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51.
Taguchi Y Ohtani H Tsuge S Ishida Y Kimura K Yoshikawa T 《Journal of chromatography. A》2003,993(1-2):137-142
Highly sensitive and specific determination of trace amounts of a polymeric hindered amine light stabilizer (HALS) in polypropylene (PP) materials could be established by improving reactive thermal desorption-gas chromatography (RTD-GC) in the presence of an organic alkali, tetramethylammonium hydroxide. By using nitrogen-phosphorus detection, highly selective detection of the HALS-related components was attained. In addition, the use of a polar poly(ethylene glycol) separation column alleviated the adsorption of minor specific pyrolysis products. This modified RTD-GC method allowed the determination of the polymeric HALS (Mr 1900) in PP even for trace concentrations between 100 and 500 ppm, through observing selectively the characteristic products containing a tetramethylpiperidine moiety, which had been impossible to detect under the previous RTD-GC conditions using a non-polar separation column and conventional flame ionization detection. 相似文献
52.
Kubo M Takizawa T Wakai C Matubayasi N Nakahara M 《The Journal of chemical physics》2004,121(2):960-969
The site-selective H/D exchange reaction of phenol in sub- and supercritical water is studied without added catalysts. In subcritical water in equilibrium with steam at 210-240 degrees C, the H/D exchange proceeds both at the ortho and para sites in the phenyl ring, with no exchange observed at the meta site. The pseudo-first-order rate constants are of the order of 10(-4) s(-1); 50% larger for the ortho than for the para site. In supercritical water, the exchange is observed also at the meta site with the rate constant in the range of 10(-6)-10(-4) s(-1). As the bulk density decreases, the exchange slows down and the site selectivity toward the ortho is enhanced. The enhancement is due to the phenol-water interaction preference at the atomic resolution. The site selectivity toward the ortho is further enhanced when the reaction is carried out in benzene/water solution. Using such selectivity control and the reversible nature of the hydrothermal deuteration/protonation process, it is feasible to synthesize phenyl compounds that are deuterated at any topological combination of ortho, meta, and para sites. 相似文献
53.
Photocatalytic reactions occurring at semiconductor particles/solution interfaces can be applied to organic syntheses. In this review article, examples of photocatalytic syntheses of cyclic amino acids by suspended semiconductor particles, e.g., titanium(IV) oxide or cadmium(II) sulfide are introduced and interpreted. Different from the photocatalytic decomposition of pollutants under aerobic conditions, selective conversion of organic compounds can be driven by the photocatalytic reactions under deaerated conditions. 相似文献
54.
Masaru Yoneyama K. D. Athula Kuruppu Masa-Aki Kakimoto Yoshio Imai 《Journal of polymer science. Part A, Polymer chemistry》1988,26(11):2917-2922
Aromatic polyamides (aramids) having inherent viscosities of 0.5–1.10 dL/g were prepared by the direct polycondensation of 1,1,3-trimethyl-3-(4-carboxyphenyl)indane-5-carboxylic acid with various aromatic diamines using triphenyl phosphite and pyridine as the condensing agents. Copolyamides were also prepared by a similar procedure from a mixture of the phenylindane diacid, terephthalic acid, and p-phenylenediamine. Almost all of the aramids were soluble in a variety of solvents such as N-methyl-2-pyrrolidone, pyridine, and m-cresol, and afforded transparent and tough films by the solution casting. These aramids and copolyamides had glass transition temperatures in the range of 290–355°C, and started to lose weight at 340°C in air. 相似文献
55.
Du YZ Hiratsuka Y Taira S Eguchi M Uyeda TQ Yumoto N Kodaka M 《Chemical communications (Cambridge, England)》2005,(16):2080-2082
A new nano-biomachine has been created from microtubules (MTs) and hetero-bifunctional polymer particles bearing pyruvate kinase, which is propelled on glass surfaces coated with kinesin by use of self-supplying ATP. 相似文献
56.
An intensely sweet polyoxypregnane glycoside, telosmoside A15 (15), was isolated from an Asian Asclepiadaceae plant, Telosma procumbens, collected in Vietnam. This is the first time a sweet pregnane glycoside has been found, and its sweetness intensity is 1000 times greater than that of sucrose. From the same plant, 17 other new glycosides were isolated, having the same aglycone; they are named telosmosides A1-A14 (1-14) and A16-A18 (16-18). Some of these glycosides are also sweet, but others are tasteless or bitter. Chemical structures of the 18 glycosides were determined, and the structure-taste relationship was discussed. 相似文献
57.
Masaru Kojima 《Tetrahedron letters》2007,48(25):4431-4436
A new fluorous benzylidene acetal protecting group was regioselectively introduced into carbohydrates, deprotected under acidic conditions, and reused. Oligosaccharides were synthesized via regioselective conversion of the fluorous acetal group to the benzyl group by traditional reaction conditions. The fluorous compounds were easily separated from non-fluorous by-products by fluorous solid phase extraction. 相似文献
58.
Phototactic responses of newly hatched silkworm larvae to monochromatic lights and their mixtures were measured to determine wavelength-dependent properties. Each fluence rate-response curve for a monochromatic light was composed of a log-linearly increasing part, a plateau and a decreasing part. Curves were classified into two groups according to the slopes of the linear parts: responses to UV-blue light (364-482 nm) and responses to green-red light (513-681 nm). Different plateau values were found for both groups. The action spectrum had its maximum at 557 nm and showed another large value at about 364 nm, and its minimum was at 447 nm. When green-orange lights (540-577 nm) were added to 557 nm, the silkworms were attracted more by the mixed lights than by the 557 nm component light only. Mixed lights of UV (364 nm) and blue (447 nm) attracted the silkworms more than either component. The magnitude of the response decreased remarkably when green light was mixed with U V or blue light. We conclude that the silkworm possesses colour vision and responds differently to green-red lights (≥ 513 nm) from UV-blue lights (≲ 482 nm). 相似文献
59.
Smiles-type free radical rearrangements of arenesulfonates and arenesulfonamides are exploited for synthetic purposes. 4-Substituted benzenesulfonates cause Smiles-type rearrangement only when substituted by an electron withdrawing group. Therefore, ipso-attack by an alkyl radical on arenesulfonates takes place in an electrophilic manner. Arenesulfonamides rearrange only when the amide nitrogen is substituted by an alkoxycarbonyl group, due to the electron withdrawing nature of this group. Sulfonates and the N-ethoxycarbonylsulfonamide derivatives of naphthalene, quinoline, and thiophene cause more rearrangement and show synthetic utility. Aromatic amino acid analogues were synthesized by Smiles-type rearrangement with moderate yields. The radical Smiles-type rearrangement of sulfonate and sulfonamide derivatives can be a useful synthetic route when we understand the electronic character of these reactions. 相似文献
60.
3,4-Dhydro-6,7-dimethoxy-4-methyl-3-oxo-quinoxaline-2-carbonyl azide is a highly senstive fluorescence derivatization reagent for primary, secondary and tertiary alcohols for high-performance liquid chromatography. Reaction conditions are optimized with benzyl alcohol, n-hexanol, cyclohexanol and 2-methyl-2-butanol. The reagent reacts with the alcohols in benzene to produce the corresponding fluorescent carbamic acid esters, which can be separated on a reversed-phase column YMC Pack C8 with aqueous methanol as eluent. the detection limits for the alchols are 2–5 fmol per 10-μl njection. The reagent also reacts with hydroxysteroids with primary, secondary and/or tertiary alcoholic group(s) to form fluorescent derivatives. Hydroxycarboxylic acids and phenols do not give any chromatographic peaks. 相似文献