Statistical nonstationarity of the composition of styrene with methyl methacrylate in the cooligomer

It was found that the composition of cooligomer produced in the styrene(A)–methyl methacrylate(B)–CCl₄(S) system deviates from the statistical steady-state composition predicted from the Mayo-Lewis equation on the low molecular weight side when the molar ratio of [A]/[B] is large. When the molar ratio of [A]/[B] is small, however, it is not obvious whether or not this phenomenon is observed, because the cooligomer of low molecular weight cannot be obtained easily since the chain transfer constant of the poly(methyl methacrylate) radical to CCl₄ is very small in comparison, with that of the polystyryl radical. This behavior is shown to be attributable mainly to the preferential consumption of styrene monomer in the initiation step, based on the structure of the cooligomer, as inferred from the mechanism of the initiation, transfer, and termination, and the stochastic approach in which the cooligomerization process is regarded as a Markov process.     

The synthesis of benzofuroquinolines. IX. A benzofuroisoquinolinone and a benzofuroisocoumarin

Some procedures for a benzofuroisoquinolinone 1 were studied. Its O-analogous benzofuroisocoumarin 2 was synthesized from methyl salicylate with diethyl α-bromohomophthalate (9) . And, the benzofuroisoquinolinone 1 was obtained by treating 2 with ammonia gas in a sealed tube.     

Calibration study on the triton response of CR-39 track detector

Triton response of the CR-39 track detector has been studied at energy ranges below 2.7 MeV. Triton irradiation was made both on the top and the well polished side surface of the CR-39 sample sheets, using ⁶Li(n,t)⁴He reaction in a thermal neutron field. At large residual ranges more than 10 μm, fine results of etch rate ratio were obtained by analysing the growth curves of etch-pit radius on the top surface. But the response at near the track end-point could not be obtained well in this method, as a result of the missing track effect. Clearly resolved response at short residual ranges was attained by means of the shape analysis of the etch-pit profile observed on the side surface.     

Temperature factor of X-ray diffraction and diffuse scattering from helical polymer crystal

A theoretical treatment for the effect of thermal vibration on the X-ray scattering intensity for a helical polymer crystal is presented. The treatment involves assumptions that (1) the unit cell of the crystal contains only one polymer chain and (2) fluctuations of the atomic positions are small. The temperature factor of the intensity of Bragg reflections is expressed in terms of mean squares of fluctuations of helical parameters. The diffuse scattering is also considered in a special case.     

Chemistry of organosilicon compounds : CX. An electron spin resonance study on the silyl- and germyl- substituted methyl radicals. Hyperfine coupling constants of β-MH [M = Si,Ge) protons

ESR spectra of five metal-substituted methyl radicals of the type HR¹R²M-CR³R⁴ are recorded and analyzed. The magnitudes of a(β-SiH) were in a range of 14-15G, while a(β-GeH) of ·CH₂GeMe₂H was 10.20G. These coupling constants were markedly temperature dependent, suggesting that the most stable conformation of these radicals at low temperature is one in which the β-MH bond eclipses the $\text{p}$ orbital on the metal radical site.     

Infrared spectra of thiourea adducts occluding monobromocyclohexane or mixtures of monochloro-cyclohexane and monobromocyclohexane

Infrared spectra of a thiourea adduct of monobromocyclohexane were measured in the region 4000 cm^?1 to 30 cm^?1. The axial conformer was found to be predominant in the host lattice. Infrared spectra of thiourea adducts of mixtures of monochlorocyclohexane and monobromocyclohexane were also measured and the spectra interpreted.     

High performance liquid chromatographic determination of bound sulfide and sulfite and thiosulfate at their low levels in human serum by pre-column fluorescence derivatization with monobromobimane.

A sensitive and specific high performance liquid chromatographic method for the determination of sulfide, sulfite, and thiosulfate was established. Inorganic sulfur anions were converted into fluorescent derivatives with monobromobimane. The derivatives were separated on a coupled column chromatography with a reversed-phase octadecyl silica column connected with a weakly basic anion exchanger column by isocratic elution with acetic acid solution (pH 3)-acetonitrile (13:3, v/v) containing 25 mM NaClO4. The method was applied to the determination of bound sulfide and sulfite and thiosulfate in normal human serum. Thiosulfate could be determined directly by use of an ultrafiltered sample. For the determination of bound sulfide and sulfite, the pretreatment step with continuous flow gas dialysis was effective for the sample after releasing sulfide and sulfite by reduction with dithiothreitol. The limits of quantification by the present method were 0.05 microM for thiosulfate, 0.5 microM for bound sulfide, and 0.2 microM for bound sulfite.     

Cyclic hemiacetal and acyclic chain — the two forms of serricornin

The actual structures of the four stereoisomers of serricornin were examined by the X-ray analysis and high-field pmr spectroscopy. Each of the stereoisomers assumes either or both of two forms, cyclic hemiacetal and acyclic chain, in solution.     

Determination of semivolatile organic compounds in environmental samples by gas chromatography/mass spectrometry after extraction by cyclic steam distillation

A method was developed for the multiple determination of semivolatile organic compounds found in groundwater, river water, seawater, sediment, and soil. Forty standard compounds were determined: n-alkenes, cycloalkanes, aromatic hydrocarbons, and polycyclic aromatic hydrocarbons. The compounds were isolated from water and soil samples by using an essential oil distillator (cyclic steam distillator) with hexane as a solvent. The extract was cleaned by using a silica gel cartridge with an acetone-hexane solution. The compounds were determined by using a gas chromatograph/mass spectrometer with 12 stable isotope-labeled compounds (surrogate compounds). The efficiencies of recoveries from water samples were 80.0-106% for groundwater, 80.1-106% for river water, and 81.2-103% for seawater. The relative standard deviation (RSD) values were 2.05-16.0% for groundwater, 3.22-16.6% for river water, and 4.45-16.0% for seawater. The efficiencies of recoveries from sediment and soil were 71.5-96.4% and 70.1-99.8%, respectively. RSD values ranged from 2.27 to 16.0% for sediment and from 2.12 to 15.1% for soil. Adjustment of recovery efficiencies of standard compounds by using surrogate compounds gave more accurate values. The present study proved that an essential oil distillator provides satisfactory results for multiple determinations of the semivolatile compounds in environmental waters, sediment, and soil.