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61.
Jacques E. Desnoyers Gérald Perron Sylvain Léger Byron Y. Okamoto Terrence H. Lilley Robert H. Wood 《Journal of solution chemistry》1978,7(3):165-178
The freezing-point depression of the ternary systems tetraalkylammonium bromides-t-butanol-water for the first five homologs of R4NBr was measured. In the case of Bu4NBr, the effect of size of the alcohol (methahol ton-butanol) was also investigated. From the corresponding freezing-point data for the binary systems the apparent salting constants
were calculated. The true salting constantsk
s were obtained by extrapolation to infinite dilution. These are all very close to zero at the freezing temperature. From the
corresponding thermochemical data the temperature dependence ofk
s was calculated, and above 5°C all the R4NBr salts int-butanol; the salting-in increases with temperature and with the size of the hydrophobic cations. The scaled-particle theory
is at present the only one which can account semiquantitatively for the temperature dependence of the salting-in effect.
On leave of absence from Chemistry Department, The University, Sheffield S3 7HF, England
To whom correspondence should be addressed. 相似文献
62.
Treatment of 3,4-alkadienyl carbonates 2a-i with a low-valent titanium reagent diisopropoxy(eta(2)-propene)titanium (1), readily generated by the reaction of Ti(O-i-Pr)(4) with 2 i-PrMgCl, resulted in an intramolecular nucleophilic acyl substitution (INAS) reaction to afford vinyltitanium compounds 3 which, in turn, reacted with H(3)O(+), D(2)O, or iodine to give alpha-substituted beta,gamma-unsaturated esters 4 in good to excellent yields. The olefin moiety of the hydrolysis product 4 has (Z)-geometry mainly except for 4h. Starting from chiral 2f or 2g, the reaction proceeded stereospecifically to give optically active alpha-substituted beta,gamma-unsaturated ester 4f or 4g having (Z)-olefin geometry exclusively. 相似文献
63.
Simple syntheses of syncarpurea (1) from syncarpic acid and the amino acids ornithine or citrulline are presented. 相似文献
64.
65.
Yoshio Okamoto Motoyuki Toki Heimei Yuki 《Journal of polymer science. Part A, Polymer chemistry》1979,17(11):3705-3712
S-Methyl thiomethacrylate (methyl thiolmethacrylate, MTMA) was polymerized with a variety of anionic initiators such as n-BuLi, octylpotassium, PhMgBr, and Et2AlNPh2 in toluene and THF. Stereoregularity of the polymer (PMTMA) was determined from the 1H-NMR spectrum of poly(methyl methacrylate), which had been derived from PMTMA, because the α-methyl resonance in the 1H-NMR spectrum of PMTMA was not satisfactorily solved owing to the overlap of pentad signals. The 13C-NMR spectrum of PMTMA also showed the splitting due to pentad sequences. Stereoregularity of PMTMA was always low compared with that of poly(methyl methacrylate), which was prepared under the same reaction conditions. MTMA was much more reactive than methyl methacrylate and methacrylonitrile in the copolymerization with n-BuLi in toluene and in THF at ?78°C. The lower stereoregulation of the polymerization of MTMA and the higher reactivity of MTMA were mainly ascribed to the higher resonance effect of MTMA. 相似文献
66.
Yoshihisa Kurasawa Tomoyoshi Hosaka Kazue Ikeda Yuko Matsumoto Aiko Ishikura Atsushi Takada Ho Sik Kim Yoshihisa Okamoto 《Journal of heterocyclic chemistry》1994,31(2):527-533
The 3-(arylhydrazono)methyl-2-oxo-1,2-dihydroquinoxalines 9–11 were synthesized by the reaction of the quinoxalines 6–8 with various p-substituted benzenediazonium salts. Compounds 9–11 showed the tautomeric equilibria between the hydrazone imine A and diazenyl enamine B forms in dimethyl sulfoxide media. The substituent effect on the tautomer ratios of A to B was studied by the nmr spectroscopy to clarify that the presence of the ester group R2 on the hydrazone carbon and electron-donating p-substituent R1 on the side chain benzene ring exhibited a tendency to increase the ratios of the tautomer A . 相似文献
67.
68.
A rhodium-catalyzed isomerization of alpha-arylpropargyl alcohols to indanones has been developed under mild conditions. Considering the ease of preparation of these propargyl alcohols (terminal alkynes + aromatic aldehydes), this method provides a new way of constructing indanones with high efficiency. By the mechanistic investigations using deuterium-labeled substrates, it has also been demonstrated that the reaction goes through an unexpected cascade, with a 1,4-hydrogen shift being the turnover-limiting step of the catalytic cycle. 相似文献
69.
Akiko Tsuhako Jing-Qian He Mariko Mihara Naoko Saino Sentaro Okamoto 《Tetrahedron letters》2007,48(52):9120-9123
Ketones and aldehydes were effectively reduced to the corresponding alcohols (or their silyl ethers) by the reaction with CaH2 and R3SiCl in the presence of a catalytic amount of ZnCl2. In the absence of the carbonyl substrate, the reagent reduced R3SiCl to the corresponding hydrosilane under mild reaction conditions. 相似文献
70.
Isothermal
titration microcalorimetry has been applied to investigate the compatibility
testing of risperidone oral solution with soft-drinks and the interaction
with tea tannin such as (–)-epigallocatechin, (–)-epicatechin,
theaflavin and their gallates. In aqueous solution, risperidone was exothermically
bound to tea tannin with binding affinity (103–104
M–1), small enthalpy and entropy changes
reflecting van der Waal’s interaction to form an insoluble complex at
1:1 molar ratio. The heat effect of risperidone titrated into soft-drinks
containing tannin was exothermic and proportional to the quantity of the complex.
While, no significant heat effect was found for risperidone titrated into
a pet-bottled water and an infusion of parched barley without tea tannin.
These results were agreed with stability testing of risperidone in some soft-drinks
by HPLC method. 相似文献