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61.
Alain H. Roux Daniel Hétu Gérald Perron Jacques E. Desnoyers 《Journal of solution chemistry》1984,13(1):1-25
Mixed micelles can be formed in water between various pairs of hydrophobic solutes such as surfactants, alcohols and hydrocarbons. These systems can often be studied through the thermodynamic functions of transfer of one of the solutes, usually kept near infinite dilution, from water to an aqueous solution of the other solute. When mixed micelles are formed, these functions change significantly, and often go through extrema, in the region where the binary system micellizes or undergoes some microphase transition.Three main effects are responsible for the observed trends: pair-wise interactions between both solutes in the monomeric form, a distribution of the reference solute between the aqueous and micellar phases and a shift in the monomer-micelle equilibrium in the vicinity of the reference solute. Simple equations can be derived for these three effects which can account for the sign and magnitude of the observed trends using parameters which are derived for the most part from the two binary systems. 相似文献
62.
本文对月光花素甲(Calonyctin A)的整体分子结构分析加以完善并进行总结。前文报道月光花素甲是两个分子量相差28a.m.u的糖甙类同系物分子的混合物。这两个分子(简称M_1和M_2)分别称为月光花素甲(Ⅰ)与月光花素甲(Ⅱ)(Calonyctm A_1,CalonyctinA_2),分子量分别为938与910。它们分别含 相似文献
63.
A. Turck N. Pl D. Dognon C. Harmoy G. Quguiner 《Journal of heterocyclic chemistry》1994,31(6):1449-1453
The metalation of dihalogeno and halogenomethoxypyrazines was performed. The resulting pyrazines were submitted to a cross-coupling reaction with propargyl alcohol followed, after dehydration, by a catalytic reduction. This gives a new route to the synthesis of a key intermediate in the synthesis of arglecin. 相似文献
64.
Free chlorine evolved during the high-frequency induction furnace combustion of saline sediments at >1500°C interfered very seriously in the iodimetric titration of liberated sulphur dioxide. Remedies based on absorption of chlorine on copper, antimony and other traps were only partly successful; copper was the most efficient but the loss of titratable sulphur was still very large. Sample desalination with refluxing anhydrous methanol in a Soxhlet extractor was the only method found to give satisfactory performance. This procedure was successful for a broad range of salinity values (reference sample mixed with sodium chloride in ratios of 0.09–1.6) without affecting the sulphur minerals present. The procedure showed excellent precision and good agreement with the “best” values available for the USGS MAG-1 Marine Mud (0.40% S) with a relative standard deviation of 1.29%. Iodimetric determination of sulphur in salt core samples (with the sediment in minor proportions) would also be possible. 相似文献
65.
M. Oklobdija G. Comisso E. Decorte T. Kova
C. Angeli F. Moimas P. Zanon F. Zonno R. Toso V. unji 《Journal of heterocyclic chemistry》1983,20(5):1335-1338
Attempting some new approaches to 5,11-dihyro-6H-pyrido[2,3-b][1,4]benzodiazepin-6-one ( 6 ), compounds 8, 10 and 11 were prepared. Ring enlargement of 4 into 6 failed, as well as condensation of 10 and 11 into ID, which is the potential precursor of pirenzepin (11-[2′-(4″-methylpiperazin-1″-yl)]acetyl derivative of 6 ) via an envisaged intramolecular Diels-Alder reaction. Model compounds 5 and 13 were prepared and their behaviour in analogous reactions explained the failures of the intended transformations of 4 , as well as of condensation of 10 and 11 . 相似文献
66.
Benzalacetophenone reacts with anions derived from methyl chloroacetate and chloroacetonitrile (which are of the charge-localized type) at the carbonyl group to give α-epoxyalkenes. In contrast, the same ketone reacts with the anions derived from methyl phenylchloroacetate and phenylchloroacetonitrile (the negative charge of which is delocalized) to give cyclopropanes by attack at the carbon-carbon double bond. These results support the hypothesis that the reaction is charge-controlled with the former two reagents and orbital-controlled in the case of the latter two. Only one cyclopropane stereoisomer is formed in HMPA. 相似文献
67.
The reaction between copper (II) and azide has been studied spectrophotometrically at four wavelengths, at 25 degrees , and ionic strength 4.00M (sodium perchlorate). The formation constants beta(2) and beta(3) found are 2.90 +/- 0.08 x 10(4) and 3.02 +/- 0.07 x 10(6) respectively. The results obtained from potentiometric measurements with a solid-state electrode disagree with those calculated from the spectrophotometric data. Causes of the discrepancy are discussed. 相似文献
68.
《Tetrahedron: Asymmetry》2005,16(6):1233-1238
A series of new H8-BINOL-derived unsymmetrical hybrid ferrocenylphosphine-phosphoramidite ligands have been synthesized and successfully used in Rh-catalyzed asymmetric hydrogenations. The same or higher enantioselectivities (99.9% ee) were achieved in the hydrogenation of dimethyl itaconate and α-dehydroamino acid esters as those obtained with BINOL-derived analogues. However, slightly lower enantioselectivities (99.0% ee) were obtained in the hydrogenation of enamides. 相似文献
69.
70.
Derrida's random energy model is considered. Almost sure andL
P
convergence of the free energy at any inverse temperature are proven. Rigorous upper and lower bounds to the finite size corrections to the free energy are given. 相似文献