Enantioselectively catalyzed oxidation of 3,4-dihydroxy-l-phenylalanine by N-lauroyl L or D-histidine-Cu(II) complex in CTABr micelles.

In order to investigate the enzyme model reaction the oxidation of 3,4-dihydihydroxy-L-phenylalanine(L-DOPA) was carried out using optically active catalyst, N-lauroyl L or D-histidine-Cu(II) complex(L or D-LauHis-Cu(II)), showing appreciable enantioselectivity in the presence of the mixed micelles with CTABr.     

Production of poly(methyl methacrylate) particles by dispersion polymerization with mercaptopropyl terminated poly(dimethylsiloxane) stabilizer in supercritical carbon dioxide

Poly(methyl methacrylate) (PMMA) particles were produced by dispersion polymerization of methyl methacrylate in the presence of mercaptopropyl terminated poly(dimethylsiloxane) (MP-PDMS) in supercritical carbon dioxide at about 30 MPa for 24 h at 65 °C. The particle diameter could be controlled in a size range of submicron to micron by varying MP-PDMS concentration. The MP-PDMS worked as not only a chain transfer agent but also a colloidal stabilizer, which was named tran stab.Part CCLI of the series Studies on suspension and emulsion     

Extrathermodynamic study of surface diffusion in reversed-phase liquid chromatography with silica gels bonded with alkyl ligands of different chain lengths

Surface diffusion on adsorbents made of silica gels bonded to C1, C4, C8, and C18 alkyl ligands was studied in reversed-phase liquid chromatography (RPLC) from the viewpoints of two extrathermodynamic relationships: enthalpy-entropy compensation (EEC) and linear free-energy relationship (LFER). First, the values of the surface diffusion coefficient (D(s)), normalized by the density of the alkyl ligands, were analyzed with the modified Arrhenius equation, following the four approaches proposed in earlier research. This showed that an actual EEC resulting from substantial physicochemical effects occurs for surface diffusion and suggested a mechanistic similarity of molecular migration by surface diffusion, irrespective of the alkyl chain length. Second, a new model based on EEC was derived to explain the LFER between the logarithms of D(s) measured under different RPLC conditions. This showed that the changes of free energy, enthalpy, and entropy of surface diffusion are linearly correlated with the carbon number in the alkyl ligands of the bonded phases and that the contribution of the C18 ligand to the changes of the thermodynamic parameters corresponds to that of the C10 ligand. The new LFER model correlates the slope and intercept of the LFER to the compensation temperatures derived from the EEC analyses and to several parameters characterizing the molecular contributions to the changes in enthalpy and entropy. Finally, the new model was used to estimate D(s) under various RPLC conditions. The values of D(s) that were estimated from only two original experimental D(s) data were in agreement with corresponding experimental D(s) values, with relative errors of approximately 20%, irrespective of some RPLC conditions.     

Single-bubble sonochemiluminescence in aqueous luminol solutions

Sonochemiluminescence (SCL) of luminol due to a single bubble is studied through spectral measurement. No SCL was observed from a stable single bubble that emitted high-intensity sonoluminescence (SL). In contrast, SCL was observed under conditions of an unstable dancing bubble, where a bubble grows and ejects tiny bubbles, making it "dance" by counteraction. Furthermore, SCL was observed from dancing bubbles even when SL was not observed, depending on the dissolved gas content. The instability of bubble collapse is the key parameter governing SCL.     

Selective permeation of CO2 through poly 2-(N,N-dimethyl)aminoethyl methacrylate membrane prepared by plasma-graft polymerization technique

A membrane having an amine moiety was prepared by plasma-grafting 2-(N,N-dimethyl)aminoethyl methacrylate (DAMA) onto a microporous polyethylene substrate. Permselectivity of the membrane for CO₂ over N₂ was achieved in both dry and water swollen conditions. When the CO₂ partial pressure in the feed gas was 0.047 atm, the selectivity of CO₂ over N₂ reached 130 for the highly swollen water containing membrane. This value was found to agree with that obtained with a mobile carrier membrane (supported liquid membrane) using DAMA as the carrier. The effects of several experimental conditions such as degree of grafting, feed partial pressure and temperature on the membrane performance were studied. It was suggested that the membrane acted as a fixed carrier membrane for CO₂ facilitated transport in under the dry condition and acted as a fixed reaction site membrane in the water swollen condition. The carrier transport mechanism is discussed for dry and aqueous membranes.     

Double bond isomerization of 5-vinylbicyclo[2.2.1]hept-2-ene to 5-ethylidenebicyclo[2.2.1]hept-2-ene over alkaline earth oxides

All the alkaline earth oxides exhibit activities for double, bond isomerization of 5-vinylbicyclo[2.2.1]hept-2-ene (VBH) to 5-ethylidenebicyclo[2.2.1]hept-2-ene (EBH) at a reaction temperature of 273 K. The order of the activity on the basis of unit weight of catalyst was CaO>MgO>SrO>BaO when compared under optimum pretreatment conditions. The E/Z ratio in the products is determined by the reaction temperature regardless of the type of catalyst; the ratios were 82/18 and 88/12 for the reaction temperatures of 323 and 273 K, respectively.     

Synthesis and Rearrangement of P‐Nitroxyl‐Substituted PIII and PV Phosphanes: A Combined Experimental and Theoretical Case Study

Low‐temperature generation of P‐nitroxyl phosphane 2 (Ph₂POTEMP), which was obtained by the reaction of Ph₂PH ( 1 ) with two equivalents of TEMPO, is presented. Upon warming, phosphane 2 decomposed to give P‐nitroxyl phosphane P‐oxide 3 (Ph₂P(O)OTEMP) as one of the final products. This facile synthetic protocol also enabled access to P‐sulfide and P‐borane derivatives 7 and 13 , respectively, by using Ph₂P(S)H ( 6 ) or Ph₂P(BH₃)H ( 11 ) and TEMPO. Phosphane sulfide 7 revealed a rearrangement to phosphane oxide 8 (Ph₂P(O)STEMP) in CDCl₃ at ambient temperature, whereas in THF, thermal decomposition of sulfide 7 yielded salt 10 ([TEMP‐H₂][Ph₂P(S)O]). As well as EPR and detailed NMR kinetic studies, indepth theoretical studies provided an insight into the reaction pathways and spin‐density distributions of the reactive intermediates.     

Pulsed EPR Dipolar Spectroscopy under the Breakdown of the High-Field Approximation: The High-Spin Iron(III) Case

Pulsed EPR dipolar spectroscopy (PDS) offers several methods for measuring dipolar coupling and thus the distance between electron-spin centers. To date, PDS measurements to metal centers were limited to ions that adhere to the high-field approximation. Here, the PDS methodology is extended to cases where the high-field approximation breaks down on the example of the high-spin Fe³⁺/nitroxide spin-pair. First, the theory developed by Maryasov et al. (Appl. Magn. Reson. 2006 , 30, 683–702) was adapted to derive equations for the dipolar coupling constant, which revealed that the dipolar spectrum does not only depend on the length and orientation of the interspin distance vector with respect to the applied magnetic field but also on its orientation to the effective g-tensor of the Fe³⁺ ion. Then, it is shown on a model system and a heme protein that a PDS method called relaxation-induced dipolar modulation enhancement (RIDME) is well-suited to measuring such spectra and that the experimentally obtained dipolar spectra are in full agreement with the derived equations. Finally, a RIDME data analysis procedure was developed, which facilitates the determination of distance and angular distributions from the RIDME data. Thus, this study enables the application of PDS to for example, the highly relevant class of high-spin Fe³⁺ heme proteins.     

Preparation of free‐standing silicone particles in aqueous heterogeneous system

To prepare cross‐linked silicone (silicone rubber) particles in an aqueous medium, we investigated two synthesis methods involving a miniemulsion system. The first method was based on cationic ring‐opening polymerization of cyclic siloxane, which is a common synthetic route for linear silicone oil and uses octamethylcyclotetrasiloxane (D₄) as the monomer and dimeric D₄ (bis‐D₄) as the cross‐linker. Although this method produces silicone particles, the particles do not remain in the particulate state after drying because of low cross‐linking density. The polymerization mechanism of this method was also investigated, which proceeds under the ring‐opening reaction of D₄ in monomer droplets and upon polycondensation of hydrolyzed D₄, which occurs in the water phase (ie, outside the monomer droplets). This mechanism implied that introducing the cross‐linking structure into particles is difficult because of the low solubility of bis‐D₄ in water. To overcome these difficulties, we demonstrated a second method of preparing silicone particles based on the thiol‐Michael addition reaction between thiol‐terminated silicone oil and triacrylate in miniemulsion systems. Transmission electron microscopy images indicated that the silicone particles obtained in the particulate state upon drying and the aggregates of these particles showed elasticity.