The structure of pure tertiary butanol

The technique of second-order difference neutron scattering with hydrogen/deuterium isotopic substitution has been used to measure the intermolecular structural correlations in pure liquid tertiary butanol. The newly developed technique of empirical potential structure refinement has been used to perform a detailed structural analysis of the resulting partial distribution functions, providing a means by which a full set of interatomic partial distribution functions consistent with the experimental data can be extracted. A comparison with our experimental results is made for a Monte Carlo model produced using fixed potentials as in earlier simulations of this alcohol system, and for the model which results from our procedure. The results suggest that the extent of intermolecular hydrogen bonding, although significant, is less dominant than generally accepted.     

Thermal neutron diffraction study of liquid phosphor tribromide under isobaric condition at 295 K.

The intermolecular scattering function of liquid phosphorous tribromide is studied under isobaric condition at 295 K in a range of the scattering parameter, 5.0 < κ [nm⁻¹l < 60. A striking resemblance is found with results reported on liquid SbCl₃. The intermolecular scattering function is tabulated in this paper. The liquid structure of PBr₃ can not be described very well by the RISM, similar to SbCl₃.     

Laser Diagnostics of the Mesoscale Heterogeneity of Aqueous Solutions of Polar Organic Compounds

A mesoscale droplet phase, which is spontaneously formed in aqueous solutions of some polar organic compounds, has been experimentally investigated by methods of dynamic light scattering and laser phase microscopy. It is shown that tetrahydrofuran and tert-butanol aqueous solutions demonstrate a strong peak of light scattering intensity in the range of molecular concentrations of about 0.02 to 0.08, which corresponds to inhomogeneities with a characteristic size of about 100 nm. These liquid droplets are enriched with molecules of dissolved substance. A similar light scattering peak for aqueous solutions of glycerol and ethylene glycol is less pronounced. A theoretical model of the phase separation of binary solutions with twinkling (i.e., existing for a finite time) intermolecular hydrogen bonds is developed. The model predicts the existence of an additional low-concentration light scattering peak near the spinodal of the solution free of hydrogen bonds. A characterization of solutions according to the numerical values of twinkling hydrogen bond parameters is outlined.     

Hydrogen bonding in liquid water: An ab initio QM/MM MD simulation study

Pattern and dynamics of hydrogen bonds in liquid water were investigated by a quantum mechanical/molecular mechanical molecular dynamics (QM/MM MD) simulation at Hartree–Fock (HF) level of theory. A large subregion of the whole system comprising two complete coordination shells was treated quantum mechanically in order to include all polarization and charge transfer effects and to obtain accurate data about structure and dynamics of the intermolecular bonds. The results of this investigation are in agreement with recent experimental findings and suggest that in liquid water every molecule forms in average 2.8, but almost as a rule less than four intermolecular hydrogen bonds.     

Dynamics of supercooled confined water measured by deep inelastic neutron scattering

In this paper, we present the results of deep inelastic neutron scattering (DINS) measurements on supercooled water confined within the pores (average pore diameter ~ 20 Å) of a disordered hydrophilic silica matrix obtained through hydrolysis and polycondensation of the alkoxide precursor Tetra-Methyl-Ortho-Silicate via the sol-gel method. Experiments were performed at two temperatures (250 K and 210 K, i.e., before and after the putative liquid–liquid transition of supercooled confined water) on a “wet” sample with hydration h ~ 40% w/w, which is high enough to have water-filled pores but low enough to avoid water crystallization. A virtually “dry” sample at h ~ 7% was also investigated to measure the contribution of the silica matrix to the neutron scattering signal. As is well known, DINS measurements allow the determination of the mean kinetic energy and the momentum distribution of the hydrogen atoms in the system and therefore, allow researchers to probe the local structure of supercooled confined water. The main result obtained is that at 210 K the hydrogen mean kinetic energy is equal or even slightly higher than at 250 K. This is at odds with the predictions of a semiempirical harmonic model recently proposed to describe the temperature dependence of the kinetic energy of hydrogen in water. This is a new and very interesting result, which suggests that at 210 K, the water hydrogens experience a stiffer intermolecular potential than at 250 K. This is in agreement with the liquid–liquid transition hypothesis.     

The structure of liquid deuterium bromide by slow-neutron scattering

Neutron diffraction measurements at 0·7 Å are reported for coexisting liquid deuterium bromide at -40°C. The results show that the deuterium bromide molecule in the liquid is little distorted as compared with the free molecule. The presence of a peak in the intermolecular pair distribution function at 3·1 Å is thought to be evidence of the formation of weak, rather long, intermolecular hydrogen bonds. As expected, both these effects are much weaker than for deuterium chloride reported in an earlier paper [2] and liquid deuterium bromide is therefore a simpler polar liquid.     

Ultrasonic and IR study of intermolecular association through hydrogen bonding in ternary liquid mixtures

Complex formation in ternary liquid mixtures of dimethylsulfoxide (DMSO) with phenol and o-cresol in carbontetrachloride has been studied by measuring ultrasonic velocity at 2 MHz, in the concentration range of 0.019-0.162 (in mole fraction of DMSO) at varying temperatures of 20, 30 and 40 degrees C. Using measured values of ultrasonic velocity, other parameters such as adiabatic compressibility, intermolecular free length, molar sound velocity, molar compressibility, specific acoustic impedance and molar volume have been evaluated. These parameters have been utilized to study the solute-solute interactions in these systems. The ultrasonic velocity shows a maxima and adiabatic compressibility a corresponding minima as a function of concentration for these mixtures. The results indicate the occurrence of complex formation between unlike molecules through intermolecular hydrogen bonding between oxygen atom of DMSO molecule and hydrogen atom of phenol and o-cresol molecules. The excess values of adiabatic compressibility and intermolecular free length have also been evaluated. The variation of both these parameters with concentration also indicates the possibility of the complex formation in these systems. Further, to investigate the presence of O-HO bond complexes and the strength of molecular association with concentrations, the infrared spectra of both the systems, DMSO-phenol and DMSO-o-cresol, have been recorded for various concentrations at room temperature (20 degrees C). The results obtained using infrared spectroscopy for both the systems also support the occurrence of complex formation through intermolecular hydrogen bonding in these ternary liquid mixtures.     

Hydrazide‐based non‐symmetric liquid crystal dimers: synthesis and mesomorphic behavior

Hydrazide‐based non‐symmetric liquid crystal dimers were synthesized. The liquid crystalline properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and powder X‐ray diffraction (XRD). These non‐symmetric liquid crystal dimers are evidenced to display the monolayer smectic C phase. The effects of the lateral intermolecular hydrogen bonding as well as the length of the terminal alkyl chains and the spacers on the mesophase are discussed. Our studies reveal that intermolecular hydrogen bonding between the hydrazide groups and microsegregation effect is the driving force for the formation of the monolayer smectic C structure. Copyright © 2007 John Wiley & Sons, Ltd.     

苯乙烯基吡啶类液晶化合物的分子结构及相变过程的光谱研究

通过本乙烯基吡啶和不同脂肪羧酸间的氢键作用构成液晶的方法具有合成路线灵活、简便、易于变化的特点,本文通过变温红外光谱对做为质子受体的苯乙烯基吡啶粉液晶化合物的分子结构和相变过程中分子排列的变化进行了研究,结果表明在液晶分子中象羰基这样的偶极矩较大的极性基团,对分子所处的相态分子间的相互排列比较敏感。在红外光谱中羰基伸缩振动的变化可以看作是液晶分子相态转变的标志。     

Quantum effects in the structure of liquid benzene at room temperature

Structural differences between liquid light (protonated) benzene and heavy (deuterated) benzene at room temperature have been measured using high energy electromagnetic radiation scattering techniques. Intra- and intermolecular effects have been examined, and the main quantum contribution is shown to be intramolecular. This is in contrast to the quantum effects measured in liquid water at room temperature, which are primarily intermolecular.     

Anomalously soft dynamics of water in a nanotube: a revelation of nanoscale confinement

Quasi-one-dimensional water encapsulated inside single-walled carbon nanotubes, here referred to as nanotube water, was studied by neutron scattering. The results reveal an anomalously soft dynamics characterized by pliable hydrogen bonds, anharmonic intermolecular potentials, and large-amplitude motions in nanotube water. Molecular dynamics simulations consistently describe the observed phenomena and propose the structure of nanotube water, which comprises a square-ice sheet wrapped into a cylinder inside the carbon nanotube and interior molecules in a chainlike configuration.     

X-ray emission spectroscopy of hydrogen bonding and electronic structure of liquid water

We use x-ray emission spectroscopy to examine the influence of the intermolecular interaction on the local electronic structure of liquid water. By comparing x-ray emission spectra of the water molecule and liquid water, we find a strong involvement of the a(1)-symmetry valence-orbital in the hydrogen bonding. The local electronic structure of water molecules, where one hydrogen bond is broken at the hydrogen site, is separately determined. Our results provide an illustration of the important potential of x-ray emission spectroscopy for elucidating basic features of liquids.     

Molecular spin resonance in the geometrically frustrated magnet MgCr2O4 by inelastic neutron scattering

We measured two magnetic modes with finite and discrete energies in an antiferromagnetic ordered phase of a geometrically frustrated magnet MgCr2O4 by single-crystal inelastic neutron scattering, and clarified the spatial spin correlations of the two levels: one is an antiferromagnetic hexamer and the other is an antiferromagnetic heptamer. Since these correlation types are emblematic of quasielastic scattering with geometric frustration, our results indicate instantaneous suppression of lattice distortion in an ordered phase by spin-lattice coupling, probably also supported by orbital and charge. The common features in the two levels, intermolecular independence and discreteness of energy, suggest that the spin molecules are interpreted as quasiparticles (elementary excitations with energy quantum) of highly frustrated spins, in analogy with the Fermi liquid approximation.     

羧酸吡啶类分子间氢键对光致异构化及光化学稳定性影响的谱学研究

以丁二酸胆甾醇单酯(CSA)作为质子给体,以4-对烷氧基苯甲酰氧基-4′-苯乙烯基吡啶(NCn)作为质子受体,通过羧酸和吡啶之间的氢键作用形成氢键诱导液晶化合物(CSA·NCn)。 利用紫外光谱研究了含苯乙烯基吡啶基团的液晶化合物NCn及其与丁二酸胆甾醇单酯(CSA)的氢键复合物CSA·NCn在溶液中的光致变色及光化学反应。 结果表明,在乙醇溶液中紫外光照射下二者均发生顺反异构化,分子间氢键对顺反异构化反应没有太大的影响;NCn化合物在氯仿溶液中,紫外光照射下发生光化学反应,而CSA·NCn的氯仿溶液,紫外光照射下只发生顺反异构化,这一方面说明光化学反应发生在吡啶的氮端,同时也表明这类氢键液晶化合物中的氢键比较稳定,光照下不发生解离;在NCn和CSA·NCn的乙醇溶液中加入H₂SO₄,两者均发生质子化。 表明强酸可以破坏CSA·NCn化合物中的氢键,使含吡啶端基解离出来,同H+发生质子化。     

The structure of liquid methylamine and solutions of lithium in methylamine

The technique of hydrogen/deuterium isotopic substitution in neutron diffraction has been used to measure the intra- and intermolecular correlations in liquid methylamine, and 2 and 8 MPM (mole percent metal) lithium methylamine solutions. We find that pure methylamine forms only one strong hydrogen bond per molecule, with evidence for weaker orientations towards the methyl group. As one introduces lithium metal, the intramolecular structure of the solvent is unaltered. However, intermolecular hydrogen bonding is progressively disrupted as the concentration of (solvated) cations and excess electrons increases. Comparison of the total structure factors for 0, 2, 8 and 20 MPM lithium methylamine solutions shows that the greatest shift in the position of the principal peak occurs between 8 and 20 MPM. This can be correlated to the electron delocalization associated with the non-metal-metal transition.     

Neutron scattering from aerosols: intraparticle structure factor, guinier analysis of particle speed, and crossed beam kinematics

A theoretical formalism for neutron scattering from systems of particles is applied to liquid nanodroplet aerosols. A term arising from intraparticle, intermolecular correlations is identified. The kinematical theory of two body scattering is recast into a form convenient for interpreting the results of experiments with crossed beams of neutrons and aerosol particles. Based on a theoretical analysis of the scattered intensity in the Guinier region, a method for determining the particle velocity directly from the experimental data is outlined. The method is not restricted by assumptions about particle shape, composition, uniformity, or size distribution.     

Determination of the lattice vibrations of imidazole by neutron scattering

The external molecular vibrations of deuterated imidazole have been investigated at 12 K for wave vectors along the three principal directions of the Brillouin zone by neutron scattering and by Raman scattering at the zone center. A complete symmetry assignment is obtained. The dominant role of the N-H … N hydrogen bond within the intermolecular interactions is reflected in a relatively simple manner in the shape of the dispersion curves because of the chain-like arrangement of hydrogen bonds. The experiment yields directly a stretching force constant of 0.33 mdyn Å^?1 for this bond. This value is compatible with monopole-dipole and dipole-dipole interactions as major contributions to the attractive interactions of the hydrogen bond of this length (2.86 Å). Relatively strong static monopoles and dipoles are confirmed by a $\text{CNDO}\text{2}$ calculation and are consequently incorporated into the interaction model.     

Is the hydrophobic effect unique to water? The relation between solvation properties and network structure in water and modified water models

The properties of water as a solvent are related to the structure of its liquid phase which in turn depends on the intermolecular potential. In order to explore this relationship we investigate the properties of liquids formed by a number of modified water models. Changing the molecular geometry changes short-range molecular correlations and the network of hydrogen bonds. The solubility and anomalously low entropy of non-polar solutes is only slightly reduced. Reducing the hydrogen-bond strength increases the solubility and removes the low entropy of solution of uncharged spheres. We conclude that the hydrophobic effect depends on the existence of hydrogen bonds and other strong intermolecular interactions but not on the presence of a three-dimensional network.     

IR spectra of benzaldehyde and its derivatives in different aggregate states

We have measured the IR Fourier-transform spectra of biologically active benzaldehyde and its derivatives in the gas and liquid phases. For compounds of this class, the role played by C=O, OH, and CH groups in intra- and intermolecular has been analyzed. We have revealed spectral features that characterize the participation of C=O groups of unsubstituted benzaldehyde molecules in the occurrence of intermolecular hydrogen bonds C=O...H-C with the formation of molecular dimers of different types. For 2-hydroxybenzaldehyde molecules, spectral data have been obtained that are indicative of the occurrence of intramolecular hydrogen bonds of the C=O...H-C type in solutions. In 2-methoxybenzaldehyde molecules, no intramolecular hydrogen bonds have been observed.     

Thermal neutron diffraction study of liquid carbon disulphide from 165 K to 318 K.

The structure factor of liquid carbon disulphide along the coexistence curve is studied at seven temperatures in the range 165 to 318 K and in a range of the scattering parameter, 9.5<κ[nm^?1]<34. The structure of the liquid over the entire range of states can be described well by the RISM with σ_S=0.33 nm and σ_C=0.34 nm. These values are in agreement with those reported by the majority of other authors. The intermolecular scattering functions are tabulated in this paper.