Effect of procaine hydrochloride on the micellization of double tailed surfactants in the aqueous solution

The effects of procaine hydrochloride (PC) on the micellization of two kinds of double tailed surfactants in aqueous solutions, sodium bis (2-ethyl-1-hexyl) sulfosuccinate (AOT) and didodecyldimethylammonium bromide (DDAB), were studied by surface tension measurements. The results revealed that PC could decrease the equilibrium surface tension and critical micelle concentration (cmc) of AOT, but it is opposite for DDAB. Their standard thermodynamic parameters of micellization, , and , have been calculated in aqueous solutions. The locations of PC in the two kinds of micelles were investigated by UV and fluorescence spectroscopy. It is found that the mixed micelle of AOT and PC could be formed, but the effect of PC on the micellization of DDAB is quite small.     

Iron complexes of terdentate nitrogen ligands: formation and X-ray structure of three new dicationic complexes

Dicationic iron complexes were obtained upon complexation of the ligands 6,6″-di(p-tolyl)-2,2′:6′,2″-terpyridine (L¹) or 2,6-bis-(3-mesitylpyrazol-1-yl)pyridine (L²) with iron dichloride or iron trichloride. They were characterized by X-ray diffraction and FT-IR spectroscopy. Single crystal structure determinations of , and all show six-coordinate metal center. These complexes were obtained from L¹FeCl₂ and L²FeCl₂ during recrystallization attempts. (L¹)₂Fe²⁺ was shown to be a high-spin complex, whereas (L²)₂Fe²⁺ was shown to be low-spin. For , two independent dications of very similar geometry but with distinctive distortion were observed by X-ray analysis.     

Long-term prediction of compressive creep development in expanded polystyrene

The results obtained in investigating the creep of expanded polystyrene (EPS) boards under compressive stress are presented. Power and exponential equations were used for describing creep compliance. It was found that the curves of creep compliance approximated by both equations adequately represent the research results, taking into account the scatter of the experimental data. Based on the calculation and empirical estimate of long-term creep of EPS under compressive stress σ_c=(0.25–0.45)σ_10%, its creep compliance was determined for a period of 10 years in the future. The dependence of on the density of polystyrene boards and the value of long-term compressive stress σ_c was established. The expected values of creep strain development in expanded polystyrene boards EPS 80–EPS 250 under constant compressive stress σ_c=(0.25–0.45)σ_10% are presented for the prediction period of 10 years. To obtain the expected creep values for any other period of time in the interval of 5T50 years, the values of should be multiplied by the empirical coefficient .     

Pulse radiolysis of 9-anthrylmethylammonium cation in aqueous solution

The reaction of hydrated electron with 9-anthrylmethylammonium cation to form the respective anthracene radical anion in aqueous solution has been studied by the method of pulse radiolysis. The rate constant of the reaction of with is reported. It is demonstrated that the anthracene radical anion is unstable and undergoes further reactions. The spectra of transient intermediates, leading to the final reduction products, are presented.     

Rare gas–iodine complexes in the ion-pair states

Luminescence and luminescence excitation spectra in the vicinity of the optical–optical double resonance transitions to the I₂(, v_f = 8 and 9, J_f ≈ 55) levels have been measured at the bulb conditions for the I₂ + Rg mixtures (Rg = He, Ar, Xe) at the rare gas pressures 2–20 Torr and room temperature. Luminescence attributed to the RgI₂ complexes in the ion-pair states has been observed for the first time. It is argued that the complexes can be formed by direct optical excitation from the complexes or colliding pairs. Besides, the RgI₂ complexes in the ion-pair states can be formed in nonadiabatic internal conversion processes from the one. The complexes have rather long lifetime, especially in the case of Xe, and decay radiatively and nonradiatively forming I₂ molecules in different ion-pair states.     

Analysis of the interactions between human serum albumin/amphiphilic penicillin in different aqueous media: an isothermal titration calorimetry and dynamic light scattering study

The complexation process of the amphiphilic penicillins sodium cloxacillin and sodium dicloxacillin with the protein human serum albumin (HSA) in aqueous buffered solutions of pH 4.5 and 7.4 at 25 °C was investigated through isothermal titration calorimetry (ITC) and dynamic light scattering. ITC experiments were carried out in the very dilute regime and showed that although hydrophobic interactions are the leading forces for complexation, electrostatic interactions also play an important role. The possibility of the formation of hydrogen bonds is also deduced from experimental data. The thermodynamic quantities of the binding mechanism, i.e, the enthalpy, , entropy, , Gibbs energy, , binding constant, and the number of binding sites, n_i, were obtained. The binding was saturable and is characterised by Langmuir adsorption isotherms. From ITC data and following a theoretical model, the number of bound and free penicillin molecules was calculated. From Scatchard plots, and n_i were obtained and compared with those from ITC data. The interaction potential between the HSA–penicillin complexes and their stability were determined at pH 7.4 from the dependence of the diffusion coefficients on protein concentration by application of the DLVO colloidal stability theory. The results indicate decreasing stability of the colloidal dispersion of the drug–protein complexes with increase in the concentration of added drug.     

Gas-phase reactivities of charged platinum dimers with ammonia: A combined experimental/theoretical study

Computational and experimental studies of with ammonia are reported. While ammonia is dehydrogenated with either cluster type, the reaction efficiencies are quite different with  = 0.27 for [K. Koszinowski, D. Schröder, H. Schwarz, J. Phys. Chem. A 107 (2003) 4999.] and  = 0.0033 for . DFT-based relativistic calculations are consistent with this distinct behavior, with maximum energies along the reaction path of −13.3 kcal/mol for the cationic and +1.4 kcal/mol for the anionic clusters relative to the reactants. The recently proposed mechanism for the system [D. Xu. X.-Y. Chen, S.-G. Wang, Int, J. Quant. Chem. 107 (2007) 1985.] needs to be modified to account for the experimental findings.     

The limiting partial molar volume and apparent molar volume of glycylglycine in aqueous KCl solution at 298.15 and 308.15 K

Apparent molar volumes V_Φ of glycylglycine in aqueous KCl solutions have been obtained from densities at 298.15 and 308.15 K measured with a vibrating-tube densimeter. These data have been used to deduce partial molar volumes of transfer from water to different KCl–water mixtures. values are positive. This result arises from the interaction of KCl with the charged centers of glycylglycine. The results show that depends less on temperature. Hydration numbers are calculated from data and are interpreted in terms of various interactions.     

Theoretical studies on the aromaticity of η-cyclopentadienyl cobalt dithiolene complexes

Some η⁵-cyclopentadienyl cobalt dithiolene complexes CpCoS₂C₂R₂ have been optimized at B3LYP/6-311++G(d) level. The optimized geometries agree well with experiment. The analyses of nature bond orbital and nucleus-independent chemical shift (NICS) at B3LYP/6-311++G(d) and GIAO-B3LYP/6-311++G(d) levels reveal the aromatic character of the η⁵-cyclopentadienyl cobalt dithiolene complexes. However, their aromaticity is weaker than that of the isolated . There are two reasons for the change of heterocyclic aromaticity of the metal dithiolene in the η⁵-cyclopentadienyl cobalt dithiolene complexes with respect to that of the isolated . The better equalization of bond lengths in the isolated cation is the first reason. The other reason is that the contribution to the NICS from the metallic cobalt atom is much larger in the isolated cation . The planar character of cyclopentadienyl is destroyed slightly in the complexes. At the same time, the size of cyclopentadienyl (Cp) becomes bigger than the isolated Cp⁻¹ and this is caused by the cobalt atom in the pentagon. The π-electron delocalization causes stronger aromaticity of the Cp in the complexes than that of the isolated Cp⁻¹.     

Production of HO2 and O2 by multiple ionization in water radiolysis by swift carbon ions

We present a simulation of liquid water radiolysis by swift carbon ions that explicitly takes into account multiple ionization of water molecules. For high linear energy transfer (LET), this process is not negligible with respect to single ionization. The rearrangement of highly ionized water molecules is consistent with production of atomic oxygen. Multiple ionizations is shown to be responsible for creation of a large amount of radicals and O₂ molecules. The simulated yield reproduces very well direct optical measurements for swift ions with comparable LET. Our simulation for is in also agreement with experiment.     

Enthalpies of combustion and formation of 3-formylchromones

The enthalpies of combustion of 3-formylchromone (3F), 3-formyl-6-methylchromone (3F6M) and 3-formyl-6-isopropylchromone (3F6I) were determined by combustion calorimetry. The molar combustion energies () of the 3F, 3F6M and 3F6I are: −(4452.4 ± 1.8), −(5115.6 ± 2.7) and −(6411.4 ± 2.5) kJ mol⁻¹, respectively. The formation enthalpies in the crystalline state () are: −(340.2 ± 2.2), −(355.1 ± 3.1) and −(415.5 ± 3.0) kJ mol⁻¹, respectively.s     

QSAR study on N-containing corrosion inhibitors: Quantum chemical approach assisted by topological index

In this paper, QSAR study on N-containing corrosion inhibitors has been made using quantum chemical approach assisted by a novel topological index (). Two models were obtained and their efficiency was examined using statistics. The results indicate that inhibition efficiencies relate to some parameters of corrosion inhibitors, such as E_homo, polarizability, Dipole, frontier orbital charge density, the interaction mode between inhibitors and metal surface (feedback donor–acceptor coordination bonds), (steric hindrance of molecules). Predicted values are consistent with the experimental ones on the whole. The residuals range within the experimental error. So the models can be used to predict inhibition efficiencies of the same type molecules.     

Computational study on the kinetics of the reaction between Ca and urea

A computational study, in the framework of statistical kinetic theories, of the reaction of Ca²⁺ with urea has been carried out. The kinetically preferred products are NH₃ + [CaOCNH]²⁺, which are the fifth products in order of stability. The second kinetically preferred products are , followed by [CaNH₃]²⁺+HNCO, whereas the most stable ones, and , appear only in residual quantities. These estimates are in agreement with the experimental evidence and provide a suitable mechanism to understand the competition between Coulomb explosion and neutral loss processes.     

Rate constants of the O(D) reactions with N2, O2, N2O, and H2O at 295 K

Using a technique of laser flash photolysis coupled with vacuum ultraviolet laser-induced fluorescence spectroscopy, the rate coefficients of O(¹D) reactions with N₂, O₂, N₂O, and H₂O at 295 ± 2 K have been determined to be , k_O2=(4.06±0.24)×10^-11, k_N2O=(1.35±0.08)×10^-10 and . The quoted uncertainties include estimated errors and are the 95% confidence level. The k_N2 and k_N2O values obtained are larger than the current NASA/JPL recommendations by 26% and 16%, respectively, although they are still within the error limits associated with the recommendations.     

To what extent are thermodynamic properties of water argon-like?

A new view on the role of H-bonds in water, arising from the principle of corresponding states and Hilbert’s principle is presented. It is shown that the relative values of the H-bond contributions to the fraction volume and the heat of evaporation per molecule do not exceed 5%, although H-bonds are responsible for the non-monotone behavior of the fraction volume. It is established that the average number of H-bonds per molecule everywhere on the vapor–liquid coexistence curve is given by the formula n_H(T) ≈ 4(1 − 0.83t), where and is the critical temperature of water.     

Hydrodynamic effects on the oscillations of supported bubbles: implications for accurate measurements of surface properties

Oscillating bubble techniques are commonly used to infer dynamic surface tensions (DST) from the measurements of the dynamic pressure differences across an interface. In inferring DST from such measurements, it is assumed that hydrodynamic efects either are negligible or can be approximated. In virtually all previous studies, the dynamic bubble shapes, which are set by the requisite balance of forces at the bubble surface, are taken to be nearly spherical and assumed to be governed by the static Young–Laplace (Y–L) equation alone. To examine these assumptions, the Navier–Stokes and continuity equations governing the flow of a liquid outside an axisymmetric bubble supported by a narrow capillary are solved simultaneously by a rigorous finite element method. Cases of constant surface tension (pure liquids or solutions with very fast adsorption) are tested to focus on understanding the effects of fluid motion on surface tension measurements. To test the capability of the computational algorithm on describing the hydrodynamics, computed and experimental velocity profiles are compared and found to be consistent, as are the apparent surface tensions. Parameters such as forcing frequency, forcing amplitude, chamber dimensions, and surface tension and viscosity of the liquid are varied to find the limits where pulsating bubbles depart from spherical and where hydrodynamic effects impact the determination of surface tension. In the commercial pulsating bubble surfactometer (PBS), the bubble shapes remain nearly spherical for low pulsation or oscillation rates (≤ 100 Hz) with moderate volume amplitudes. Under these conditions, however, two major hydrodynamic effects, due to the inertia of the bulk liquid, or to the liquid viscosity and the viscous forces acting on the chamber walls, are found to be important and can cause large errors in the surface tension measurements. For measurements of low surface tensions (≤ 5 mN/m) in a PBS, oscillating bubble methods that do not take into account shape deformations from the spherical are found to be inaccurate, and the results from dynamic bubble shape analysis (solving the Y–L equation for a nonspherical axisymmetric surface) are shown to provide another approach to obtain accurate results provided that hydrodynamic effects can be neglected. At higher frequencies (≥ 200 Hz), because of strong convection around the surface of the bubble, the bubble shapes become highly deformed. Further extensions of this algorithm are needed, to include the surfactant diffusion and adsorption effects by which the surface tension may change with time.     

Transport properties of acetone aqueous solutions: molecular dynamics simulation and NMR studies

Two quantities η_rel and are applied to study the nonideal acetone–water association mixture. An all-atom acetone model and a TIP5P water model have been adopted for molecular dynamics simulation. We study the transport properties of the system comparing the 's of strong hydrogen bond and weak contact based on transport properties, MD simulations together with NMR experimental data and find good agreement of concentration dependence, which exhibits the cooperation effect.     

Electrochemical genosensing properties of gold nanoparticle–carbon nanotube hybrid

We have investigated the electrochemical genosensing properties of gold nanoparticle–carbon nanotube hybrid. Thiolated oligonucleotide probes and mercaptohexanol were self-assembled onto the Au–CNT hybrid. The hybridization events of target oligonucleotides are monitored using electrochemical impedance spectroscopy, cyclic voltammetry and a.c. voltammetry techniques. A redox-active mediator is used to detect the oxidation of guanine residues. The as-fabricated genosensor is able to differentiate between complementary and mismatched hybridizations, relying on the oxidation current of the guanine residues mediated via .     

Theoretical studies on fluorescence of phenol and 1-naphthol in both acid and alkali solutions

The molecular structures of the ground state and the first singlet excited state for , C₆H₅OH, C₆H₅O⁻, , C₁₀H₇OH and C₁₀H₇O⁻, the forms of phenol and 1-naphthol in acid and alkali solutions, were optimized by ab initio HF and configuration interaction with singlet excitations (CIS) method, respectively. Their fluorescent spectra were obtained by the time-dependent density functional theory (TD-DFT) using the B3LYP method with the 6-31+G (d) basis set. The frontier molecular orbital characteristics, fluorescent spectrum and proton affinities had been analyzed systematically in order to study different fluorescence of phenol and 1-naphthol in acid and alkali solutions. It was found that C₆H₅OH and are the main forms of phenol in acid solution, but C₆H₅O⁻ in alkali solution; C₁₀H₇OH and C₁₀H₇O⁻ are the main forms of 1-naphthol in alkali solution, but in acid solution. The calculated results are in good agreement with the experimental data.     

Structure characterization of several oxalate-bridged transition-metal coordination polymers

Four oxalate-bridged transition-metal supramolecular compounds [Co₂(im)₄(ox)₂] 1, [Co(im)₂(ox)] 2, [Mn(2,2′-bpy)(ox)] 3 and [Fe(H₂O)₂(ox)] 4 (im, imidazole; ox, oxalate; bpy, bipyridine) were obtained from the simple hydrothermal reactions of Mⁿ⁺oxL (M, transition metal; L, aromatic N-donor ligand) system. They all exhibit the 1-D chain structures, consisting of the (or ML²⁺) units linked by oxalate bridges. Interestingly, the 1-D oxalate chains in the title compounds are further self-assembled into the 3-D supramolecular networks through the interchain various secondary bonding interactions. Because the units adopt the different configuration, the oxalate chains show either zigzag type as in compounds 1–3 or linear type as in compound 4. Compounds 1 and 2 are isomeric, and only in packing modes of interchain im molecules there exists the difference.