, at the expense of water molecules, through strong asymmetrical hydrogen bonds between their NH2 groups and the NH3+ groups of EDAH+ ions. On heating up to 160°C under vacuum the nitrogen content decreased further, but still remained at a level significantly higher than the C.E.C. value, all NH3+ groups remaining involved in strong hydrogen bonding. It is suggested that a “condensation” process takes place, implying evolution of EDA molecules and giving rise to “polymeric” associations between protonated and unprotonated diamine.Washing the clay suspensions with distilled water did not completely remove excess EDA either, as a consequence of the equilibrium existing between the ionic species in solution (EDAH22+ and EDAH+) and on the clay surface. It seems that these species were preferentially adsorbed as “trimeric” associations in which two out of four NH3+ groups are hydrogen bonded to NH2 groups.After heating at 200°C, nitrogen retained on the clay surface was mainly in the form of NH4+ ions. Ammonium formation was enhanced by the presence of excess EDA and was considerably faster than in montmorillonite systems containing EDA coordinated to Cu2+ ions.

What can theory say about the existence and properties of anomalous water?

An important, but little practiced, function of theory is to provide working models that unify and summarize experimental findings during the time when basic understanding of a phenomenon is actually evolving. Such a model for anomalous water has been previously proposed by us [ Science, 167, 1443 (1970)]. This model attempted to explain the phenomenon as (H 2O) n with a new type of chemical bonding, and its ability to correlate existing data is brought up to date in this paper. However, three new results invalidate our original model: (a) high-accuracy ab initio calculations showing that symmetric hydrogen bonds are 5 kcal/H-bond higher in energy than the usual asymmetric hydrogen bonds, (b) calculations showing absence of a strong, long-range wall effect, (c) a molecular weight measurement by Derjaguin et al. indicating an average value of 180. Because our original model did so well in consistently correlating such a wide variety of experimental data, our present disproof of this model leads us to conclude that polywater does not exist. Experimental reports suggesting a collection of organic and/or inorganic impurities as the origin of the properties attributed to anomalous water are critically analyzed and found inconclusive. Three other related hypotheses are examined theoretically and also found inadequate. Another working model based on trace amounts of silicates plus inorganic and/or organic anions is proposed on theoretical grounds. A list of key experiments is offered to help elucidate the fundamental nature of the anomalous material and to test this model.

Molecular orbital studies of the hydrogen bond

Extended Hückel and CNDO/2 molecular orbital methods have been employed to examine a variety of intermolecular and intramolecular hydrogen bonds including the symmetric bonds in the bifluoride and maleate ions. These molecular orbital methods provide valuable information on the dissociation energies, charge densities, bond orders, and dipole moments. The CNDO/2 method gives realistic double minimum potentials for the proton in the asymmetric hydrogen bonds and a single minimum potential in the bifluoride and maleate ions.

Symmetric versus asymmetric hydrogen bonds in polymeric water

Abstract The stability of symmetric and asymmetric hydrogen bonds in condensed ring structures of polymeric H2O was compared in the CNDO/2 method. In a six-membered ring the asymmetric structure is much more stable, but in condensed ring systems the difference between the two becomes smaller.

Deuteron Magnetic Resonance Study of Cupric Sulfate Pentahydrate

A deuteron magnetic resonance study is made of single crystals of CuSO4·5D2O between 130° and 360°K. The electric quadrupole coupling constant, the asymmetry parameter, and the directions of the principal axes of the field-gradient tensor are determined for each deuteron at 133.2° and 294.8°K. At low temperatures ten pairs of lines are observed, corresponding to five nonequivalent stationary water molecules. At temperatures above room temperature, five pairs of lines are observed; these are shown to result from fast molecular reorientation about the bisecting axis of each water molecule. An activation energy for the 180° reorientational motion is derived for each water molecule and is discussed in relation to the lonepair coordination of the oxygen atom of the water molecule and the hydrogen-bond strength. The field-gradient tensor for each stationary water molecule is discussed in relation to the structure of the hydrogen-bond system. For relatively weak asymmetric hydrogen bonds of O–H···O, an empirical equation, eQq/h = 310.0 − 3.0 × 190.6 / R(O···H)3 (kHz), is found to represent the observed values well, where R(O···H) is the O···H distance in angstrom units. For strong hydrogen bonds, there is a significant deviation from the above relation, indicating that the covalent effect is of importance in these cases. Coordination to a paramagnetic ion has no marked effect on the quadrupole coupling constant, but it appears to cause a rotation of the directions of principal x and y axes about the O–H bond. Two possible cases of the principal y-axes directions for the field-gradient tensor of the reorienting water molecule are analyzed in detail, and the available experimental data are classified into two groups. Theoretical formulas for the DMR spectra in the paramagnetic crystals are derived and compared with that in diamagnetic crystals. A local field due to the cupric ions is derived from the observed paramagnetic shift at 133.2°K for each deuteron and is found to be due to the electron nuclear spin dipole coupling. The spectra are observed at temperatures up to the dehydration point, and it is found that the free rotation of the water molecule does not occur in this temperature range.

Neutron and Infrared Spectra of HCrO2 and DCrO2

The vibrational spectra of HCrO2 and DCrO2 have been investigated by the energy-gain scattering of cold neutrons, and by infrared absorption spectra from 4000–30 cm−1. The infrared measurements are in agreement with previous results above 300 cm−1. In addition, no absorptions are observed between 300 and 30 cm−1, a region not covered in previous measurements. These results appear to support previous evidence for asymmetric hydrogen bonds in DCrO2 and essentially symmetric bonds in HCrO2. The neutron spectra exhibit a number of maxima, including a band peaked at about 225 cm−1 in HCrO2 (and a less intense peak around 180 cm−1 in DCrO2), probably due to low-frequency optic lattice modes. A comparison of the neutron and infrared results appears to raise some uncertainty concerning the assumption of symmetric hydrogen bonds in HCrO2.