Kinds Of Hydrogen Bonds Research Articles

A New Hydrogen Bond in Coal

The hydrogen bonds in four coals with different rank and different sulfur content were checked using the in situ diffuse reflectance FTIR (DRIFT) method. Besides the hydrogen bonds formed by −OH and −COOH groups, there exists a new kind of hydrogen bond (SH−N) formed by the −SH in the thiophenols or mercaptans and the nigrogen in pyridine-like compounds in coal. The absence of this shoulder peak in the IR spectra of low rank coals (even high sulfur) can be attributed to the high content of −COOH groups, and consequently the strong and broad absorbance in carboxylic acid dimers in this range covers the weak absorbance of SH−N. However, when the low rank coals were heated to 620 °C in Ar atmosphere and the −COOH disappears, the peak of SH−N clearly occurs. To summarize all the work on this new hydrogen bond, we assign it to the position of about 2514 cm-1.

Solvent effects on infrared spectra of 2-Methyl-4,5-dimethoxy-3-oxo-2H-pyridizine: Part 2. Binary solvent systems

This research on the solvent effects of 2-methyl-4,5-dimethoxy-3-oxo-2H-pyridizine (MDOP) in binary solvent systems on the infrared spectra for MDOP in n-hexane/CHCl3 mixture solvents showed that there were three forms of carbonyl stretching vibration band [ν(C=O)] of MPOP as the mole fraction of CHCl3 in the binary solvents changes. In pure n-hexane solvent, the ν(C=O) of MDOP appeared at a relatively high wavenumber. With CHCl3 added, the ν(C=O) shifted to lower wavenumbers. Two new bands were observed over a certain range of mixture solvent compositions. The origin of the bands was discussed in the terms of two kinds of hydrogen bond together with their individual dependence on mixture composition. Comparisons were drawn for the solvent sensitivities of ν(C=O) for propanone.

Competitive Hydrogen Bonds and Conformational Equilibria in Polysubstituted 3-Formyl-2-hydroxy-benzoyl Compounds

Stability sequences of rotational isomers were investigated for a series of polysubstituted 3-formyl-2-hydroxy-benzoyl compounds (acylresorcinols and acylphloroglucinols) at the B3LYP/6-31G(d,p) level of theory. Comparison with IR spectroscopically determined data revealed excellent agreement between theoretical prediction and experiment. The theoretical stability sequences were obtained by full geometry optimizations and, additionally, by an isodesmic reaction approach. In the latter case, the total interaction energy between the various substituents is determined from the sum of single interaction energies between each two adjacent substituents, which are calculated from corresponding interaction-forming reactions. It is shown that the isodesmic reaction approach provides a quick and easy, but nevertheless reliable means for estimating relative stabilization energies from a simple increment system. It also provides a valuable tool for a discussion of the importance of the single contributions. Expectedly, the number and kind of hydrogen bonds is clearly the first and most decisive factor that governs the conformational stabilities.

Theoretical study on the structure and stability of the clusters of tropylium ion solvated by methanol molecules

Density functional theory (DFT) B3LYP calculations characterize the structure and stability of the clusters of tropylium ion (Tr +) coordinated by methanol molecules Tr +(MeOH) n with n=1–7. Methanol molecules are bound together through strong O–H⋯O type hydrogen bonds, resulting in a cyclic structure when n≥3, and the methanol cluster thus formed coordinates to Tr + through weak C–H⋯O type hydrogen bonds. Thus, the formation of the Tr +(MeOH) n clusters is mediated by two kinds of hydrogen bonds. Calculated distances of the O–H⋯O hydrogen bonds lie in the range 1.570–1.991 Å (1.712 Å in average) while those of the C–H⋯O hydrogen bonds lie in the range 2.083–2.319 Å (2.160 Å in average). Mass spectroscopic experiments demonstrated that Tr +(MeOH) 4 is a dominant, magic-numbered species and that Tr +(MeOH) 3 and Tr +(MeOH) 5 are minor [Chemical Communication, (2001) in press]. The experimental result is analyzed from the viewpoint of energetics. The specific size effect on the stability of Tr +(MeOH) n is a direct consequence of the stability of the (MeOH) n fragment itself.

Diaquabis(hexamethylenetetramine-N)bis(isothiocyanato)manganese(II) tetraaquabis(isothiocyanato)manganese(II) dihydrate

The crystal structure of the title compound, [Mn(NCS)2(hmt)2(H2O)2]·[Mn(NCS)2(H2O)4]·2H2O, where hmt is hexa­methyl­ene­tetr­amine (C6H12N4), shows that each Mn atom is in an octahedral coordination enviroment, and that the independent uncharged components [Mn(NCS)2(hmt)2(H2O)2], [Mn(NCS)2(H2O)4] and H2O are linked together by three kinds of hydrogen bonds (O—H⋯N, O—H⋯O and O—H⋯S) to form a three-dimensional supramolecular structure.

Racemic γ -2- cis -6-diphenyl- trans -3-ethylpiperidin-4-one oxime, a crystal structure with Z ′ = 8

The crystal structure of the title compound contains eight molecules per asymmetric crystal unit, each four of the two enantiomers (Pa, a = 19.7547(3) A, b = 17.2606(2) A, c = 20.8149(4) A, β = 114.2656(16)°, V = 6470.4(2) A3, Z = 16). The independent molecules have significantly different conformations, and local pseudosymmetries are obeyed only very roughly. The oxime groups form the typical hydrogen bonded cyclic dimers, whereas the amine donors are not satisfied by any kind of hydrogen bonds.

Raman spectroscopy of urea and urea-intercalated kaolinites at 77 K

The Raman spectra of urea and urea-intercalated kaolinites have been recorded at 77 K using a Renishaw Raman microprobe equipped with liquid nitrogen cooled microscope stage. The NH 2 stretching modes of urea were observed as four bands at 3250, 3321, 3355 and 3425 cm −1 at 77 K. These four bands are attributed to a change in conformation upon cooling to liquid nitrogen temperature. Upon intercalation of urea into both low and high defect kaolinites, only two bands were observed near 3390 and 3410 cm −1. This is explained by hydrogen bonding between the amine groups of urea and oxygen atoms of the siloxane layer of kaolinite with only one urea conformation. When the intercalated low defect kaolinite was cooled to 77 K, the bands near 3700 cm −1 attributed to the stretching modes of the inner surface hydroxyls disappeared and a new band was observed at 3615 cm −1. This is explained by the breaking of hydrogen bonds involving OH groups of the gibbsite-like layer and formation of new bonds to the CO group of the intercalated urea. Thus it is suggested that at low temperatures two kinds of hydrogen bonds are formed by urea molecules in urea-intercalated kaolinite.

Pyridinium dihydrogenmonothiophosphate

By reaction of pyridine di­thio­monometa­phospho­ryl fluoride with ethyl­di­phenyl­phosphine in the presence of traces of water, we isolated crystals of the title compound, (I). In the structure of this salt, two kinds of hydrogen bonds were detected. They link N—H (part of the cation), as well as one O—H group (part of the anion), to the phospho­ryl O atom of the anion. The donor–acceptor distances are 2.654 (1) and 2.568 (1) Å, respectively. The P—O and P—S bond lengths are 1.514 (2) and 1.967 (1) Å, respectively, which fall therefore in the range of a 1.5-fold bond.

Pyridinium dihydrogenmonothiophosphate.

By reaction of pyridine dithiomonometaphosphoryl fluoride with ethyldiphenylphosphine in the presence of traces of water, we isolated crystals of the title compound, (I). In the structure of this salt, two kinds of hydrogen bonds were detected. They link N-H (part of the cation), as well as one O-H group (part of the anion), to the phosphoryl O atom of the anion. The donor-acceptor distances are 2.654 (1) and 2.568 (1) A, respectively. The P-O and P-S bond lengths are 1.514 (2) and 1.967 (1) A, respectively, which fall therefore in the range of a 1.5-fold bond.

Crystal structure and vibrational spectra of bis(betaine) sulfamate

The crystal structure of bis(betaine) sulfamate (BBAS) has been determined by X-ray diffraction method at 250 and 100 K as monoclinic, space group P21/c, Z=4. The crystal comprises of monoprotonated betaine dimers and sulfamate anions NH2SO3−. Two kinds of hydrogen bonds are present in the crystal: strong, symmetric and linear O···H···O hydrogen bonds (R(O···O)=2.448(2)–2.442(2) A) and weak N–H···O hydrogen bonds (R(N···O)=2.983(2)–3.028(2) A). At low temperature (100 K) the BBAS structure is completely ordered. At 250 K 5% of sulfamate anions have their orientation changed through inversion of the NH2 groups. Infrared transmission (for both BBAS and the deuterated from, DBBAS), reflection and Raman spectra of the title compound have been recorded and discussed in relation to the X-ray crystal structure. Additionally, temperature dependence of the BBAS infrared spectra in the 12–300 K range was investigated on purpose to find a possible relation between structural and spectroscopic changes in the studied crystal.

FTIR study of hydration of dodecatungstosilicic acid

The dehydration of H4SiW12 O40·15.6 H2O was studied in situ in the IR chamber. On evacuation at room temperature the departure of most loosely bonded water characterized by bands at 3550 and 1616 cm−1 was observed. In the remaining hexahydrate the band at 3445 cm−1 was ascribed to the hydrogen bond between the Od oxygen atom of the Keggin unit and dioxonium H5O2+ ion, the presence of which is manifested by the 1710 and 1100 cm−1 vibrations. All these bands vanish in the case of anhydrous H4SiW12O40, in which the band at 3106 cm−1 ascribed to the hydrogen bond between neighbouring HPA anions Od−H+−Oc is still present. The dehydration of hexahydrate is accompanied by splitting of the W=Od band into 987 and 1010 cm−1 reflecting the change of the kind of hydrogen bond in which the Od oxygen atom is involved. Based on the above results it was concluded that protons forming oxonium ions in hydrated solid heteropoly acid are more strongly bonded than those in anhydrous one which are forming hydrogen bonds between neighbouring Keggin units.

A New Type of Hydrogen Bond

Hydrogen bonding is responsible for a wide array of chemical properties, from the melting point of water to the behavior of enzymes. In his Perspective, Crabtree discusses recent work in which entirely new kinds of hydrogen bonds have been discovered. Understanding and controlling these new types of bonding may enable researchers to harness a variety of important catalytic processes.

The Monoclinic Form of Acetaminophen at 150K

The crystal structure of the anti-inflammatory agent acetaminophen [N-(4-hydroxyphenyl)acetamide, C8H9NO2] has been refined using a Siemens SMART three-circle automatic diffractometer with a charge-coupled device (CCD) detector at 150 K. Monoclinic crystals of acetaminophen were grown from ethanol solution (m.p. 443–444 K). The crystal structure exhibits two kinds of hydrogen bonds [2.656 (2) A, OH donates to O=C; 2.914 (2) A, HO accepts from HN]. The molecules form a pleated sheet parallel to the (101) plane. The sheets are stacked along [010]. The molecules within a stack are held together by van der Waals interactions. Molecules from different sheets form `head-to-tail'-type dimers.

Raman Spectra of Pinacol Hexahydrate in the Region of OH Stretches at Room Temperature

The polarized Raman spectra of pinacol hexahydrate (PHH) and 5% deuterated PHH were observed at room temperature in the region of the O–H and the decoupled O–D stretches, respectively. The decoupled O–D stretches were assigned on the basis of there being four kinds of hydrogen bond. The polarized Raman spectra of PHH were analysed using 108 water and 18 pinacol molecules with disorder in the hydrogen positions which satisfy a periodic boundary condition. The observed Raman spectra were explained well using the initial set of force constants with the exception of the intermolecular interaction constants. The observed Raman spectrum of deuterated PHH in the polycrystalline state was also reproduced well. The wavenumber of the in-phase ν1 mode of PHH and the intermolecular interaction constant are noticeably larger than those for related compounds.

3-(p-Hydroxyphenyl)propionic Acid

The title compound, C 9 H 10 O 3 , has a fully extended propionic side chain in a trans configuration ; the plane of the side chain is almost perpendicular to the phenyl-ring plane. The molecules are held together by two kinds of hydrogen bonds between hydroxyl groups and between carboxyl groups.

Formation of mesophase by hydrogen bond directed self-assembly between barbituric acid and melamine derivatives

The 1:1 mesophase was formed through molecular self-assembly directed by hydrogen bonding between light active barbituric acid derivative, 5-[4-dodecyloxybenzylidene]-2, 4, 6,-(1H, 3H)-pyrimidinetrione (B) and melamine derivative, 4-amino-2, 6-didodecylamino-1, 3, 5-triazine (M). It was found through temperature-dependent IR spectra that there are three kinds of hydrogen bonds with different strength in this mesophase. When dispersed in chloroform, this mesophase shows a double helical structure.

Thermoreversible gelation of hydrated polymers

Phase diagrams of aqueous polymer solutions which gel on heating are theoretically derived and compared with experimental observation on cellulose derivatives in water. Such an inverted gelation, often observed in aqueous polymer solutions, interferes with phase separation at high temperatures. It is shown by lattice theoretical analysis that the competition between polymer–polymer direct hydrogen bonding and polymer–water hydrogen bonding leads to the coexistence of inverted gelation and phase separation at high temperatures. Systematic shift of the sol–gel transition line relative to the miscibility gap is observed by changing the strength of the two kinds of hydrogen bonds.

Investigation of interactions in polyether-polyurethanes and their mixtures with other polyurethanes by high resolution n.m.r.

The hydrogen bonds in polyether-polyurethanes based on 4,4′-diphenylmethane diisocyanate, N-methyldiethanolamine (MDEA) and poly(tetramethylene oxide) glycol (PTMG) and their zwitterionomers were investigated by high resolution 1H n.m.r. in deuterated dimethyl formamide. There are four NH peaks in each of the 1H n.m.r. spectra resulting from four kinds of hydrogen bonds. The NH groups in the hard segments may form hydrogen bonds with the CO groups of the hard segments, the N atoms of the MDEA portions, the SO groups of γ-propanesulfonates and the O atoms of PTMG. The relative amounts and chemical shifts of the NH peaks do not change with polyurethane concentration. Mixtures of polyether-polyurethanes with a polysiloxane-polyurea and a polyester-polyurethane were also studied by 1H n.m.r. There are no hydrogen-bonding interactions between the hard segments of the two different polyurethanes in these mixtures. The hard segments of the two different polyurethanes cannot be mixed at the molecular level. This is proven by nuclear Overhauser effect spectroscopy (NOESY) for a mixture of a polyether-polyurethane with a polysiloxane-polyurea. The NOESY spectrum indicates that the soft segments of the two different polyurethanes can be mixed at the molecular level. Most of the hard segments form microdomains in concentrated solution. Neither the solvent nor water can invade the microdomains rich in hard segments. Thus we can study hydrogen-bonding interactions in concentrated solution and deduce those interactions in the solid state.

Study of hydrogen bonds in polyester-polyurethanes by solution n.m.r.

High resolution 1H n.m.r. spectra are used to investigate the hydrogen bonds in polyester-polyurethanes based on 4,4′-diphenylmethane diisocyanate, N-methyldiethanolamine and poly(ethylene-propylene) adipate and their zwitterionomers. There are several NH peaks in the 1H n.m.r. spectra resulting from different kinds of hydrogen bonds. In concentrated dimethyl sulfoxide (DMSO) and dimethyl formamide (DMF) solutions, there are few hydrogen bonds between the polyurethanes and the solvent or water. The solvent effect can be ignored for hydrogen bonds. The relative amounts and the half-widths of each NH peak remain the same in the temperature range 23–82°C. The chemical shifts of the NH peaks move to lower frequency at higher temperature. The strong hydrogen bonds between groups of the hard segments make the hard segments align in a very orderly fashion. The percentage of NH groups forming hydrogen bonds with CO groups of the hard segment is large (> 45%). Neither the solvent nor H 2O can destroy the strong hydrogen bonds of the hard segment groups in concentrated solution. We deduce the conformation of the hard segments from two-dimensional nuclear Overhauser effect spectroscopy. There is no exchange between NH groups. The conformation of the polyester-polyurethanes in concentrated solution is similar to that in the solid state. Thus we can study the hydrogen-bonding interactions in concentrated solution and deduce those interactions in the solid state.

Evidence for two kinds of hydrogen bond in ice

DESPITE its simplicity at the molecular level, water is a complex and poorly understood liquid1. The reasons for this centre around the existence of a dynamic hydrogen-bonded network throughout the liquid. Attempts to describe the structure of liquid water have tended to invoke either continuum models such as the 'distortedbond' model2, which assumes that the hydrogen-bonded structure relaxes on a timescale similar to that in other liquids, and mixture models, such as the 'flickering-cluster' model3, which postulate the coexistence of two or more long-lived structures in the liquid. Here we analyse inelastic neutron-scattering spectra for the ice I solid phase of water, which provide evidence for the existence of two different kinds of hydrogen-bond, of different strengths, in the solid. A model in which strong and weak hydrogen-bonds in the ratio of about 2:1 are randomly distributed throughout the network is able to reproduce the neutron spectra. If we can assume that the same kind of bimodal hydrogen-bonding exists in the liquid state, our model may be able to explain several of the anomalous properties of liquid water, such as the large specific heat and the unusual behaviour of water in thin films and clusters.