Hydrophilic quaternary ammonium type ionic liquids. Systematic study of the relationship among molecular structures, osmotic pressures, and water-solubility

This Letter examines the relationship between the structures of ionic liquids and their water-solubility or osmotic pressure with a number of synthesized quaternary ammonium type ionic liquids and organic salts containing a hydroxyl group as hydrophilic substituted groups on ammonium group cations, and bromide or methylsulfonate as anions. The study found a linear relation between the amount and osmotic pressure of the water-soluble ionic liquids synthesized here, strongly indicating that these water-soluble ionic liquids are perfectly ionized in water like inorganic salts with small diameter ions.     

Analyses of lepidopteran sex pheromones by mass spectrometry

Lepidoptera, including about 150,000 species in the world, comprise the second largest insect group, and sex pheromones have been identified from virgin female moths of more than 600 species. The chemical structures are simple, but diverse, because species-specific pheromones play an important role in the reproductive isolation of each species. The pheromone content in each female is quite low, and gas chromatography coupled to mass spectrometry (GC-MS) is most frequently utilized to reveal the chemical structure. Almost all pheromone components are straight-chain compounds and are classified into two major groups [i.e. unsaturated C₁₀-C₁₈ fatty alcohols and their derivatives (Type I) and C₁₇-C₂₃ polyenyl hydrocarbons and their epoxides (Type II)]. In addition to the unbranched compounds, some species secrete methyl-branched compounds (e.g., 2-ketones). For the identification of these compounds, determining the positions of the double bond, the epoxy ring, and the methyl group is an important key step. Copious spectral information measured by electron-impact ionization (70 eV) has been accumulated for these compounds. This review therefore deals with their spectral characteristics, namely, diagnostic ions, to apply them to pheromone studies on new target insects.     

Thermodynamic properties of methane/water interface predicted by molecular dynamics simulations

Molecular dynamics simulations have been performed to examine the thermodynamic properties of methane/water interface using two different water models, the TIP4P/2005 and SPC/E, and two sets of combining rules. The density profiles, interfacial tensions, surface excesses, surface pressures, and coexisting densities are calculated over a wide range of pressure conditions. The TIP4P/2005 water model was used, with an optimized combining rule between water and methane fit to the solubility, to provide good predictions of interfacial properties. The use of the infinite dilution approximation to calculate the surface excesses from the interfacial tensions is examined comparing the surface pressures obtained by different approaches. It is shown that both the change of methane solubilities in pressure and position of maximum methane density profile at the interface are independent of pressure up to about 2 MPa. We have also calculated the adsorption enthalpies and entropies to describe the temperature dependency of the adsorption.     

Synthesis of acetic acid from methanol alone by homogeneous metal complex catalyst. Part 4. In-situ formation of catalyst species and halogen effect in the RuCl3·3H2O–SnX2 (X=F, Cl, Br, I) composite system

Highly selective formation of methyl acetate has been found possible from methanol alone using the catalyst generated in situ from RuCl₃·3H₂O and SnCl₂ as well as SnX₂ (X=F, Br, I). The reaction did not occur in the absence of SnCl₂ added and the optimum [Sn]/[Ru] ratio appeared at about 16. The halogen effect showed the order of SnF₂>SnCl₂>SnBr₂>SnI₂, which indicates the importance of cationic character of Ru(II) center to facilitate its electrophilic interaction with β-hydrogen of Ru–OCH₃ intermediate in the rate-limiting dehydrogenation step.     

Size-specific reactions of copper cluster ions with a methanol molecule

Chemisorption of a methanol molecule onto a size-selected copper cluster ion, Cu(n)+ (n = 2-10), and subsequent reactions were investigated in a gas-beam geometry at a collision energy less than 2 eV in an apparatus based on a tandem-type mass spectrometer. Mass spectra of the product ions show that the following two reactions occur after chemisorption: dominant formation of Cu(n-1)+(H)(OH) (H(OH) formation) in the size range of 4-5 and that of Cu(n)O+ (demethanation) in the size range of 6-8 in addition to only chemisorption in the size range larger than 9. Absolute cross sections for the chemisorption, the H(OH) formation, and the demethanation processes were measured as functions of cluster size and collision energy. Optimized structures of bare copper cluster ions, reaction intermediates, and products were calculated by use of a hybrid method (B3LYP) consisting of the molecular orbital and the density functional methods. The origin of the size-dependent reactivity was explained as the structural change of cluster, two-dimensional to three-dimensional structures.     

Switchable rewritability of Ag-TiO2 nanocomposite films with multicolor photochromism

The photochromism and rewritability of Ag-TiO2 films were deactivated by modification with thiols to make it possible to retain color images displayed on the films (for more than 3 days under white fluorescent lamps), while the deactivated properties were fully reactivated by UV-irradiation.     

Giant reduction in dynamic modulus of kappa-carrageenan magnetic gels

Effects of magnetization on the complex modulus of kappa-carrageenan magnetic gels have been investigated. The magnetic gel was made of a natural polymer, kappa-carrageenan, and a ferrimagnetic particle, barium ferrite. The complex modulus was measured before and after magnetization of the gel by dynamic viscoelastic measurements with a compressional strain. The gels showed a giant reduction in the storage modulus of approximately 10(7) Pa and also in the loss modulus of approximately 10(6) Pa due to magnetization. The reduction increased with increasing volume fraction of ferrite, and it was nearly independent of the frequency. It was also found that the change in the modulus was nearly independent of the magnetization direction and irradiation time of the magnetic fields to the gel. The magnetic gels demonstrating the giant reduction in the dynamic modulus showed a large nonlinear viscoelastic response. It was observed that the magnetic gel was deformed slightly due to magnetization. The observed giant complex modulus reduction could be attributed to the nonlinear viscoelasticity and deformation caused by magnetization. Magnetism, nonlinear viscoelasticity, and effects of magnetization on the morphological and shape changes were discussed.     

Size effects of gold nanaoparticles on plasmon-induced photocurrents of gold-TiO2 nanocomposites

An ITO electrode was coated with a nanoporous TiO2 film, and the film was loaded with Au nanoparticles with different diameters (15, 40 and 100 nm). The electrode exhibited plasmon-induced photocurrents in the presence of Fe(2+/3+) couple under visible light (lambda > 420 nm). The quantum efficiency increased with increasing particle size, whereas the maximum photocurrent density decreased.