Estimation of local density augmentation and hydrogen bonding between pyridazine and water under sub- and supercritical conditions using UV-vis spectroscopy.

The local density around pyridazine was evaluated by examining the UV-vis spectral shift of pyridazine in a high-pressure liquid state and supercritical water from 25 to 450 degrees C and from 20 to 45 MPa. Augmentation of the local density was observed from 380 to 420 degrees C, and showed the maximum at a lower density than the critical density of water. The degree of hydrogen bonding was estimated in consideration of the local density augmentation. The estimated degree of hydrogen bonding under subcritical conditions without any difference between the local density and the bulk density corresponded to the previously reported results with a UV-vis absorbance spectral shift of quinoline and an NMR proton chemical shift. However, the degree of hydrogen bonding near the critical point of water was larger than that in the case that the local density augmentation was not taken into account. At 380 degrees C and 0.2 g cm(-3) of the bulk density there are 30% as many hydrogen bonds as those under the ambient condition, and it was around 1.5-times that without considering local-density augmentation.     

Organic-ligand-assisted supercritical hydrothermal synthesis of titanium oxide nanocrystals leading to perfectly dispersed titanium oxide nanoparticle in organic phase

Titanium oxide (TiO₂) nanocyrstals which are perfectly dispersed in organic solvents are synthesized by organic-ligand-assisted supercritical hydrothermal synthesis. The addition of hexaldehyde to the supercritical hydrothermal synthesis of TiO₂ leads to the in-situ surface modification, which enables the synthsized TiO₂ nanocrystals to be perfectly dispersed in iso-octane because of its hydrophobic nature. Further, the one-pot synthesis of hybrid materials results in the significant reduction of the particles size, probably due to the capping effect of hexaldehyde to suppress the particles growth.     

Ab initio calculations of structures and interaction energies of toluene dimers including CCSD(T) level electron correlation correction

The intermolecular interaction energy of the toluene dimer has been calculated with the ARS-F model (a model chemistry for the evaluation of intermolecular interaction energy between ARomatic Systems using Feller's method), which was formerly called as the AIMI model III. The CCSD(T) (coupled cluster calculations with single and double substitutions with noniterative triple excitations) interaction energy at the basis set limit has been estimated from the second-order Moller-Plesset perturbation interaction energy at the basis set limit obtained by Feller's method and the CCSD(T) correction term obtained using a medium-size basis set. The cross (C(2)) dimer has the largest (most negative) interaction energy (-4.08 kcal/mol). The antiparallel (C(2h)) and parallel (C(S)) dimers (-3.77 and -3.41 kcal/mol, respectively) are slightly less stable. The dispersion interaction is found to be the major source of attraction in the toluene dimer. The dispersion interaction mainly determines the relative stability of the stacked three dimers. The electrostatic interaction of the stacked three dimers is repulsive. Although the T-shaped and slipped-parallel benzene dimers are nearly isoenergetic, the stacked toluene dimers are substantially more stable than the T-shaped toluene dimer (-2.62 kcal/mol). The large dispersion interaction in the stacked toluene dimers is the cause of their enhanced stability.     

Mechanical stabilities of K4 carbon and K4-like NaC2

The mechanical stabilities of K₄ carbon and K₄-like NaC₂ have been studied by performing first-principle calculations. Total energies as functions of isotropic deformations and volume-conserving tetragonal and trigonal deformations have been calculated. For K₄ carbon, the total energy shows a minimum for isotropic and trigonal deformations, but exhibits maxima for tetragonal deformation. In contrast, the total energy of K₄-like NaC₂ shows a minimum under all three deformations. These results indicate that K₄ carbon is not a metastable phase, but that K₄-like NaC₂ is a metastable phase. In addition, the heat of formation of K₄-like NaC₂ is discussed.     

Oleic acid-enhanced dissolution of cellulose in high-temperature water

This paper reports, for the first time, the enhanced dissolution of cellulose in subcritical water by addition of a fatty acid. Simply adding oleic acid dramatically promoted the dissolution of cellulose. High-pressure in-situ observation showed that cellulose dissolved in high-temperature water at approximately 500 K, which is 70 K lower than without oleic acid. The yield of oligo and monosaccharides with oleic acid at 473 K was seven times higher than without oleic acid.     

Synthesis and morphology control of surface functionalized nanoscale yttrium aluminum garnet particles via supercritical hydrothermal method

Organic-functionalized nanoscale yttrium aluminum garnet (YAG) particles were synthesized via a simple rapid supercritical hydrothermal method in the presence of oleylamine and oleic acid as organic surface modifiers. The presence of the organic molecules resulted in the various morphologies of the produced YAG particles, including cubic, spherical and chainlike structures. Because of their hydrophobic surface character, as-synthesized particles were dispersible in organic solvents.     

Novel high-strength,micro fibrillated cellulose-reinforced polypropylene composites using a cationic polymer as compatibilizer

Novel high-strength, micro-fibrillated cellulose (MFC)-reinforced polypropylene (PP) composites were prepared using maleic anhydride polypropylene (MAPP) and a cationic polymer having a primary amino group (CPPA) as coupling agents. Un-dried kraft pulp was micro-fibrillated into nano- to submicron-wide fibrils by kneading with powdered PP and the coupling agents via a twin-screw extruder. The composites were prepared by injection molding. The MFC-reinforced PP composites containing both coupling agents MAPP and CPPA (combination system) showed extremely high mechanical strength compared with the MFC-reinforced composite containing only MAPP. The tensile strength of a 30 wt% MFC-PP composite containing the combination system was 27 % higher than that of the composite containing only MAPP, and more than 60 % higher than that of neat PP. In addition, the heat distortion temperature, under a 1.82-MPa flexural load, of the composite with the combination system was 17 °C higher than that of the composite with MAPP only, and 34 °C higher than that of neat PP. The anisotropy of the modulus and strength in the injection-molded MFC composites was lower than that of glass fiber-reinforced PP.     

C?H bond dissociation enthalpies of fluorinated formates and estimation of their rate constants for the reactions with OH radicals: A DFT study

Density functional theory was used to estimate the lifetime of fluorinated formates, which are primary products from the oxidation of hydrofluoroethers. First, the C? H bond dissociation enthalpies (BDEs) of 10 fluorinated formates, C_nF_{2n + 1}OC(O)H (n = 1–4) and C_nHF_2nOC(O)H (n = 1–3) have been calculated by using the density functional theory with (RO)B3LYP/6‐311G(d,p). Secondly, from these computed BDEs, the rate constants k_OH of the hydrogen abstraction reaction between the fluorinated formates and OH radicals have been estimated using the formulation proposed by Heicklen (Int. J. Chem. Kinet. 13 , 651, 1981). We modified the formulation proposed by Heicklen in order to relate BDEs to k_OH for formates based on the results of the ab initio studies using standard transition state theory with the G2(MP2) level. Consequently, the k_OH of all the formates considered here are estimated to be around 1.5–4.7 × 10^?14 cm³ molecule^?1 s^?1 at 298 K. Their lifetimes concerning with the decomposition by OH radicals (τ_OH) in atmosphere have been evaluated as 0.4–4.5 years from the estimated k_OH. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 524–530, 2002     

New steroid‐group‐containing borazine compounds and their 13C NMR spectra

New borazine compounds containing steroid units (cholesteryl and stigmasteryl) were prepared by the reactions of B,B′,B″‐trichloro‐N,N′,N″‐trimethylborazine with the 3‐chloro derivatives of the corresponding steroids under Grignard conditions. The products were characterized by ¹³C–¹H correlation NMR measurements to give fully assigned ¹³C NMR data. Copyright © 2001 John Wiley & Sons, Ltd.     

Synthesis of 24,24-difluoro- and 24ξ-fluoro-25-hydroxyvitamin D3

From cholenic acid 24,24-difluoro-25-hydroxyvitamin D₃ and 24ξ-fluoro-25-hydroxyvitamin D₃ were prepared.