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1.
Large-angle X-ray Scattering (LAXS) experiments at 298 K have been made on 1-propanol–water mixtures over the whole 1-propanol mole fraction range. The radial distribution functions show that the predominant clusters in 1-propanol–water mixtures change at 1-propanol mole fraction x 1pr = 0.1; the tetrahedral-like structure of water is mainly formed in the mixtures with x 1pr≤ 0.1, while hydrogen-bonded chain clusters of 1-propanol molecules predominate in the mixtures at x 1pr > 0.1. From the present results, together with the previous ones on methanol–water, ethanol–water, and 2-propanol–water mixtures, size and shape effects of the hydrophobic groups on the structure of aliphatic alcohol–water mixtures are discussed at the molecular level. The anomalies of the enthalpies of mixing for 1-propanol–water mixtures at 298 K are interpreted on the basis of the proposed change in structure of the mixtures with 1-propanol mole fraction.  相似文献   

2.
The competitive bulk liquid membrane transport of Cr3+, Co2+, Cu2+, Zn2+, Cd2+, Ag+ and Pb2+ metal cations with a new synthetic sulfur donor acyclic ligand (pseudo-cyclic ionophore), i.e. 1-(2-[(2-hydroxy-3-phenoxypropyl)sulfanyl]ethylsulfanyl)-3-phenoxy-2-propanol; (C20H26O4S2), was examined using some organic solvents as membranes. The membrane solvents include: chloroform (CHCl3), 1,2-dichloroethane (1,2-DCE), dichloromethane (DCM), nitrobenzene (NB), chloroform-nitrobenzene (CHCl3-NB) and chloroform-dichloromethane (CHCl3-DCM) binary mixtures. The transport process was driven by a back flux of protons, maintained by the buffering the source and receiving phases with pH 5 and 3, respectively. The aqueous source phase consisted of a buffer solution (CH3COOH/CH3COONa) at pH = 5 and containing an equimolar mixture of these seven metal cations. The organic phase contained the acyclic ligand, as an ionophore and the receiving phase consisted of a buffer solution (HCOOH/HCOONa) at pH = 3. For these systems that displayed transport behaviour, sole selectivity for Ag+ cation was observed under the employed experimental conditions in this investigation. The amount of Ag+ transported follows the trend: 1,2-DCE > CHCl3 > DCM > NB in the bulk liquid membrane studies. The transport of the metal cations in CHCl3-NB and CHCl3-DCM binary solvents is sensitive to the solvent composition. The influence of the stearic acid, palmitic acid and oleic acid in the membrane phase on the ion transport was also investigated.  相似文献   

3.
The macroscopic and microscopic acid-base chemistry of a series of sulfhydryl and ammonium-containing amino acids HS–R–NH3 [R=–CH2CH(COOH)–, cysteine (CYS); R=–C(CH3)2CH(COOH)–, penicillamine (PEN); R=–CH(COOH)CH2CH2CONHCH(–CH2)CONHCH2COOH, glutathione (GSH)] was characterized in water and its binary mixtures with acetonitrile (16.3, 34.2, and 53.9 mass % acetonitrile). Macroscopic acid dissociation constants were obtained by potentiometric titration using the glass-calomel electrode pair. Microscopic acid dissociation constants were calculated from ultraviolet absorption measurements at ca. 232 nm where the deprotonated sulfhydryl group absorbs. The macroscopic constants decrease uniformly as the solvent becomes enriched in acetonitrile. The microscopic constants, which characterize the relative concentrations of the two monoprotonated tautomers of the molecules (I and II) reveal that as the solvent becomes enriched in acetonitrile, the fraction of molecules existing as highly charged tautomer I decreases for CYS (0.68–0.40), PEN (0.85–0.34), and GSH (0.61–0.30). These results are related to the decreasing concentration of water as the solvent becomes enriched in acetonitrile.  相似文献   

4.
Abstract

The ligand exchange reaction between [M(phen)3]2+ and [M(DIP)3]2+ (where M is the same and M = FeII or NiII, phen = 1,10-phenanthroline, DIP = 4,7-diphenyl-1,10-phenanthroline) has been investigated by reversed phase ion-paired chromatography (RP-IPC). The effect of pH and solvent on the ligand-exchange reaction is studied by monitoring the variation in chromatograms with time after mixing. The results have shown that the ligand exchange reaction between [M(phen)3]2+ and [M(DIP)3]2+ takes place in the pH range of 3–8 and the rate of reaction for nickel(II) complexes is about two times slower than that for iron(II) complexes. Experiments on the effect of various solvents on the ligand-exchange reaction have revealed that the rate of reaction is enhanced by the solvent in the following order: (CH3)2CO > CHCl3 ≥ CH2Cl2 > CH3CN > CH3OH. Elemental analysis and UV-visible spectroscopy confirmed that the products obtained from the ligand-exchange reaction are mixed-ligand complexes containing phen and DIP ligands, i.e., [M(phen)2(DIP)]2+ and [M(phen)(DIP)2]2+.  相似文献   

5.
A serial of late transition metal complexes, which bearing Benzocyclohexane–ketoarylimine ligand and named as Mt(benzocyclohexane–ketoarylimino)2 {Mt(bchkai)2: Mt=Ni or Pd; bchkai=C10H8(O)CN(Ar)CH3; Ar=naphthyl or fluoryl}, have been synthesized and characterized. The molecular structures of the ligands and nickel complex have been confirmed by X‐ray single‐crystal analyses. The nickel complexes exhibited very high activity up to 2.7 × 105 gpolymer/molNi·h and palladium complexes showed high activity up to 2.3 × 105 gpolymer/molPd·h for norbornene (NB) homo‐polymerization with tris(pentafluorophenyl)borane as cocatalyst. The four complexes were effective for copolymerization of NB and 5‐norbornene‐2‐carboxylic acid methyl ester (NB‐COOCH3) in relatively high activities (0.1–2.4 × 105 gpolymer/molMt·h) and produced the addition‐type copolymers with relatively high molecular weights (0.5 × 105–1.2 × 105 g/mol) as well as narrow molecular weight distributions (PDI < 2 for all polymers). Influences of the metals and comonomer feed content on the polymerization activity as well as on the incorporation rates (20.9–42.6%) were investigated. The achieved NB/NB‐COOCH3 copolymers were confirmed to be noncrystalline, exhibited good thermal stability (Td > 400°C) and showed good solubility in common organic solvents. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

6.
The orientation of the isopropyl group at the liquid/vapor interface in 2-propanol/water binary mixtures was studied by vibrational sum frequency spectroscopy. The CH(3) stretch modes of the two methyl groups were used to determine the molecule's orientation by employing a novel united atom approach to model the (CH(3))(2)X moiety. For this purpose, the changes in the molecular susceptibility of the isopropyl group stretches were derived in the laboratory frame as a function of the tilt and twist angles. The results indicated that the methyl groups lay down on the surface at low alcohol mole fraction and gradually twisted with increasing mole fraction. At the azeotrope, x(iso) = 0.68, one of the methyl groups aligned approximately parallel to the surface normal, whereas the other was nearly parallel with the liquid/vapor interface. When the mole fraction of 2-propanol was higher than 0.68, the orientation of 2-propanol remained almost constant. The change in the alcohol's orientation with 2-propanol mole fraction closely tracked changes in its bulk activity coefficient. Such results lead to a picture in which the surface structure and bulk properties of the system are closely linked.  相似文献   

7.
The relative permittivities (?r20) of 4-dimethylaminostyrene (I) and of 0.5–3.0 M solutions of N,N-dimethyl-4-toluidine (DMT) were measured in nitrobenzene (NB) and in a mixture of NB with diisopropyl ether (NB + E), the DMT solutions modelled those of I. An increase in [DMT] from 0.5 to 3.0 M caused a decrease in ?r20 from 32.3 to 18.3 in NB, while only from 20.8 to 18.3 in (NB + E) at fixed [NB]. The great difference between the ?r20 of 0.5 and 3.0 M DMT solutions in NB explains the previously observed drop in the percentage rate of polymerization (RP) of I, in NB initiated with CCl3COOH, with increasing [I]o. In (NB + E) mixture with fixed [NB], the percentage RP and the limiting viscosity number [ν] of polyl increase with increasing [I]o. The observed dependences of both RP (in Msec?1) and [ν] on [I]0 confirm the validity of the suggested polymerization scheme for I initiated with CCl3COOH, and make possible determination of the characteristics of the elementary polymerization reactions.  相似文献   

8.
Ni/Sup catalysts were prepared, where SBA-15, γ-Al2O3, SiO2 were used as supports (Sup). The synthesized catalysts were investigated by the methods of low-temperature nitrogen adsorption, temperatureprogrammed reduction (TPR), and high-resolution transmission electron microscopy. The catalytic properties of the prepared catalysts were tested in liquid phase hydrogenation of biphenyl under conditions of a flow installation at temperatures of 60–100°C, pressure of 4 MPa, volumetric feed rate of 4–10 h–1 and H2: feed ratio of 1500 nM.. A 1 wt % solution of biphenyl in heptane,, as a model mixture, was used. It has been established that the activity of nickel hydrogenation catalysts depends on the nickel content and the type of support. The activity of supported nickel catalysts decreases in the series Ni-12/SBA-15 > Ni-12/SiO2 >> Ni-12/Al2O3. The kinetic characteristics of the biphenyl hydrogenation reaction were determined: the rate constants and activation energy for the hydrogenation of the first and second aromatic rings of the substrate molecule.  相似文献   

9.
Tertiary amino resins (TAR) were chemically modified by quaternization with methyl iodide. By this route six partly quaternized tertiary amino resins (PQTAR) with different I/N mole ratio were synthesized. Four different reducing agents, i.e., NaH, LiAlH4, CH3OH-NaOH and NaBH4, were tested for the preparation of palladium catalysts dispersed on TAR or PQTAR. The rate of hydrogenation of methyl acrylate and the amount of Pd leached from the catalysts during the hydrogenation reaction were found to be dependent not only on the type of reducing agent but also on the structure of polymer support. Both the rate of hydrogenation and the amount of Pd eluted closely relate to the I/N mole ratio of the polymer supports.  相似文献   

10.
Abstract

Viscosities of the systems, water (W) + n-butylamine (NBA), W + sec-butylamine (SBA) and W + tert-butylamine (TBA) have been measured in the temperature range 298.15–323.15K. The viscosities (η) and excess viscosities (ηE) have been plotted against mole fraction of amines (X 2). On addition of amines to water, viscosities first increase rapidly, then pass through maxima at 0.2 mole fraction of amines and then decline continuously as the addition of amines is continued. ηE show large positive values, with maxima also at 0.2 mole fraction of amines. The maxima of the curves of η and ηE vs. mole fraction of butylamines follow the order, W + TBA > W + SBA > W + NBA. The ascending part of the η vs. X 2 curves in the water-rich region is explained by the hydrophobic hydration caused by the hydrocarbon tails and the hydrophilic effect due to — NH2 group of amines. Following the maxima, amine - amine association is preferred, which accounts for the steady decrease of viscosity up to the pure state of amines.  相似文献   

11.
The compositions, stability constants, and rate constants of intramolecular redox decomposition of cerium(IV) complexes with anions of aminoacetic (H2NCH2COOH), iminodiacetic [HN(CH2COOH)2], nitrilotriacetic [N(CH2COOH)3], ethylenediaminetetraacetic [(CH2COOH)2N(CH2)2N(CH2COOH)2], and hexamethylenediaminetetraacetic [(CH2COOH)2N(CH2)6N(CH2COOH)2] acids were determined by potentiometric, spectrophotometric, and kinetic methods at pH in the range 1.3?2.0 in perchlorate and nitrate media at an ionic strength I = 0.1 and a temperature of 298.15 K. Direct linear correlation between the logarithms of the stability constants of the complexes, log β101, and logarithms of the cumulative protonation constants, log В m+k (k = 1–2), of aminopolyacetic acid anions L m–, and inverse linear correlation between log β101 and logarithms of the rate constants of intramolecular redox decomposition of the complexonates [CeL]4–m (m = 1–4), log k n=1, were found.  相似文献   

12.
The values of the fraction of ionizes phenyl salicylate, fPS-, obtained from initial absorbance measurement of phenyl salicylate at 350 nm, remain unchanged with the increase in [CH3CO2Na] from 0.0 to 0.7 M at 0.01 M NaOH (fPS- ≈ 0.70) and 0.02 M NaOH (fPS- ≈ 0.93). The values of fPS- decrease from ~ 1.0 to 0.90 and ~ 1.0 to 0.84 with the increase in respective [CH3CO2Na] and [NaBr] from 0.0 to 0.6 M at 0.01 M NaOH, 0.02 M C12E23(=C12H25(OCH2CH2)23OH) and 0.01 M CTABr (=C16H33NMe3Br).  相似文献   

13.
A palladium-based catalytic system is highly active in the synthesis of γ-keto acids of type ArCOCH2CH2COOH via carbonylation-decarboxylation of the corresponding α-chloride. Typical reaction conditions are: P(CO) = 20–30 atm; substrate/H2O/Pd = 100–400/800–1000/1 (mol); temperature: 100–110 °C; [Pd]=0.25 × 10−2−1 × 1O−2 M; solvent: acetone; reaction time: 1–2 h. A palladium(II) complex can be used as catalyst precursor. Under the reaction conditions above, reduction of the precursor to palladium metal occurs to a variable extent. High catalytic activity is observed when the precursor undergoes extensive decomposition to the metal. Pd/C is also highly active. Slightly higher yields are obtainable when the catalytic system is used in combination with a ligand such as PPh3. A mechanism for the catalytic cycle is proposed: (i) The starting keto chloride undergoes oxidative addition to reduced palladium with formation of a catalytic intermediate having a Pd-[CH(COOH)CH2COPh] moiety. The reduced palladium may be the metal coordinated by other atoms of palladium and/or by carbon monoxide and/or by a PPh3 ligand when catalysis is carried out in the presence of this ligand. It is also proposed that the keto group in the β-position with respect to the carbon atom bonded to chlorine weakens the CCl bond, easing the oxidative addition step and enhancing the activity of the catalyst. (ii) Carbon monoxide ‘inserts’ into the PdC bond of the above intermediate to give an acyl catalytic intermediate having a Pd-[COCH(COOH)CH2COPh] moiety. (iii) Nucleophilic attack of H2O to the carbon atom of the carbonyl group bonded to the metal of the acyl intermediate yields a malonic acid derivative as product intermediate. This, upon decarboxylation, gives the final product. Alternatively, the desired product may form without the malonic acid derivative intermediate, through the following reaction pathway: the acyl intermediate undergoes decarboxylation with formation of a different acyl intermediate, having a Pd-[CO-CH2CH2COPh] moiety, which, upon nucleophilic attack of H2O on the carbon atom of the carbonyl group bonded to the metal, yields the final product.  相似文献   

14.
Lanthanum nitrate distribution in three-component aqueous-organic systems with D2EHPA from acetate or acetic acid–acetate solutions has been studied, it has been shown that variation in sodium acetate concentration or composition of CH3COONa–CH3COOH mixture can affect metal distribution ratios. It has been found that extraction in three-component mixture of 1: 1: 1 composition (aqueous solution Ln(NO3)3 + CH3COONa + CH3COOH–D2EHPA in hexane–isopropyl alcohol) can provide lanthanide separation, which is dependent on the ratio of sodium acetate and acetic acid in aqueous phase and on D2EHPA concentration in organic phase. Lanthanide–lanthanum separation factors have been calculated for the extraction of lanthanide nitrates from acetic acid–acetate solutions.  相似文献   

15.
In this work, the aqueous phase diagram for the mixture of the hydrophilic tributyltetradecyl phosphonium ([P44414]Cl) ionic liquid with acetic acid (CH3COOH) is determined, and the temperature dependency of the biphasic region established. Molecular dynamic simulations of the [P44414]Cl + CH3COOH + H2O system indicate that the occurrence of a closed “type 0” biphasic regime is due to a “washing-out” phenomenon upon addition of water, resulting in solvophobic segregation of the [P44414]Cl. The solubility of various metal oxides in the anhydrous [P44414]Cl + CH3COOH system was determined, with the system presenting a good selectivity for CoO. Integration of the separation step was demonstrated through the addition of water, yielding a biphasic regime. Finally, the [P44414]Cl + CH3COOH system was applied to the treatment of real waste, NiMH battery black mass, being shown that it allows an efficient separation of Co(II) from Ni(II), Fe(III) and the lanthanides in a single leaching and separation step.  相似文献   

16.
The thermal decomposition of formaldehyde was investigated behind shock waves at temperatures between 1675 and 2080 K. Quantitative concentration time profiles of formaldehyde and formyl radicals were measured by means of sensitive 174 nm VUV absorption (CH2O) and 614 nm FM spectroscopy (HCO), respectively. The rate constant of the radical forming channel (1a), CH2O + M → HCO + H + M, of the unimolecular decomposition of formaldehyde in argon was measured at temperatures from 1675 to 2080 K at an average total pressure of 1.2 bar, k1a = 5.0 × 1015 exp(‐308 kJ mol?1/RT) cm3 mol?1 s?1. The pressure dependence, the rate of the competing molecular channel (1b), CH2O + M → H2 + CO + M, and the branching fraction β = k1a/(kA1a + k1b) was characterized by a two‐channel RRKM/master equation analysis. With channel (1b) being the main channel at low pressures, the branching fraction was found to switch from channel (1b) to channel (1a) at moderate pressures of 1–50 bar. Taking advantage of the results of two preceding publications, a decomposition mechanism with six reactions is recommended, which was validated by measured formyl radical profiles and numerous literature experimental observations. The mechanism is capable of a reliable prediction of almost all formaldehyde pyrolysis literature data, including CH2O, CO, and H atom measurements at temperatures of 1200–3200 K, with mixtures of 7 ppm to 5% formaldehyde, and pressures up to 15 bar. Some evidence was found for a self‐reaction of two CH2O molecules. At high initial CH2O mole fractions the reverse of reaction (6), CH2OH + HCO ? CH2O + CH2O becomes noticeable. The rate of the forward reaction was roughly measured to be k6 = 1.5 × 1013 cm3 mol?1 s?1. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 157–169 2004  相似文献   

17.
A series of functional polyethylenes have been simply and efficiently synthesized via the combination of regioselective ethylene/5‐vinyl‐2‐norbornene (VNB) copolymerization using [PhNC(CF3)CHCO(Ph)]2TiCl2 catalyst and following ultraviolet light initiated thiol‐ene click reaction. On treatment of ethylene/VNB copolymer with different thiols including mercaptoethanol, 1‐thioglycerol, methyl mercaptoacetate, methyl mercaptopropionate, 2‐mercaptoethylamine, mercaptoacetic acid, and mercaptopropanoic acid, various polar groups have been successfully introduced into the polyethylene. Except 2‐mercaptoethylamine, the functionalizations are quite efficient with the degree of functionalization higher than 94%, which is independent of thiol structure and double bond content. The content of polar group in functional polyethylene can be tuned in a wide range of 0–30 mol %. Gel permeation chromatography profiles indicate all functional polyethylenes that have very high molecular weights (160–336 kg/mol) with homogeneous formation. Besides, systematic investigation of the influence of vinyl type and thiol structure on reactivity has been also carried out. By treatment of mercaptoethanol with different copolymers (ethylene/VNB, ethylene/5‐ethylidene‐2‐norbornene, and ethylene/dicyclopentadiene copolymer), the order of vinyl reactivity can be summarized as terminal > internal > cyclic double bond. For different thiols, the reactivity has the sequence of SHCH2COOH > SHCH2COOCH3 > SHCH2CH2COOH > SHCH2CH2COOCH3 > SHCH2CH(OH)CH2OH > SHCH2CH2OH > SHCH2CH2NH2, which is depended on the solubility and the electron‐withdrawing inductive effect of polar group. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

18.
Studies on photo-catalytic reduction of CO2 using TiO2 photo-catalyst (0.1%, w/v) as a suspension in water was carried out at 350 nm light. CO2 from both commercially available source, as well as generated in situ through 2-propanol oxidation, was used for this study. The photolytic products such as hydrogen (H2), carbon monoxide (CO) andmethane (CH4) generated were monitored in TiO2 suspended aqueous solution with and without a hole scavenger, viz., 2-propanol. Similar photolytic experiments were also carried out with varying ambient such as air, O2, N2 and N2O. The yields of CO and CH4 in all these systems under the present experimental conditions were found to be increasing with light exposure time. H2 yield in N2-purged systems containing 2-propanol was found to be more as compared to the without 2-propanol system. The rate of H2 production in N2-purged aqueous solutions containing 0.1% TiO2 suspension were evaluated to be 0.226 and 5.8 μl/h, without and with 0.5 M 2-propanol, respectively. This confirmed that 2-propanol was an efficient hole scavenger and it scavenged photo-generated holes (h+), allowing its counter ion, viz., e, to react with water molecule/H+ to yield more H2. The formation of both CO and CH4 in the photolysis of CO2-purged aqueous solutions containing suspended TiO2 in absence of 2-propanol reveal that the generation of CH4 is taking place mainly through CO intermediate. In presence of air/O2, the yield of H2 in the system without 2-propanol was observed to be negligible as compared to the system containing 2-propanol in which low yield of H2 was obtained with a formation rate of approx. 0.5 μl/h.  相似文献   

19.
高汉荣  徐筠 《分子催化》1993,7(6):432-438
报道了四种不同P/Pd摩尔比的膦化聚2,6-二甲基1,4-苯醚负载把催化剂的加氢和异构化性能;通过XPS、电镜和远红外对催化剂进行了表征;并考察了溶剂和温度对催化剂活性的影响.  相似文献   

20.
Zusammenfassung Bei Verwendung einer automatisch arbeitenden potentiometrischen Apparatur (Titrator TTT 1c + Titrigraph SBR 2c, Radiometer) kann freie Essigsäure in Anwesenheit von Metallsalzen mit ausreichender Genauigkeit zur Untersuchung von Essigsäuresolvaten, wie z. B. NiCl2·0,5 CH3COOH, CuCl2·0,5 CH3COOH, PbCl(CH3COO)·CH3COOH, bestimmt werden.
Summary Using an automatically working potentiometric apparatus (Titrator TTT 1c + Titrigraph SBR 2c, Radiometer) free acetic acid can be determined in presence of metal salts with sufficient exactness to analyze acetic acid solvates, i.e. NiCl2·0.5 CH3COOH, CuCl2·0.5 CH3COOH, PbCl(CH3COO)·CH3COOH.


Die Verfasser danken der Deutschen Forschungsgemeinschaft und der Wissenschaftlichen Gesellschaft des Saarlandes e.V. für die Förderung dieser Untersuchungen durch Sachmittel.  相似文献   

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