Effect of fluorine substituents on the properties of nylon copolymers

Nylon 610/65F and nylon 610/65 copolymers were prepared by melt polycondensation from the diethylester of sebacic acid (10) and hexafluoroglutaric acid (5F) or glutaric acid (5) with hexamethylene diamine (6). Reduced specific viscosities of nylon 610/65F were lower than those of nylon 610/65. The crystallinity measured by WAXS and the melting point measured by DTA were depressed by the copolymerization. The melting point depression of nylon 610/65F was much larger than that of nylon 610/65. The thermal decomposition temperature measured by TG was also depressed significantly for nylon 610/65F. The residue at 600°C was increased by the fluorine substitution. The copolymers with higher fluorine content became flame retardant. The solubility was appreciably affected by the fluorine substitution. The contact angle for nylon 610/65F varied in a complicated manner with increasing 65F content and tended to be higher than the corresponding nylon 610/65.     

由从头算Hartree-Fock MO法对叔丁基过氧化氢与N,N-二甲苯胺反应机理的探讨

本文由从头算Hartree-Fock(STO-3G)MO法来探讨叔丁基过氧化氢(BHP)与N,N-二甲苯胺(DMA)的反应机理。该反应是由如下三种反应组成的。(1)DMA的N攻击BHP的O~1而形成N-氧化物(方式1);(2)生成氢键复合物(方式2);(3)由DMA的N攻击BHP的O~2而生成自由基(方式3)。上列三种的微挠能量经计算结果分别为0.2276、0.1687、0.2056 eV。因此,我们可得此三种反应机理的结论。     

Microbial conversion of 4-oxoisophorone by thermomonospora curvata using an air-bubbling hollow fiber reactor

Microbial conversion of 4-oxoisophorone (OIP) by thermophilic bacteriumThermomonospora curvata was attempted in a continuous process. The correlation between cell growth and microbial conversion was first examined in a batch culture. The results indicated that this microbial conversion was strongly dependent upon cell growth. In a continuous microbial conversion of OIP using a continuous stirred tank reactor, the cell density in the reactor seemed to be the limiting factor in the OIP conversion. Therefore, we developed an air-bubbling hollow fiber reactor to achieve a high density culture. By using this bioreactor, more than 3.3 times higher productivity was achieved. In addition, during the process, only a slight cell contamination to the product was observed. Therefore, this bioreactor is suitable for the continuous microbial conversion, considering further downstream processes and high productivity.     

Activation of silylphosphines by diethyl azodicarboxylate: novel silylation of alcohols

A novel activation mode of silylphosphines and an application of that to silylation of alcohols were described. Silylphosphines were found to be instantly activated by means of DEAD and PPTS to form reactive silyl cation equivalents. By using the activated species, silylation of alcohols successfully proceeded under mild acidic condition.     

Application of the TORO technique of 1H NMR to the structural analysis of cyclic peptide isomers having a slightly distorted symmetry from C2

The extended TORO technique was applied to the structural analysis of endo-D-Tyr-gramicidin S, cyclo(-Val-Orn-Leu-D-Phe-D-Tyr-Pro-Val-Orn-Leu-D-Phe-Pro-), which has a slightly distorted symmetry from C2, by the insertion of D-Tyr and equivalent alpha-proton chemical shifts in the 1H NMR spectrum. All NMR signals of the two dominant isomers of this antibiotic with trans-trans prolines were determined by using the extended TORO technique with TOCSY and ROESY spectra. This technique is generally applicable for distinguishing overlapped signals of alpha- and amide protons from the main chains of peptides.     

Synthesis of symmetric HIJ-ring model of ciguatoxin

A tricyclic model ether compound comprising 6/8/6 ether rings was synthesized via a new route including conjugate addition to form a symmetric eight-membered ether-ketone with syn/trans stereochemistry in selective manner. The corresponding vinyl triflate of this ketone was allowed to convert to the vinyl methyl derivative via cross-coupling reaction. This endo-olefinic tetrahydro-2H-oxocin was selectively reduced to afford α-methyl product. The corresponding exo-olefinic oxocane derivative, on the other hand, provided the β-methyl isomer as the major diastereoisomer (2/1). Our previous report on the synthesis of this final product was revised due to some rearrangement and the mechanisms are discussed.     

Photosensitivity and photochemical reactions of poly(vinyl p-azidocinnamate)

The spectral sensitivity of poly(vinyl p-azidocinnamate)(PVACi) was discussed by comparison with poly(vinyl cinnamate)(PVCi) and poly(vinyl p-azidobenzoate). The photochemical reaction of PVACi was investigated with respect to the reactivity of two functional groups, namely, azido and cinnamoyl groups. It was found that cinnamoyl groups dimerized like PVCi and azido groups did not add to double bonds appreciably. The quantum yield of photolysis of azido groups was two times that of dimerization of cinnamoyl groups. A marked wavelength dependence of π–π^* and n–π^* absorption was observed in both the reactions of azido and cinnamoyl groups.     

Solvent extraction of microgram amounts of magnesium with 8-quinolinol and tetrabutyl-ammonium iodide followed by spectrophotometry with chlorophosphonazo-III

A rapid and sensitive solvent-extraction procedure for the separation of magnesium is reported. Microgram (0.1–10) amounts of magnesium are extracted with a chloroform solution of 8-quinolinol and tetrabutylammonium iodide in the presence of tartrate and phosphate. Magnesium is then back-extracted into an aqueous buffer solution (pH 7.3; tetrabutylammonium hydroxide—boric acid) and determined spectrophotometrically using chlorophosphonazo-III. Up to 500 mg of sulphate, phosphate or cyanide, 200 mg of chloride, 20 mg of aluminum, barium or silicate, and 2 mg of calcium can be tolerated.     

Peroxyoxalate chemiluminescence of N,N'-bistosyl-1H,4H-quinoxaline-2,3-dione and related compounds. Dependence on electronic nature of fluorophores

The title compound N,N'-bistosyl-1H,4H-quinoxaline-2,3-dione (TsQD) provides peroxyoxalate chemiluminescence (PO-CL) when reacted with hydrogen peroxide in the presence of fluorophores. The chemiluminescence (CL) efficiency of TsQD was superior to that of other related compounds such as bis(2,4,6-trichlorophenyl) oxalate (TCPO), a typical oxalate for the peroxyoxalate PO-CL, under an aqueous condition. Factors affecting the PO-CL efficiency are discussed from the viewpoint of the structures of the substrates and the electronic nature of the fluorophores. A linear correlation of the logarithmic values evaluated from the CL quantum yields with the oxidation potentials of the aromatic fluorophores supports the involvement of the chemically initiated electron exchange luminescence (CIEEL) mechanism in both TsQD- and TCPO-CL systems. Also, an excellent Hammett relationship was derived from the correlation between the sigma(+) values and the relative singlet excitation yields in TsQD-CL enhanced by a series of fluorescent para,para'-disubstituted distyrylbenzenes.