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41.
[reaction: see text]. The sum of the rate constants for solvolysis and 18O-scrambling of 4-MeC6H4(13)CH(Me)18OC(O)C6F5 in 50/50 (v/v) trifluoroethanol/water, k(solv) + k(iso) = 1.22 x 10(-5) s(-1), is larger than k(solv) = 1.06 x 10(-5) s(-1) for solvolysis of the unlabeled ester. This shows that the ion pair intermediate undergoes significant internal return. The data give k(-1) = 7 x 10(9) s(-1) for internal return by unimolecular collapse of the ion pair, which is significantly larger than k(Nu) = 5 x 10(8) M(-1) x s(-1) for bimolecular nucleophilic addition of carboxylate anions to 4-MeC6H4CH(Me)+. 相似文献
42.
Summary The ion exchange selectivity of trivalent metal ions has been determined on titanium antimonate cation exchanger prepared by coprecipitation of antimony to titanium at different mole ratios. The selectivity sequence Al3+<Cr3+<Ga3+<In3+<Fe3+ was found for trivalent metal ions at an initial concentration of 10–4 mol dm–3 in nitric acid media. A high separation factor Ga/Al = KdGa/KdAl, 4.8×103, was observed for the Ga3+–Al3+ pair on titanium antimonate with an antimony to titanium ratio of 0.34. The effective separation of Ga3+ and In3+ from Al3+ was achieved using a 3 cm×0.5 cm i.d. column containing titanium antimonate with an antimony to titanium ratio of 0.34. 相似文献
43.
Norio Miyoshi Kiyoaki Hara Issei Yokoyama Giiti Tomita Masaru Fukuda 《Photochemistry and photobiology》1988,47(5):685-688
Abstract— The absorption and fluorescence spectra, and the fluorescence lifetime of acridine orange (AO) were measured in a wide range of the sodium dodecyl sulfate (SDS) concentration below and above the critical micelle concentration (cmc). The fluorescence consisted of two components with different lifetimes; short (<3 ns) and long (>3 ns). The short and long lifetime components are attributed to the AO monomer and dimer associated with detergent, respectively. The lifetime of the dimer increased with increasing the SDS concentration just below the cmc. It decreased suddenly to a constant value just above the cmc. The lifetime of the monomer showed only a slight increase in the concentration range of SDS employed. 相似文献
44.
Y. Sakuma Y. Ogata N. Tsuji H. Yamanishi T. Iida 《Journal of Radioanalytical and Nuclear Chemistry》2003,255(2):325-327
Liquid scintillation counting is the most popular method for tritium measurement, however, it takes much time and a lot of doing to distill off the impurities before mixing the sample water and liquid scintillation cocktail. We have investigated the possibility of an alternative method to the distillation. We have found out that the filtration can be an alternative to distillation for the environmental water samples before electrolytic enrichment. 相似文献
45.
Tsuji M 《The Journal of organic chemistry》2003,68(25):9589-9597
We have synthesized all three possible isomers of C-hydroxycarborane from the corresponding amines via diazotization. The O-protonated C-hydroxycarboranes were characterized using the NMR spectrum measurements. Attempts at generating of carboranyl carbocations were carried out by the solvolyses of C-tosylates and C-triflates, as well as by treatment with superacids. Anchimeric assistance of both homoconjugative and hyperconjugative substituents was also investigated, as demonstrated by a successful strategy devised for the solvolytic generation of a phenyl cation. However, we have not been able to chemically provide any evidence of carboranyl carbocations, although the carboranyl carbocation may be an intermediate in the decomposition of the C-carboranediazonium ion. 相似文献
46.
Yasuo Kameda Motoya Sasaki Masahiro Yaegashi Kosuke Tsuji Shingo Oomori Shuji Hino Takeshi Usuki 《Journal of solution chemistry》2004,33(6-7):733-745
Time-of-Flight (TOF) neutron diffraction measurements have been carried out on aqueous 8 mol% sodium acetate solutions in D2O. Scattering cross sections that were observed for sample solutions involving 12C/13C and H/D isotopically substituted acetate ions were used to derive the first-order difference functions, ΔH(Q) and ΔC(Q), and corresponding distribution functions, G H(r;r) and G C(r;r), which describe the environmental structure around the methyl and the carboxyl groups within the acetate ion, respectively. Structural parameters concerning the first hydration shell of the carboxyl group within the acetate ion were obtained through the least squares fit to the observed intermolecular difference function, ΔC inter(Q). The nearest neighbor C O...D W1 (CO: carboxyl carbon atom, DW1: water deuterium atom) distance, r(C O...D W1 ), and the angle, ∠ C O ...D W1 -O W (O W : water oxygen atom), were determined to be 2.63(1) Å and 120(1)°, respectively. The coordination number, n(C O ...D W1 ), was obtained to be 4.0(1). These results are consistent with the hydration structure in which water molecules in the first hydration shell of the carboxyl group are hydrogen-bonded with oxygen atoms of the carboxyl group. 相似文献
47.
Momchilova S Tsuji K Itabashi Y Nikolova-Damyanova B Kuksis A 《Journal of separation science》2004,27(12):1033-1036
The ability of reversed-phase high-performance liquid chromatography (RP-HPLC) to separate some positionally isomeric disaturated and monounsaturated triacylglycerols (TAGs) as intact species is demonstrated for the first time. Mobile phases of acetonitrile modified with methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, acetone, or dichloromethane were tested for the separation of POP-PPO, PLP-PPL, PEP-PPE, and PDP-PPD (P-palmitic, O-oleic, L-linoleic, E-eicosapentaenoic, D-docosahexaenoic acid residue) on a single RP-HPLC column. The resolution improved with increasing number of double bonds in the acyl residues. While POP and PPO were only partially resolved, PDP and PPD were fully separated with all tested mobile phases, except those containing methanol. Also separated were the four TAGs having the same equivalent carbon number (ECN = 42), PEP, PPE, PDP, and PPD, on a single RP-HPLC column with mobile phase acetonitrile-2-propanol (70:30, v/v) at 0.8 mL/min. In all cases the isomer with the unsaturated acyl residue in either 1- or 3-position was retained more strongly than the respective 2-isomer. 相似文献
48.
Ishizaka T Miyanaga Y Mukai J Asaka K Nakai Y Tsuji E Uchida T 《Chemical & pharmaceutical bulletin》2004,52(8):943-948
The purpose of this study was to evaluate the bitterness of 18 different antibiotic and antiviral drug formulations, widely used to treat infectious diseases in children and infants, in human gustatory sensation tests and using an artificial taste sensor. Seven of the formulations were found to have a bitterness intensity exceeding 1.0 in gustatory sensation tests (evaluated against quinine as a standard) and were therefore assumed to have an unpleasant taste to children. The bitterness intensity scores of the medicines were examined using suspensions in water or an acidic sports drink. In the case of three macrolide antibiotic formulations containing erythromycin (ERYTHROCIN dry syrup), clarithromycin (CLARITH dry syrup for pediatric), and azithromycin (ZITHROMAC fine granules for pediatric use), the bitterness intensities of suspensions in acidic sports drinks were dramatically enhanced compared with the corresponding scores of suspensions in water. This enhancement could be predicted using the taste sensor. On the other hand, a reduction of bitterness intensity was observed for an acidic sports drink suspension of an amantadine product (SYMMETREL fine granules) compared with an aqueous suspension. This reduction in bitterness could also be predicted using the taste sensor output value. Thus, the taste sensor could predict whether or not suspension in an acidic sports drink would enhance or reduce the bitterness intensity of pediatric drug formulations, compared with suspensions in water. 相似文献
49.
50.
Homogeneous palladium catalyst suppressing Pd black formation in air oxidation of alcohols 总被引:1,自引:0,他引:1
Iwasawa T Tokunaga M Obora Y Tsuji Y 《Journal of the American Chemical Society》2004,126(21):6554-6555
In homogeneous catalyst systems, there is the persistent problem that metal aggregation and precipitation cause catalyst decomposition and considerable loss of catalytic activity. Pd black formation is a typical example. Pd catalysts are known to easily aggregate and form Pd black, although they realize a wide variety of useful reactions in organic synthesis. In order to overcome this intrinsic problem of homogeneous Pd catalysis, we explored a new class of Pd catalyst by adopting aerobic oxidation of alcohols as a probe reaction. Herein we report a new catalyst system that suppresses the Pd black formation even under air and with a high substrate to catalyst molar ratio (S/C: more than 1000) in oxidation of alcohols. The novel pyridine derivatives having a 2,3,4,5-tetraphenylphenyl substituent and its higher dendritic unit at the 3-position of the pyridine ring were found to be excellent ligands with Pd(OAc)2 in the palladium-catalyzed air (balloon) oxidation of alcohols in toluene at 80 degrees C. Comparison with structurally related pyridine ligands revealed that introduction of the 2,3,4,5-tetraphenylphenyl substituent at the 3-position of pyridine ring effectively suppresses the Pd black formation, maintaining the catalytic activity for a long time to give aldehydes or ketones as products in high yields. 相似文献