Interaction Of H2O Research Articles

PH-Dependent interaction of sulfamethoxazole with crosslinked poly(N-vinyl-2-pyrrolidone)

The sorption of sulfamethoxazole (SM) to crosslinked poly(N-vinyl-2-pyrrolidone) (CPVP) was studied by batch adsorption technique at pH's 1.0, 5.0 and 7.0 and at temperatures 10 and 30°C. Analysis by Scatchard method and Giles adsorption isotherm indicated that (i) the sorption increased in the order of pH, 7.0<1.0<5.0 and (ii) SM sorbed vertically through a monofunctional group. The peculiar sorption at pH 5.0 was explained in terms of CPVP — H2O interaction. The water-uptake by CPVP was minimum at pH 5.0 and increased at pH's 1.0 and 7.0.

SERS Observation of the Adsorption Behavior of O2, H2O, and SO2 on Silver Powder Surfaces at Nearly Real Environmental Conditions

The interaction of O2, H2O, and SO2 on silver powder prepared from the reduction of AgNO3 by NaBH4 was studied by surface-enhanced Raman scattering (SERS) at room temperature. The presence of H2O of about 103 Pa and O2 of about 104-105 Pa was necessary for observation of SERS peaks of SO32− and SO42−. The superoxide ion O2- was observed under high partial pressure for O2 conditions. SERS peaks of atomic oxygen, superoxide ion O2-, SO32−, and SO42− disappeared on evacuation. SERS peaks of surface species such as Ag2O did not disappear on evacuation.

Ab initio SCF study of the effect of Na+ and K+ ions and water on the local anaesthetic-phospholipid interaction

For gaining insight into the interactions of local anaesthetics with phospholipids, ab initio molecular orbital calculations were performed using trimethylamine and phosphate as model substances. The (OH)2OPO-···H+N(CH3)3 interaction was found comparable in strength to the (OH)2OPO-···M+ (M = Na, K) interaction and considerably stronger than the (OH)2OMPO···H2O interaction. This suggests that a major role of local anaesthetics may consist in their disturbing the P-O···H2O hydrogen bonds. Such interference may be one of the possible types of interaction between local anaesthetics and the biophase, leading to a measurable pharmacological effect.

Hydration of Fe+: A Monte Carlo simulation of water clusters and of a dilute aqueous solution

AbstractMonte Carlo statistical thermodynamic computer simulations are reported for several clusters Fe+ (H2O)n at different temperatures and for a dilute aqueous solution of Fe+ at 298 K. The energy of each configuration has been calculated in the pairwise additivity approximation using the MCY potential for the water–water interaction and an ab initio analytical potential built by us for the Fe+–H2O interaction. Energy and structural analysis of the generated configurations lead to the prediction of a coordination number of six for the first hydration shell of the Fe+ ion, both in clusters and in dilute solution. Finally, the variation in the distance to the Fe+ ion of the energy and orientation of water molecules in the solution are discussed.

ChemInform Abstract: X‐Ray and NMR Study on Cerium(III) and Magnesium(II) Perchlorate Solutions.

AbstractStructural information on the complex formation between Ce(III) and the ClO4‐ group and on ClO4‐‐H2O interactions are obtained from X‐ray scattering measurements and 35Cl NMR spectroscopy of metal‐perchlorate solutions.

A synchrotron radiation study of BaO films on W(001) and their interaction with H2O, CO2, and O2

The interaction of O2, CO2, and H2O with bulk BaO and BaO adlayers adsorbed on W(001) has been examined using ultraviolet photoelectron spectroscopy. H2O reacts with bulk BaO to form Ba(OH)2, while CO2 forms a surface layer of BaCO3. Water and carbon dioxide also react with a (√2×2)R45–BaO monolayer adsorbed on W(001) to produce adsorbed OH and CO3 species bound to the tungsten substrate. The interaction of O2 with W(001) is enhanced by the presence of a BaO monolayer on the substrate. The observations are compared with the results of previous studies.

An X-ray and NMR Study on Cerium(III) and Magnesium(II) Perchlorate Solutions

Metal-perchlorate solutions have been investigated by the X-ray scattering technique and 35Cl NMR spectroscopy. The aim of this work was to obtain structural information on the complex formation between the Cerium and the Perchlorate group and on the ClO- 4 - H2O interactions. The NMR data, the correlation functions and the analysis of the structure functions agree with the literature information about the Ce - (OClO3)z species present in aqueous solutions. Good agreement with experimental data is achieved through a model in which the Perchlorate ions are bonded as monodentate ligands to the Cerium(III). No complex formation is confirmed for Mg(II). The cations also possess a second coordination shell of water molecules. Some indications have been obtained supporting the presence of ClO- 4 - H2O contacts.

Interaction of H2O with a high-temperature superconductor.

The effect of water on the high-temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 7/ has been studied. Photoemission measurements show that water modifies valence-band states, reduces the number of inequivalent Ba sites and induces O 1s corelevel components at 534 and 531 eV. The 534-eV core-level component is coincident with that of cryosorbed ice and the enhanced 531-eV component is due to a new water-induced bonding environment in the superconductor;this is most probably a hydroxyl species. Changes in the Ba core-level appearance suggest that water may be preferentially modifying YBa/sub 2/CuO/sub 7/ in a way that affects the Ba atomic environment. The effect of water on superconductivity and its possible implications for bulk superconducting transport in ceramics is discussed. Previous reports suggesting oxygen dimerization below T/sub c/, as well as other reported changes in the spectrum, are improbable in view of these present results

The Cu+–H2O interaction potential and its application to the study of [Cu(H2O)n]+clusters at different temperatures

An analyitcal pair potential for the interaction of Cu+ ion with H2O has been obtained by fitting to quantum-mechanically calculated energies of the monohydrate Cu+–H2O. This analytical potential and Clementi's MCY potential for the H2O–H2O interaction have been used in the pairwise approximation to study [Cu(H2O)n]+ clusters, with n= 6, 8, 10, 15 and 20. This study has been performed at T= 0 K by energy minimization and at T= 50, 298 and 500 K using Monte Carlo techniques, in order to assess the effect of thermal motion. A detailed analysis of the interaction energies, the resulting radial distribution functions and the corresponding running coordination number leads to the prediction of a coordination number of six for the first hydration shell of the Cu+ ion. In this first shell the water molecules have an octahedral structure, which is slightly distorted when the temperature is increased. The reliability of these results and their validity at infinite dilution are discussed.

Non-empirical calculations for the probable coordinative binding of electron donor molecules by [AlO4] tetrahedra

Interaction of H2O, NH3 and C5H5N molecules with the aluminium atom of [AlO4] tetrahedra has been calculated by the non-empirical SCF-MO LCAO method using an STO-3G basis set. The effect of Al−O bond lengths and O−Al−O angles on the calculated characteristics of chemisorbed complexes is discussed.

Collisional broadening of rotation–vibration lines for asymmetric-top molecules. III. Self-broadening case; application to H2O

A semiclassical theory of asymmetric-top molecule line broadening, developed in part I of this series of papers for linear perturbers, is extended to asymmetric-top perturbers. This model has been successfully applied in part II to the broadening of H2O lines by N2, O2, and Ar. The present applications to the self-broadening of H2O infrared and Raman lines in the 300–900 K range also show the quality of the model. Due to the high electrostatic forces involved in the H2O–H2O interaction, the short-range anisotropic potential has little influence. Nevertheless, the need for a modeling of the trajectory is demonstrated, mainly in the case of high rotational quantum number lines.

Primary and secondary basis set superposition error at the SCF and MP2 levels. H3N--Li+ and H2O--Li+

The primary basis set superposition error (BSSE) results from the artificial lowering of the energy of each subunit of a pair by the presence of ‘‘ghost orbitals’’ of its partner. In addition, these ghost orbitals perturb the one-electron properties of the molecule, causing a change in the interaction energy, an effect known as secondary BSSE which is not corrected by the counterpoise procedure. The primary and secondary BSSE are calculated for the interactions of NH3 and H2O with Li+, using a variety of different basis sets. It is found that the 2° BSSE can be quite large, comparable in magnitude to the 1° component at both the SCF and MP2 levels. There is no basis found for the supposition that 2° BSSE improves the calculated interaction energy, nor do the 1° and 2° effects cancel one another in general. While the MP2 BSSE tends to be smaller than the SCF analog, the former can be similar in magnitude to the ‘‘true’’ MP2 contribution to the interaction; failure to remove the BSSE can hence lead to a qualitatively incorrect interpretation of the effects of electron correlation. Comparison with a system in which basis set superposition is rigorously excluded suggests that subtraction of both the full 1° and 2° BSSE is appropriate and does not overcorrect the potential. Addition of a diffuse sp shell, especially if coupled with orbital exponent reoptimization, leads to a lowering of the 1° and 2° BSSE, which moreover take on opposite sign and cancel one another to some extent.

Summary Abstract: Adsorption and interaction of O2, H2O, and CO on the NiO(100) surface

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Theoretical studies of O2−:(H2O)n clusters

AbstractThe interaction of superoxide ion O2− with up to four water molecules [O2−: (H2O)n, n = 1, 2, 4] has been investigated using ab initio molecular orbital theory. The binding energy of O2−: H2O is calculated to be −20.6 kcal/mol in good agreement with gas phase experimental data. At the MP3/6‐31G* level the O2−:H2O complex has a C2v structure with a double (cyclic) hydrogen bond between O2− and H2O. A Cs structure with a single hydrogen bond is only 0.7 kcal/mol less stable. Interaction of H2O with the doubly occupied π* orbital of O2− is preferred slightly over interaction with the singly occupied π* orbital. Natural bond orbital analysis suggests that both electrostatic and charge transfer interactions are important in anionic complexes. The charge transfer occurs predominantly in the O2− → H2O direction and is important in determining the relative stabilities of the different structures and states. Singly and doubly hydrogen‐bonded structures for the O2−: (H2O)2 and O2−: (H2O)4 clusters were found to be similar in stability and the increase in binding of the cluster becomes smaller as each additional water molecule is added to the cluster.

Supercritical fluid phase separations: Implications for detonation properties of condensed explosives

High explosive experiments offer the most extensive data on mixtures at high pressures (&amp;gt;10 GPa=100 kbar) and high temperatures (&amp;gt;1000 K). We have computed the detonation properties of two explosives, PBX-9404 (C1.4H2.75N2.57O2.69Cl0.03P0.01) and PETN (C5H8N4O12), using reliable statistical mechanical theories and realistic intermolecular potentials. The composition of the chemical species is determined by minimizing the Gibbs free energy. The calculation shows that the detonation products of explosives containing C, H, N, and O atoms can separate into N2-rich and N2-poor fluid phases and that this gas–gas phase separation can affect detonation properties at some pressures and temperatures. Since N2, CO2, and H2O molecules are major detonation products, we made a separate study on binary (N2–H2O, CO2–H2O, N2–CO2) and ternary (N2–CO2–H2O) mixtures. The results of this study show that the N2–H2O system may exhibit a fluid phase separation at pressures and temperatures relevant to a detonation environment. The predicted phase separation boundary is sensitive to the N2–H2O interaction and to the addition of CO2 molecules. We suggest static and dynamic experiments on N2–H2O mixtures that should reveal whether the predicted fluid phase separation occurs and that will help us refine the N2–H2O interaction potential.

On nickel–sulfate contacts and SO=4–H2O interactions in aqueous solutions

NiSO4 aqueous solutions are examined by x-ray diffraction. The peaks present in the G(r) correlation functions at about 2.05, 3.80, and 4.20 Å clearly indicate the existence of SO=4–H2O contacts and of two hydration shells around nickel. The absence of any peaks in the range 3.2–3.5 Å, indicates no quantitatively detectable inner sphere ion pairing between nickel and sulfate anion.

Quantum-chemical calculation of the potential surface of the OCN?-H2O interaction

The potential surface of the OCN -H2O interaction has been calculated by the SCF-MO method in the 4-31 G basis. It has been established that structures with one hydrogen bond formed by the terminal atoms of OCN are the most stable structures. The energies of the hydrogen bond, as well as the force constants and frequencies of the vibrations corresponding to the stretching of the hydrogen bond, have been calculated for a number of structures. The potential of the OCN -H2O interaction has been represented in an analytical form.

Magnetic and spectral studies on 3d-metal complexes of acetone(N-isopropylidene)tyrosyl hydrazone

Acetone(N-isopropylidene)tyrosyl hydrazone, HO-C6H4-CH2-CH(N=CMe2)-CONHN=CMe2 (ath), has been found to form adducts of the typeM (ath) Cl2·nH2O [M = Mn (II), Co (II), Ni (II), Cu (II) and Zn (II);n = 0, 1 or 2] and deprotonated complexes of the type M′(ath-2H) · 3H2O[M′ = Co(II), Ni(II) and Cu(II)]. Molar conductance studies in 0.001 Mdmso solution have indicated the non-ionic nature of the complexes. High-spin octahedral geometry for Mn(II) and Ni(II) complexes and tetrahedral geometry for Co(II) adduct have been proposed on the basis of magnetic and/or electronic spectral studies.ir spectra suggest neutral bidentate and dinegative tridentate behaviour of the ligand in the adducts and deprotonated complexes respectively,esr spectra of Cu(II) complexes indicate zero-field splitting of Cu(ath)C12 · H2O and metal-metal interaction in both the complexes.

A pseudopotential study of the hydrogen bond in H2O·H2S, H2S·H2S and H2O·H2Se systems

Intermolecular potential energy curves for the hydrogen bonded systems H2O·H2S, H2O·H2Se and H2S·H2S were calculated with nonempirical pseudopotentials using optimized-in-molecules basis sets augmented by polarization functions. The H2O·H2O interaction energy curve has been also considered as a test case. The present results for H2O·H2S and H2S·H2S indicate much weaker intermolecular interactions than those found in previous ab initio calculations. The H2O·H2Se interaction was found to be quite similar to H2O·H2S.

A b i n i t i o SCF and CI study of the NH+4⋅H2O complex

Interaction energies between a water molecule and an ammonium cation in the gas phase were computed by means of ab initio SCF and CI calculations. The influence of basis set, geometry optimization, and of electron correlation effects on the NH+4 ⋅H2O interaction energy is discussed.