New synthetic methods for 4-amino-2(5H)-furanones

Two new efficient methods are disclosed for the synthesis of the title compounds: (1) base-promoted ring closure of 2-acyloxy alkanenitrile and (2) acid-mediated lactonization of t-butyl 4-alkoxy-3-amino-2-alkenoates.     

Time-resolved investigation of the de-excitation of xenon excimer by SF6 and N2 excited with synchrotron radiation

An attempt has been made 'o measure the rate constant for the de-excitation of a state-specified excimer using the pulse character of synchrotron radiation. The rate constants have been obtained for de-excitation of a vibrationally relaxed excimer Xe₂^*(O_u⁺; low v) by SF₆ and N₂ as 9 × 10^?10 and 7 × 10^?12 cm³ molecule^?1 s^?1 respectively.     

Synthesis of aromatic polyamide-imides from N,N′-bis(trimethylsilyl)-substituted aromatic diamines and 4-chloroformylphthalic anhydride

The polymerization of N,N′-bis(trimethylsilyl)-substituted aromatic diamines with 4-chloroformylphthalic anhydride in various solvents at a temperature range between 10 and 70°C afforded polyamide-amic acid trimethylsilyl esters having inherent viscosities of 0.8–1.4 dL/g. Transparent and flexible films of the silylated precursor polymers were obtained by casting directly from the polymer solutions. Desilylation of the silylated polymers with methanol resulted in the formation of the corresponding polyamide-amic acids. Subsequent thermal imidization of the silylated precursor polymers with the elimination of trimethylsilanol afforded yellow, transparent, and tough films of the aromatic polyamide-imides. The thermal conversion of the silylated precursor polymer to polyamide-imide proceeded almost as rapidly as that of the corresponding polyamide-amic acid prepared by a conventional method from the parent aromatic diamine and 4-chloroformylphthalic anhydride.     

Model studies and a new melt polycondensation route to poly-bisphenol a–iso/terephthalate (polyarylate)

Alternate syntheses of polyarylate from dimethyl iso/terephthalate (DMI/DMT) and bisphenol-A (BPA) or bisphenol-A diacetate (BPAOAc) were investigated using a variety of catalysts. The model exchange of DMT with 4-t-butylphenol with loss of methanol proceeded moderately rapidly at rather low temperature (170°C) to produce to mono- and di-t-butylphenyl terephthalates. Dibutyltin oxide is the preferred catalyst. Alkali metal phenoxides are almost as effective but were less soluble. The model reaction of DMT with 4-tert-butylphenyl acetate involving loss of methyl acetate gave comparable results using dibutyltin oxide as catalyst. Based on these model results, polycondensations of DMI/DMT with BPAOAc under optimal conditions, gave polyarylate having an inherent viscosity 0.34 dL g^?1 in quantitative yield and light brown color. Polycondensation with BPA was unsatisfactory in terms of yield, molecular weight, and color.     

Application of schlieren optics to real-time monitoring of protein electrophoresis in crosslinker-free linear polyacrylamide solution

Molecular sieving effect of crosslinker-free linear polyacrylamide solutions could be visualized in a real-time mode using schlieren optics for electrophoresis of proteins. Since linear polymer solutions are going to find application in capillary electrophoresis (Zhu, M., et al., J. Chromatogr. 1989, 480, 311-319), the above approach may be useful for obtaining basic data of electrophoresis of proteins and nucleic acids in such media under conditions free from the predominant wall effect pertinent to the use of a capillary.     

Photochemical (2 + 2) cycloaddition of and thermal decomposition to n-methylacridone and acetone: chemiluminescence as a probe of possible formation of 1,2-dioxetanes

Irradiation of N-methylacridone (NMA) in an acetone solution at ?78°C in the argon atmosphere afforded light emission (φ_CL: 10^?6 - 10^?8 einstein/mol) upon warming-up to room temperature. The final products were NMA acetone exclusively.     

Extraction with 8-quinolinol and mixed anionic additives using ultrasonic irradiation for the catalytic determination of vanadium in freshwaters

Solvent extraction with 8-quinolinol (QN) has been markedly improved by the combined application of ultrasonic irradiation and mixed additives and used for the catalytic determination of vanadium with chlorpromazine in the presence of tartrate. Vanadium in an acidified sample up to 200 ml is extracted twice at pH 3.9–4.3 into two 10-ml portions of CHCl₃ with 0.14 M QN, and then back-extracted at pH 11 into 10 ml of 0.01 M NaOH solution. Each extraction time is 10 min. In the back-extraction, recovery of vanadium over 95% was performed by the addition of a mixed solution of KBr, NaBrO₃ and HNO₃ to the sample and the application of ultrasonic irradiation for 10 (or 5) min. On the other hand, a conventional mechanical shaking without the mixed solution required 60 min for 91% recovery. The proposed method was able to separate vanadium from Ca(II), Mg(II), Al(III), Fe(III), Cu(II), Cr(VI) and NO⁻₂, and has been successfully applied to the determination of vanadium in river and tap waters. The detection limit of vanadium was about 0.03 μg l⁻¹.     

The Effect of Ge, Ni, and Fe Doping on the Ga Activity in the CoGa B2 Phase

Gallium activity in the B2 (CsCl-type) phase of ternary Co–Ga–X (X = Ge, Ni, and Fe) alloys was measured by the EMF method with a stabilized zirconia solid electrolyte. The temperature range was 1050–1250 K and the concentrations of the added elements were 2–6 at-% Ge and Ni, and 1–3 at-% Fe. The reference electrodes were Fe,Fe_xO or Ga,Ga₂O₃. The effect on the activity of gallium in the B2 phase with the addition of other elements was found to be the largest with Ge and the smallest in the case of Ni.     

Inclusion complex formation between alpha-cyclodextrin and biodegradable aliphatic polyesters

Inclusion complexes (ICs) between alpha-cyclodextrin (alpha-CD) and three kinds of biodegradable aliphatic polyesters with different sequence lengths of the monomeric repeating units poly(3-hydroxypropionate) [P(3HP)], poly(4-hydroxybutyrate) [P(4HB)] and poly(epsilon-caprolactone)(PCL) were prepared by mixing a solution of alpha-CD with that of the polymer, followed by stirring. The ICs were obtained as insoluble precipitates and characterized by FT-IR, WAXD and DSC. All measurements showed that the polymer chains of all three kinds of polyester were included into the alpha-CD cavity and formed ICs with different stoichiometries. WAXD patterns and thermal analysis indicated that these ICs possessed a channel structure and the crystallization of the polyester chains was suppressed upon inclusion into the alpha-CD cavity.