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1.
The applicability of (1R,2R)-1,3-diacetoxy-1-(4-nitrophenyl)-2-propyl isothiocyanate [(R,R)-DANI] as a recently developed chiral derivatizing agent for the enantioseparation of a series of β-blockers is described. The thiourea diastereomers formed were analyzed by reversed-phase high-performance liquid chromatography, mixtures of water and methanol or acetonitrile being used for elution. Conditions of derivatizations (temperature, reagent excess and reaction time) were optimized, and the effects of organic modifiers on the retention and separation were investigated; the diastereomers could readily be baseline separated with methanol-containing mobile phases with resolutions between 1.58 and 2.72. 相似文献
2.
Keiko N. A. Funtikova E. A. Stepanova L. G. Chuvashev Yu. A. Larina L. I. 《Russian Journal of Organic Chemistry》2002,38(7):970-976
Addition of thiols to 2-alkoxypropenal in neutral medium at 20°C in the absence of a catalyst occurs regioselectively, following the Markownikoff pattern. The resulting 2-alkoxy-2-R-thiopropanals are capable of undergoing spontaneous isomerization to 1-alkoxy-1-R-thiopropanones. The addition and isomerization processes are accelerated by heating to 60°C or in the presence of acid catalysts (TsOH, HCl). The reaction is also accompanied by partial disproportionation of 2-oxopropanal O,S-acetals to give O,O- and S,S-acetals. 相似文献
3.
WANGZhi LIZheng-qiang YuDa-hai WENGLiang LIUMing ZHANGGui-rong CAOShu-gui 《高等学校化学研究》2004,20(5):575-578
The lipases from different sources were screened for their ability to catalyze the resolution of 2-octanol in organic solvents with vinyl acetate as the acylating reagent. The medium effect has been studied on the irreversible transesterification with varying water activity(aw). The influence of vinyl acetate concentration on it has also been investigated. Under the optimal conditions, the enantiomeric ratio(E value) of pseudomonas fluorescence lipase (PFL) exceeded 200 with an enantiomeric excess (e. e. ) of S-2-octanol above 99% at a 51% degree of conversion. 相似文献
4.
《Physics and Chemistry of Liquids》2012,50(6):639-648
Viscosities of aqueous solutions of 2-propyne-1-ol (propargyl alcohol), 2-methyl-3-butyne-2-ol and 3-butene-2-ol have been measured at temperatures 308.15, 313.15, 318.15, 323.15 and 328.15?K over the entire composition range. Viscosity of the aqueous solutions of 2-methyl-3-butyne-2-ol and 3-butene-2-ol increases up to a maximum value and then starts decreasing almost linearly as the mole fraction of alcohol increases. 2-Methyl-3-butyne-2-ol + water and 3-butene-2-ol + water systems exhibit maxima around 0.5 and 0.2 mole fraction, respectively. Conversely, 2-propyne-1-ol + water system shows a rapid initial increase in viscosity up to 0.3 mole fraction followed by a slow steady increase as the mole fraction of alcohol increases to its pure state. Plots of excess viscosities against mole fraction of organic solutes for all the systems exhibit a sharp increase in η E to reach a well defined maxima, after which the curves show a descending trend. The variations of viscosity and excess viscosity with the composition of the mixtures have been interpreted in terms of hydrophobic and hydrophilic interactions between the species forming the mixtures. 相似文献
5.
Optically pure hydroxyphosphonates are widely used as derivatizable compounds that can be incorporated into a variety of synthetic strategies for the preparation of other high value organic products. A non-enzymatic kinetic resolution procedure to obtain chiral 2-hydroxy-2-arylethylphosphonates from the easily available racemic counterparts is described. A range of 2-hydroxy-2-arylethylphosphonates was efficiently resolved employing a planar-chiral DMAP derived catalyst with good selectivities (up to S=68). The chiral hydroxyphosphonates were isolated in good yields and high enantiomeric excess (>94% ee). 相似文献
6.
A series of 2-hydroxyaryl ketoximes were converted to the corresponding 1,2-benzisoxazole 2-oxides by treatment with iodobenzene diacetate (in acetic acid or methanol) or N-chlorosuccinimide in water. Both methods gave moderate to excellent yields for a variety of substituted oximes under mild conditions within short reaction times. The latter method has the advantages of an aqueous solvent and lack of halogenated organic by-products. 相似文献
7.
The adsorption of nitrobenzene, 2-chlorophenol, and 4-chlorophenol from water on organophilized derivatives of n-hexadecylpyridinium-montmorillonite (HDP-montmorillonite) was studied. Adsorption excess isotherms were obtained by the immersion
method and were analyzed to determine the adsorption capacity of organic pollutants on the hydrophobized surface. The basal
spacings of the clay minerals were determined by X-ray diffraction. The results of X-ray diffraction measurements are in good
agreement with excess isotherms: whenever a region of the isotherm indicates an increase for the adsorption of organic component,
an increase in basal spacing (interlamellar swelling) is also observed. By combining these two independent methods, composition
and structure of the interlamellar space between the silicate layers could be accurately calculated. The free enthalpy of
adsorption, the adsorption capacity, and the separation factor for adsorption are calculated by analyzing the adsorption isotherm
on the basis of the Gibbs equation and Everett-Schay method. The results are utilizable for planning environmental procedures
and systems (water clarification and soil remediation).
Received: 17 July 2000 Accepted: 5 October 2000 相似文献
8.
Environmentally Sustainable and Chemo‐selectively Favorable Synthesis of Substituted 2H‐Pyran‐2‐ones in Water under MWI
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In this paper, a novel synthesis of diversely substituted 2H‐pyran‐2‐ones via the tandem reaction of 3‐hydroxyhexa‐4,5‐allenic esters in water under the promotion of MWI has been developed. Compared with those reactions carried out in organic solvents, water mediated synthesis of poly‐substituted 2H‐pyran‐2‐ones is not only environmentally sustainable, but also chemo‐selectively favorable. 相似文献
9.
《Physics and Chemistry of Liquids》2012,50(2):262-271
The density (ρ), viscosity (η) and ultrasonic velocity (u) of three mixtures consisting of 2- pyrrolidone with 1,3-propanediol (PD) and water and also of PD and water have been measured as a function of mole fraction at 308.15 K. The experimentally collected data has been used to calculate the excess molar volume (VE), deviation in viscosity (Δη), deviation in ultrasonic velocity (Δu), isentropic compressibility (κs), deviation in isentropic compressibility (Δκs) and excess Gibbs free energy of activation (ΔG*E). The Redlich–Kister polynomial equation has been used to fit the derived parameters. The variation in excessive thermodynamic properties as a consequence of possible molecular interactions is discussed. 相似文献
10.
《Physics and Chemistry of Liquids》2012,50(2):151-168
Abstract Densities (ρ) of the ternary mixtures 2-methoxyethanol +1,2-dimethoxyethane + water have been measured at 19 temperatures in the range - 263.15 ≤ T/K ≤ 353.15. The experimental data were processed by empirical relations accounting for the dependence of ρ on temperature and ternary composition expressed as mole fraction of the components (0≤xi ≤1). All checked equations seem to be suitable for correlation purposes, in order to obtain interpolated values in correspondence to experimental data gaps. Furthermore, the excess molar volume (VE ) has been investigated to make evident the possibility of forming stable solvent-cosolvent adducts. The excess property has been interpreted on the basis of specific intermolecular interactions between the components. 相似文献
11.
Enzymatic Enantioselective Synthesis of (R)-2-Trimethylsilyl-2-hydroxyl-propionitrile by Defatted Apple Seed Meal 总被引:1,自引:0,他引:1
IntroductionOverthepastyears ,thesynthesisofchiralaldehyde cyanohydrinswaswellstudied .1Incontrasttochiralalde hyde cyanohydrins ,therewereonlyfewreportsaboutthepreparationofopticallyactiveketone cyanohydrins ,2 whichareusefulstartingmaterialsandintermediatesforthesyn thesisofmanychiralnaturalproducts .3Wethereforefo cusedonthepreparationofopticallyactivesiliconcontain ing (R ) ketone cyanohydrin ((R ) 2 trimethylsilyl 2 hy droxyl propionitrile)usingacetonecyanohydrinastran scyanationagen… 相似文献
12.
《Physics and Chemistry of Liquids》2012,50(3):291-295
Densities (ρ) at five temperatures, between 293.15 and 313.15?K, of binary mixtures of dipropylene glycol monomethyl ether + water and dipropylene glycol monomethyl ether + 2-methoxyethanol, are reported. The excess molar volumes (V E ) were calculated from these experimental data. The results are discussed in terms of intermolecular interactions. 相似文献
13.
Gérard Douhéret Alain H. Roux Michael I. Davis Maria Elena Hernandez Harald Høiland Einar Høgseth 《Journal of solution chemistry》1993,22(11):1041-1062
The densities and the ultrasonic speeds of the aqueous solutions of 2-(2-hexyloxyethoxy)ethanol (C6E2) were measured over the entire range of mole fractions at 5°C. Excess molar volumes V
E
were readily calculated from the densities. The densities, in combination with the ultrasonic speeds, furnish estimates of the molar (and excess molar) isentropic compressibilities K
S
and the deviations u
D
of the ultrasonic speeds from the values calculated for ideal mixtures. Radical changes in the mole fraction derivatives of the excess molar properties of the (C6E2 + water) system, in the vicinity of an amphiphile mole fraction of 0.003, indicate that C6E2 like C6E3 is capable of micelle formation. Our data have been compared with those reported earlier for (C4E2 +, C2E2 +, and C6E3 + water). We have employed both mass action and pseudophase approaches to data analysis, together with the four-segment model approach. 相似文献
14.
M. A. Sibiryakova G. F. Muzychenko S. D. Burlaka K. S. Pushkareva V. G. Glukhovtsev Z. I. Tyukhteneva 《Chemistry of Heterocyclic Compounds》2002,38(5):533-538
The nucleophilic addition of n-butyl- and benzylamines to 1-(4-nitrophenyl)-5H-pyrrolin-5-one and 1-(4-sulfamoylphenyl)-5H-pyrrolin-2-one at 50°C in an excess of the amines with the formation of N-substituted amides of 3-alkyl(benzyl)amino-4-(4-R-anilino)butyric acids was investigated. The N-substituted amides of 3-arylamino-4-hydroxybutyric and 4-hydroxy-2-butenoic acids were synthesized from 2(5H)-furanone and aromatic amines (1:3) at 180°C. 4-Alkylamino-1-(4-nitrophenyl)pyrrolid-2-ones were obtained in the reaction of 1-(4-nitrophenyl)-5-pyrrolin-2-one with ammonia or aliphatic, alicyclic, and aromatic amines (1:3, 90°C, in DMF). 相似文献
15.
Excess isobaric heat capacities of mixture (2-methoxyethanol+water) were measured at T=298.15 K and excess enthalpies at T=293.15 and 298.15 K. Excess enthalpies were extremely exothermic, up to -1290 J mol-1 atT=293.15 K and -1240 J mol-1 at T=298.15 K. Excess isobaric heat capacities were positive and very large, approximately 9 J K-1 mol-1 at the maximum. In contrast to the data reported by Page and coworkers, the excess heat capacity data were positive in the
entire composition range and there was no change in their signs. Consistently, no crossing was found between the curves of
excess enthalpies at T=298.15 and 293.15 K.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Rate constants of the reactions of O(3P) atoms with Br2 and NO2 over the temperature range 220-950 K
The kinetics of the reactions of Br2 and NO2 with ground state oxygen atoms have been studied over a wide temperature range, T = 220-950 K, using a low-pressure flow tube reactor coupled with a quadrupole mass spectrometer: O + NO2 → NO + O2 (1) and O + Br2 → Br + BrO (2). The rate constant of reaction (1) was determined under pseudo–first-order conditions, either monitoring the kinetics of O-atom or NO2 consumption in excess of NO2 or of the oxygen atoms, respectively: k1 = (6.1 ± 0.4) × 10−12 exp((155 ± 18)/T) cm3 molecule−1 s−1 (where the uncertainties represent precision at the 2σ level, the estimated total uncertainty on k1 being 15% at all temperatures). The temperature dependence of k1, found to be in excellent agreement with multiple previous low-temperature data, was extended to 950 K. The rate constant of reaction (2) determined under pseudo–first-order conditions, monitoring the kinetics of Br2 consumption in excess of O-atoms, showed upward curvature at low and high temperatures of the study and was fitted with the following three-parameter expression: k2 = 9.85 × 10−16 T1.41 exp(543/T) cm3 molecule−1 s−1 at T = (220-950) K, which is recommended from the present study with an independent of temperature conservative uncertainty of 15% on k2. 相似文献
17.
Chenxu Ding Xuejun Sun Xianen Zhao Wenchen Zhao Yulin Li Honglun Wang Yourui Suo Jinmao You 《Chromatographia》2008,67(3-4):245-251
A pre-column derivatization method for sensitive determination of oligopeptides, using the tagging reagent 2-(9-carbazole)ethyl
chloroformate (CEOC-Cl) followed by capillary electrophoresis (CE) with diode-array detection, has been developed. Maximum
yield close to 100% were observed when a three to fourfold molar excess of reagent was used at pH 9.0–10.0. Excess reagent
was extracted with n-hexane–ethyl acetate 9:1–10:1 (v/v); this enabled direct analysis using CE with no significant disturbance from the major fluorescent reagent degradation by-products.
The effects on the results of buffer pH and of SDS and organic modifier concentrations were examined. Good baseline resolution
in the separation of five CEOC-peptides was achieved with a 48.5-cm total length (effective length 40 cm) 50-μm inner diameter
capillary column. 相似文献
18.
Xiang-Da Zhang Shu-Zhen Hou Jian-Xiang Wu Prof. Dr. Zhi-Yuan Gu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(7):1604-1611
The electrochemical reduction of CO2 presents a promising strategy to mitigate the greenhouse effect and reduce excess carbon dioxide emission to realize a carbon-neutral energy cycle, but it suffers from the lack of high-performance electrocatalysts. In this work, catalytic active cobalt porphyrin [TCPP(Co)=(5,10,15,20)-tetrakis(4-carboxyphenyl)porphyrin-CoII] was precisely anchored onto water-stable 2D metal–organic framework (MOF) nanosheets (Zr-BTB) to obtain ultrathin 2D MOF nanosheets [TCPP(Co)/Zr-BTB] with accessible catalytic sites for the CO2 reduction reaction. Compared with molecular cobalt porphyrin, the TCPP(Co)/Zr-BTB exhibits an ultrahigh turnover frequency (TOF=4768 h−1 at −0.919 V vs. reversible hydrogen electrode, RHE) owing to high active-site utilization. In addition, three post-modified 2D MOF nanosheets [TCPP(Co)/Zr-BTB-PABA, TCPP(Co)/Zr-BTB-PSBA, TCPP(Co)/Zr-BTB-PSABA] were obtained, with the modifiers of p-(aminomethyl)benzoic acid (PABA), p-sulfobenzoic acid potassium (PSBA), and p-sulfamidobenzoic acid (PSABA), to change the micro-environments around TCPP(Co) through the tuning of steric effects. Among them, the TCPP(Co)/Zr-BTB-PSABA exhibited the best performance with a faradaic efficiency (FECO) of 85.1 %, TOF of 5315 h−1, and jtotal of 6 mA cm−2 at −0.769 V (vs. RHE). In addition, the long-term durability of the electrocatalysts is evaluated and the role of pH buffer is revealed. 相似文献
19.
《Journal of Coordination Chemistry》2012,65(3):189-199
Abstract The crystal structures of ammonium and sodium 2-amino-3,5-dichlorobenzoates were determined by the X-ray diffraction method. The ammonium salt crystallizes in the monoclinic system (space group P21/c) with a = 13.941(3), b = 9.128(3), c = 7.349(2) Å, β = 90.80(3)° and Z = 4. The structure consists of an ammonium cation hydrogen bonded to a carboxylate oxygen of the 2-amino-3,5-dichlorobenzoate anion. The sodium salt of 2-amino-3,5-dichlorobenzoic acid crystallizes in the triclinic system (space group P 1) with a = 8.033(2), 6 = 8.944(2), c = 17.350(3) Å, α = 76.72(3)°, β = 79.69(3)°, γ = 72.54(3)° and Z = 4. The compound is a polymer in which the sodium ions are coordinated by carboxylate oxygen atoms of the organic ligand and water molecules in an octahedral arrangement. IR spectra of the salts are discussed. 相似文献
20.
In this paper, we developed low molecular weight gel system based on cholesterol derivative containing pyridine unit attached through β-alanine linkage, which can act as efficient gelator to form novel gel systems in organic or organic–water solvents. Spherical nanoscale anatase–TiO2 with porous structure was obtained through the in situ hydrolysis in the gel tissue upon the instant addition of water followed by calcination, which had photo catalytic activity toward naphthol blue black. To the best of our knowledge, this is the first example that cholesterol-based gel tissue was employed as the template to construct TiO2 with photo-catalytic activity. 相似文献