Effect of dose rate on the radiation-induced polymerization of ethylene in tert-butyl alcohol

The dependence of the dose rate on the rate of radiation-induced polymerization of ethylene in tert-butyl alcohol containing 5 vol-% water was studied. The reaction was carried out by use of a reactor with a capacity of 100 ml under the following conditions: pressure, 200 kg/cm²; temperature, 24 ± 3°C; dose rate, 3.7 × 10⁴?1.6 × 10⁵ rad/hr; amount of medium, 70 ml. The dose rate exponents for rate of the polymerization, the molecular weight, and the number of polymer chain were found to be about 0.8, ?0.1, and 0.9, respectively. These results were well explained with kinetic results (obtained by a novel analytical method) for the polymerization which contain both first-order and second-order terminations for the concentrations of propagating radical. The individual values of the rate constants in each elementary reaction were also obtained.     

Chiral separation of trimetoquinol hydrochloride and related compounds by micellar electrokinetic chromatography using sodium taurodeoxycholate solutions and application to optical purity determination

The chiral separation of trimetoquinol hydrochloride, which is a bronchodilator (Inolin), and three related compounds by micellar electrokinetic chromatography was investigated using a bile salt as a chiral surfactant. Enantiomers of these compounds, except laudanosoline, were successfully separated within 12 min using a separation tube of effective length 500 mm × 0.05 rum i.d. and a 0.05 M sodium taurodeoxycholate solution of pH 7.0. The observed theoretical plate numbers of the peaks were ca. 150000. Chiral recognition was affected by the structure of bile salts, the pH of the buffer solutions used and the structure of the solutes. Of four kinds of bile salts, successful chiral separation was achieved only using sodium taurodeoxycholate solution under neutral conditions. The method was applied to the optical purity determination of trimetoquinol hydrochloride. The effects of surfactant concentrations and some additives to the micellar solution are briefly described.     

Photoelectron kinetic energy dependence in near threshold ionization of NO from A state studied by time-resolved photoelectron imaging

Photoelectron angular distributions in the laboratory frame (LF-PADs) from the A((2)sigma(+)) state of NO molecule were measured by femtosecond time-resolved photoelectron imaging with (1 + 1(')) resonance enhanced multiphoton ionization via the A state. High-precision measurements of the anisotropy parameters of LF-PADs were performed for the photoelectron kinetic energy from 0.03 to 1.05 eV as a function of the pump-probe delay time. The revival feature of the rotational wave packet on the A state was clearly observed in the time dependence of the photoelectron anisotropy parameters. By approximating the phase shifts of the photoelectron partial waves by the quantum defects in the high-lying Rydberg states using the multichannel quantum defect theory, the energy-dependent photoionization transition dipole moments were determined, for the first time, from time-dependent LF-PADs measured by time-resolved photoelectron spectroscopy.     

Synthesis and photoluminescence properties of BF2 complexes with 1,3-diketone ligands

BF₂ complexes with 1,3-diketone ligands were synthesized, and their optical and electrochemical properties were studied. The colors of the complexes varied depending on the structures of the 1,3-diketone ligands. The absorption and emission maxima of the complexes with 1,3-diaryl-1,3-diketone ligands were considerably red shifted as compared to those of the complexes with 1-aryl-3-trifluoromethyl-1,3-diketone ligands, suggesting an extended π-conjugation of the 1,3-diaryl-1,3-diketone moieties. The molar absorption coefficients and quantum yields of the complexes with 1,3-diaryl-1,3-diketone ligands were larger than those of the complexes with 1-aryl-3-trifluoromethyl-1,3-diketone ligands. Cyclic voltammetry measurements revealed that the reduction potentials of the BF₂ complexes were higher than those of the free ligands. These complexes exhibited various emission colors in the solid states due to the intermolecular interactions.     

R3Al-R'3SiOTf: novel and powerful reagent system for stereospecific alkylation-silylation reactions of epoxides

[reaction: see text] A novel and powerful reagent system R(3)Al-R'(3)SiOTf for the one-pot alkylation-silylation reaction of epoxides was discovered, and the reactions of various epoxides with the new reagent system have been demonstrated to occur stereospecifically giving rise to the corresponding alkylation-silylation products in excellent yields.     

Diinsertion of fluorenylidene into a sulfur-sulfur bond of diaryl disulfides

Upon irradiation (>340 nm) of a benzene solution of diazofluorene with di-p-tolyl- or di-p-anisyl disulfide, the corresponding 9,9′-bis(arylmercapto)bifluorenyl was afforded in moderate to good yield accompanied by formation of 9,9′-bis(arylmercapto)fluorene. The major reaction pathway is considered to be a disulfur ylide formation followed by two times of successive Stevens rearrangement or by concerted electron redistribution via [2,3]sigmatropic rearrangement.     

Effect of amount of monomer on radiation-induced polymerization of styrene adsorbed on silica gel

The effect of amount of monomer on radiation-induced polymerization of styrene adsorbed on silica gel was investigated with the monomer amounting from less than monolayer adsorption to more than the equilibrium adsorption. The rate of graft polymerization and the molecular weight of the polymer changed with the amount of monomer adsorbed on silica gel. Maximum grafting efficiency was obtained at monolayer adsorption. The molecular weight of graft polymer was higher than that of homopolymer in both radical and cationic polymerizations, and the ratio in molecular weight of graft polymer to that of homopolymer tends to be unity with increasing amount of adsorbed monomer. These results can mainly be explained in terms of the number of initiating species (radical and cation) that change in relation to the amount of adsorbed monomer. Propagation and termination change with amount of adsorbed monomer in relation to the molecular mobility of adsorbed monomer. A very high-molecular-weight graft polymer is formed only with a small amount of adsorbed monomer in the initial stage. The grafting percent with a large amount of adsorbed monomer increased after most of the monomer has been polymerized. Secondary effect of radiation on the graft and homopolymers due to energy transfer from silica gel is suggested from the complicated phenomena in the later stage of the reaction.     

Enhancement of sonochemical reaction of terephthalate ion by superposition of ultrasonic fields of various frequencies

The ultrasonic reactor with dual frequency was used and the effect of frequency on the fluorescence intensity of terephthalate ion was experimentally investigated in the frequency range from 176 to 635 kHz. The sonochemical reaction fields were visualized by using sonochemical luminescence of luminol solution. Compared with the fluorescence intensity of terephthalate ion for single frequency, the fluorescence intensity for dual frequency increased. The fluorescence intensity ratio of dual frequency to single frequency had maximum value when the frequency of transducer attached at the bottom wall was comparable in magnitude to that at the side wall. In the case of dual frequency, the sonochemical reaction fields became more extensive in the reactor and more intensive around the center of the reactor.     

Synthesis,Redox Properties,and Electronic Spectra of Sterically Crowded Triarylphosphines Conjugated with Electron Acceptors

Abstract

Synthesis, redox properties, and electronic spectra of the sterically crowded triarylphosphines conjugated with π-electron systems, especially electron acceptors such as carbonyl group, are briefly reviewed. The sterically crowded triarylphosphines conjugated with various π-electron systems were synthesized from the common synthetic intermediate, (bromoaryl)phosphine, by conventional manner. The sterically crowded triarylphosphines conjugated with the electron acceptors exhibit visible absorption and fluorescence with large Stokes shift. Large solvent effect, redshift in polar solvent, and good correlation with the difference of the oxidation potential of the phosphine moiety and the reduction potential of the acceptor moiety suggest polar excited state resulting from HOMO-LUMO transition.     

Radiation-Induced Polymerization and Pressure-Volume Behavior of Acrylonitrile at High Pressure

Radiation-induced polymerization and pressure-volume (P-V) measurements of acrylonitrile (AN) were studied up to 8000 kg/cm² in the temperature range of 6–72°C. P-V isotherms of AN have several small breaks, A phase diagram of AN was obtained from the breaking pressures and temperatures. Liquid phases were named L_I, L_II, and L_III, from low to high pressure. The polymerization behavior and volume contraction on polymerization changed in L_I, L_II, and L_III. The difference in entropy between original and activated states decreased with increasing pressure at the same phase, but increased with phase change in L_I to L_II and L_II to L_III. It was concluded from these results and from IR data on PAN that molecular packing of AN in liquid changed in L_I, L_II, and L_III. In L_II and L_III, AN molecules aligned in a less suitable geometry for polymerization than in L_I.