Precipitation behavior of 1,1,Di-(p-hydroxyphenyl)-cyclohexane clathrate crystals from acetone solutions containingd-limonene

The precipitation behavior of 1,1-di(p-hydroxyphenyl)cyclohexane (DHC) from acetone solutions containing d-Limonene (1-methyl-4(I-methylethenyl)cyclohexene) was studied. From the pure acetone solution or the solutions containing a small amount of d-Limonene crystals (B) precipitated, which clathrate only acetone with a guest/host (G/H) molar ratio of 1.0. However, when thed-Limonene concentration is increased to more than ca. 2 mol/L, crystals (A) precipitated which had a different habit from the B crystals. In the A crystalsd-Limonene is clathrated together with a large amount of acetone and the G/H value ofd-Limonene increases with the concentration in the solution up to the maximum value of 0.2. As the diffraction patterns of the A and B crystals are similar, it is assumed that a part of the acetone molecules in the B crystals are replaced byd-Limonene molecules. The acetone in the A crystals escapes rapidly, but thed-Limonene remains for a long time. This may indicate that the large molecule ofd-Limonene cannot diffuse rapidly within the host lattice owing to three-dimensional hindrance. It was clear that the solubility of the A crystals is higher than that of the B crystals and the transformation from the'metastable A to the stable B crystals proceeds during the crystallization of A crystals.     

3,3′‐Dihydr­oxy‐5,5,5′,5′‐tetra­methyl‐2,2′‐thio­dicyclo­hex‐2‐en‐1‐one

Mol­ecules of the title compound, C₁₆H₂₂O₄S, have twofold crystallographic symmetry and are stabilized by strong intra­molecular O—H⋯O hydrogen bonds and very weak inter­molecular C—H⋯O hydrogen bonds, forming layers normal to the c axis. The mol­ecular structure is compared with those of the Se‐ and CH₂‐bridged analogues.     

Isotactic poly(acrylonitrile) via ultraviolet irradiation of acrylonitrile-urea canal complex

Isotactic poly(acrylonitrile) (PAN) has been prepared by means of a conventional ultraviolet (UV) irradiation apparatus without γ-ray sources; an acrylonitrile-urea canal complex was directly formed at the surface of the UV (Hg) emission tube at low temperatures (～ ?78°C). When the complex was UV-irradiated at this temperature, a stereoregular polymer was formed in the canal. The ¹³C-NMR analyses indicate that (1) these PAN are rich in isotactic configuration, (2) the extent of the isotactic triad is in the range of 56?71%, and (3) the penultimate unit effect, 4 (mm) (rr)/(mr)², is linearly correlated with the ultimate unit effect, (mm)/(rr). From the plots of log{4(mm)(rr)/(mr)²} vs log{(mm)/(rr)}, the anomaly in the polymerization of AN is discussed. The molecular characteristics of the UV canal PAN such as molecular weight, etc., were briefly noted. © 1995 John Wiley & Sons, Inc.     

An Unusual Mixed-guest Inclusion Compound. Crystal Structures of the Host Compound Hexakis(3-hydroxy-3,3-diphenylprop-2-ynyl)benzene, and its Inclusion Compound with Acetonitrile and Benzene

The crystal structures of the -phase of hexakis(3-hydroxy-3,3-diphenylprop-2-ynyl)benzene (1), and its inclusion compound with acetonitrile and benzene (2) have been determined by single crystal diffraction. 2 was further characterised by nuclear magnetic resonance spectroscopy, and thermal analysis. The inclusion of benzene by this host appears to depend on the presence of acetonitrile.     

Synthesis and DNA strand breakage activity of some 1,4-diazepines

Reactions of 1,3-propanediamine with alpha-dicarbonyl compounds (1a-e) were examined and various condensed heterocyclic compounds such as 1,4-diazepines (2) and 3-pyrimidine derivatives (3) were obtained. Some of 1,4-diazepines (2) showed DNA strand breakage activity.     

Hydrogen-bonding dynamics of free flavins in benzene and FAD in electron-transferring flavoprotein upon excitation

The dynamic natures of two hydrogen-bonding model systems, riboflavin tetrabutylate (RFTB)-trichloroacetic acid (TCA) and RFTB-phenol in benzene, and of electron-transferring flavoprotein (ETF) from pig kidney upon excitation of flavins was investigated by means of steady state and time-resolved fluorescence spectroscopy. In both model systems fluorescence intensities of RFTB decreased as TCA or phenol was added. The spectral characteristics of ETF under steady state excitation were quite similar to those of the RFTB-TCA system, but not to those of the RFTB-phenol system. The observed fluorescence decay curves of ETF fit well with the calculated decay curves with two lifetime components, as in the model systems. Averaged lifetime was 0.9 ns. The time-resolved fluorescence spectrum of ETF shifted toward longer wavelength with time after pulsed excitation, which was also observed in the RFTB-TCA system. In the RFTB-phenol system the emission spectrum did not shift at all with time. These results reveal that the dynamic nature of ETF can be ascribed to aliphatic hydrogen-bonding(s) of the isoalloxazine ring with surrounding amino acid(s). From the fluorescence characteristics of ETF in comparison with the model systems, human ETF and other flavoproteins, it was suggested that ETF from pig kidney does not contain Tyr-16 in the beta subunit, unlike human ETF.     

The effect of crystalline phase on the fluorescence characteristics of solid cyclohexane and bicyclohexyl

Emission from cyclohexane and bicyclohexyl solids has been found to critically depend on their crystalline structure. The emission spectrum of cyclohexane suddenly blue-shifts 2900 cm^?1 on cooling below its solid—solid phase transition temperature (?87.1°C). The bicyclohexyl emission intensity sharply decreases on freezing to solid and then again sharply recovers at a heretofore unreported phase transition temperature (≈ 0°C) with the spectrum 2500 cm^?1 blue-shifted from that of the liquid. The results are discussed utilizing the partial Rydberg nature of the excited cycloalkane states.     

Stereospecific polymerization of methacrylonitrile. I. Characterization of crystalline polymethacrylonitrile

Methacrylonitrile (MAN) was polymerized with diethylmagnesium. Acetone-insoluble portions of the polymers are found to be crystalline. Highly crystalline portions can be isolated by further extraction of the acetone-insoluble parts with dimethylformamide (DMF). A film of DMF-insoluble fraction can be oriented uniaxially by hot-press rolling. The crystalline PMAN is insoluble in the usual solvents for amorphous PMAN because of their crystallinity and is easily soluble in CF₃COOH or Cl₂CHCOOH. The viscosity–molecular weight relationship was determined in Cl₂CHCOOH at 30°C. as [η] = 3.24 × 10^?3M^0.520. We found several crystalline bands in the infrared spectra, for example, at 1192 and 885 cm.^?1. Formation of the carbonyl group in the polymer is discussed, and it is concluded that it may be formed by the hydrolysis of conjugated cyclic imine or hydrolysis of the nitrile group in the polymer to acid amide.