用气相色谱法研究乙酸乙烯酯不对称氢甲酰化反应中溶剂的影响

用毛细管气相色谱、色－质谱和旋光色散及圆二色性谱仪等方法对乙酸乙烯酯在非极性和极性溶剂中的不对称氢甲酰化反应产物进行分离和鉴定。实验结果表明,在非极性溶剂中反应的收率、选择性、光学收率ｅ．ｅ．值（ｅｎａｎｔｉｏｍｅｒｉｃｅｘｃｅｓｓ）均比极性溶剂中的结果为好。由此探讨了不对称氢甲酰化反应中溶剂的影响。     

四苯硼钾由单-到不同混合溶剂的迁移自由能

KBPh4作为一种典型的大阴离子电解质 ,在研究与计算大分子电解质的迁移热力学性质中起着重要的作用 .讨论大分子电解质与不同溶剂间的作用 ,还可以为萃取、色谱及表面活性剂的研究提供理论依据 .一些文献及我们前文曾对四苯硼盐由水到一些纯溶剂 [1,2]及从水到某些水-有机混合溶剂中的标准迁移自由能进行了研究 [3],但对四苯硼盐在有机-有机混合溶剂中的研究报导极少 .本文对 KBPh4由水到水-异丙醇和由甲醇到甲醇-异丙醇混合溶剂的标准迁移自由能进行了研究和探讨 .1实验部分 1.1实验仪器及方法 　　用 CS501型超级恒温槽恒温 ;用 WF…     

Solvation of the Whelk-O1 chiral stationary phase: a molecular dynamics study

Density functional theory calculations and molecular dynamics simulations are employed to explore the solvation of the Whelk-O1 chiral stationary phase. First, a semi-flexible representation of the Whelk-O1 selective molecule is extracted from an extensive series of B3LYP/6-311+ G(2d,p) calculations. The resulting model is used to build a chiral surface, including end-caps, for molecular dynamics study of the interface between solvent and Whelk-O1. Three solvent environments in common use for Whelk-O1 HPLC have been examined: a normal-phase solvent of n-hexane/2-propanol; a reversed-phase solvent of water/methanol; and a supercritical solvent of CO(2) and methanol. In each case, we analyze the interface with an emphasis on solvent composition and solvent hydrogen bonding to the Whelk-O1 selector.     

Solvent effects on the redox properties of thioethers

The one-electron reduction potential of the radical cations of thioanisole (1), benzyl methyl sulfide (2) and 2-hydroxyethyl benzyl sulfide (3) in water, formamide, acetonitrile, acetone, 1,1,1,3,3,3-hexafluoropropan-2-ol, methanol and 2-propanol was investigated by cyclic voltammetry. For comparison the one-electron reduction potentials in water were also measured using pulse radiolysis. The redox potential is strongly influenced by the nature of the solvent and the solvent sensitivity increases with charge localization. The present results have been used to evaluate solvent effects in view of the Kamlet-Taft relationship. The Kamlet-Taft expression quantitatively describes the solvent effects on the redox properties of 1-3 and gives the relative importance of the different solvent properties. The dominating contribution to the solvent effects is the solvent dipolarity/polarizability pi*, whereas alpha appears to be of minor importance. Furthermore, the relationship between the pi* and reduction potential of radical cations of 1-3 appear to be linear. It was also possible to find the same trend between the solvent dipole moment and peak potential of 1-3. These facts indicate that the nature of solvation is mainly nonspecific.     

HF in clusters of molecular hydrogen. I. Size evolution of quantum solvation by parahydrogen molecules

We present a theoretical study of the quantum solvation of the HF molecule by a small number of parahydrogen molecules, having n = 1-13 solvent particles. The minimum-energy cluster structures determined for n = 1-12 have all of the H(2) molecules in the first solvent shell. The first solvent shell closes at n = 12 and its geometry is icosahedral, with the HF molecule at the center. The quantum-mechanical ground-state properties of the clusters are calculated exactly using the diffusion Monte Carlo method. The zero-point energy of (p-H(2))(n)HF clusters is unusually large, amounting to 86% of the potential well depth for n > 7. The radial probability distribution functions (PDFs) confirm that the first solvent shell is complete for n = 12, and that the 13th p-H(2) molecule begins to fill the second solvent shell. The p-H(2) molecules execute large-amplitude motions and are highly mobile, making the solvent cage exceptionally fluxional. The anisotropy of the solvent, very pronounced for small clusters, decreases rapidly with increasing n, so that for n approximately 8-9 the solvent environment is practically isotropic. The analysis of the pair angular PDF reveals that for a given n, the parahydrogen solvent density around the HF is modulated in a pattern which clearly reflects the lowest-energy cluster configuration. The rigidity of the solvent clusters displays an interesting size dependence, increasing from n = 6 to 9, becoming floppier for n = 10, and increasing again up to n = 12, as the solvent shell is filled. The rigidity of the solvent cage appears to reach its maximum for n = 12, the point at which the first solvent shell is closed.     

溶剂萃取GC-MS法测定纺织衣物中的异味物

采用溶剂萃取法提取纺织品中的土腥霉味化合物二甲萘炕醇(GSM)、2-异丁基-3.甲氧基吡嗪(IBMP)和2-甲基异茨醇(MIB),用气相色谱-质谱法测定其含量.考察了溶剂二氯甲烷和正己烷的提取效果以及提取时间、温度、溶盐因素对提取回收率的影响.结果表明:正己烷的提取效果优于二氯甲烷,采用正己烷提取剂.温度控制在60-8...     

Surveying implicit solvent models for estimating small molecule absolute hydration free energies

Implicit solvent models are powerful tools in accounting for the aqueous environment at a fraction of the computational expense of explicit solvent representations. Here, we compare the ability of common implicit solvent models (TC, OBC, OBC2, GBMV, GBMV2, GBSW, GBSW/MS, GBSW/MS2 and FACTS) to reproduce experimental absolute hydration free energies for a series of 499 small neutral molecules that are modeled using AMBER/GAFF parameters and AM1-BCC charges. Given optimized surface tension coefficients for scaling the surface area term in the nonpolar contribution, most implicit solvent models demonstrate reasonable agreement with extensive explicit solvent simulations (average difference 1.0-1.7 kcal/mol and R(2)=0.81-0.91) and with experimental hydration free energies (average unsigned errors=1.1-1.4 kcal/mol and R(2)=0.66-0.81). Chemical classes of compounds are identified that need further optimization of their ligand force field parameters and others that require improvement in the physical parameters of the implicit solvent models themselves. More sophisticated nonpolar models are also likely necessary to more effectively represent the underlying physics of solvation and take the quality of hydration free energies estimated from implicit solvent models to the next level.     

To gel or not to gel: A prior prediction of gelation in solvent mixtures

The gelation behaviours of low molecular weight gelators 1,3:2,5:4,6-tris(3,4-dichlorobenzylidene)-D-mannitol(G1)and 2,4-(3,4-dichlorobenzylidene)-N-(3-aminopropyl)-D-gluconamide(G2)in 34 solvents have been studied.We found that sample dissolved at low concentrations may become a gel or precipitate at higher concentrations.The Hansen solubility parameters(HSPs)and a Teas plot were employed to correlate the gelation behaviours with solvent properties,but with no success if the concentration of the tests was not maintained constant.Instead,on the basis of the gelation results obtained for the G1 and G2 in single solvents,we studied the gelation behaviours of G1 and G2 in 23 solvent mixtures and found that the tendency of a gelator to form a gel in mixed solvents is strongly correlated with its gelation behaviours in good solvents.If the gelation occurs in a good solvent at higher concentrations,it will take place as well in a mixed solvent(the good solvent plus a poor solvent)at a certain volume ratio.In contrast,if the gelator forms a precipitate in a good solvent at higher concentrations,no gelation is to be observed in the mixed solvents.A gelation rule for mixed solvents is thus proposed,which may facilitate decision making with regard to solvent selection for gel formation in the solvent mixtures in practical applications.     

Electronic properties and ultraviolet absorption and fluorescence spectra of 2-pyridinamine

The u.v. absorption and fluorescence spectra of 2-pyridinamine, its methyl derivatives and its carboxylate salts were measured in various solvents (isooctane, methylcyclohexane and isopentane mixed solvent, ethanol and isooctane mixed solvent, acetic acid and isooctane mixed solvent, and pH adjusted solvent) at room temperature and 77 K. These spectral data were interpretated by the molecular orbital method. From these results it was found that the formation of 2(1H)-pyridinimine with the accompanying 2-pyridinium amine occurs only in the π,π* excited singlet state in the acetic acid and isooctane mixed solvent. On the other hand, the fluorescence spectrum of 2-pyridinamine in the pH ⪢ 11 controlled solution was assigned to the monoanion species, that is, the 2-pyridylamide ion which was formed in the first π,π* excited singlet state.     

Photochemistry of tetramethyl-4-pyrone in alcohol solvents

Irradiation of tetramethyl-4-pyrone in alcohol solvents leads to the formation of tetramethyl-2-pyrone and to a variety of cyclopent-2-enone and cyclopent-3-enone solvent adducts. The structure and mode of product formation is consistent with photochemical generation of a short-lived 2,6-bridged oxabicyclohexenyl zwitterion which undergoes sigmatropic rearrangement to a longer-lived epoxycyclopentenone. Although the zwitterion is efficiently trapped by methanol solvent, in less nucleophilic alcohol solvents it rearranges to the epoxycyclopentenone which isomerizes to the 2-pyrone or reacts with the alcohol solvent to form the observed solvent adducts.     

Excited state solvation dynamics of 2-anilinonaphthalene

Nanosecond fluorescence spectroscopy has been used to study the interaction of 2-anilinonaphthalene with polar solvent molecules which is shown to result in stoichiometric complex formation at low polar solvent concentrations. This is followed by reorientation of the solvent cage when the concentration of polar solvent is high.     

The solvent effect on a styryl-bodipy derivative functioning as an AND molecular logic gate

We study via DFT and TDDFT calculations the photophysical processes of a styryl-bodipy derivative, ( 1 ), of its monometallic complexes 1-M ²⁺ (M = Ca, Zn, and Hg), and its trimetallic complex ( 2 ) unprotonated, protonated and complexed with water molecules in water solvent and in acidic conditions. The main targets of this study are to gain information regarding published reports on fluorophore species mentioning that fluorescent switching results from trace water, to study how 1 behaves in water solvent which is a common used solvent for molecular logic gates (MLG), and how it behaves in acidic conditions. We conclude that in water solvent, as in acetonitrile solvent (which was found before both theoretically and experimentally) there will be a quenching of emission spectra in 1 and 1-M ²⁺ and a retaining of emission in 2 . However, contrary to acetonitrile solvent, in water, a weak peak will be observed for 1 and 1-M ²⁺ , due to a small ratio of reversible protonation, showing that in acetonitrile 1 acts as a better MLG candidate than in water solvent. On the other hand, in acidic conditions all five species will emit and as a result, 1 will not be an AND MLG, showing that the selection of the solvent conditions is crucial for a species to act as an MLG candidate. Finally, we conclude that the retaining of emission is accomplished by the simultaneous tetrahedral geometry of all three aniline N atoms.     

Enhanced CO2 solubility in hybrid MCM-41: molecular simulations and experiments

Grand canonical Monte Carlo simulations are performed in a hybrid adsorbent model in order to interpret the CO(2) solubility behavior. The hybrid adsorbent is prepared by confining a physical solvent (OMCTS) into the pores of a mimetic MCM-41 solid support. As a result, simulated adsorption isotherms of CO(2) nicely match the experimental data for three distinctive systems: bulk solvent, raw MCM-41, and hybrid MCM-41. The microscopic mechanisms underlying the apparition of enhanced solubility are then clearly identified. In fact, the presence of solvent molecules favors the layering of CO(2) molecules within the pores; therefore, the CO(2) solubility in the hybrid adsorbent markedly increases in comparison to that found in the raw adsorbent as well as in the bulk solvent. In addition, a good understanding of confined solvents' properties and solid surface structures is essential to fully evaluate the efficiency of hybrid adsorbents in capturing CO(2). The sorbent-solid interactions along with the solvent molecular size's impact on CO(2) solubility are therefore investigated in this study. We found that an ideal hybrid system should possess a weak solvent-solid interaction but a strong solvent-CO(2) interaction. Besides, an optimal solvent size is obtained for the enhanced CO(2) solubility in the hybrid system. According to the simulation results, the solvent layer builds pseudomicropores inside the mesoporous MCM-41, enabling more CO(2) molecules to be absorbed under the greater influence of spatial confinement and surface interaction. In addition, the molecular sieving effect is clearly observed in the case of larger solvent molecular sizes.     

N-甲基-1-甲硫基-2-硝基乙烯胺的合成新工艺研究

雷尼替丁(Ranitidine)为一种选择性的H2受体拮抗剂,能有效抑制组胺、五肽胃泌素及食物刺激后引起的胃酸分泌,降低胃酸和胃酶的活性,且对胃泌素及性激素的分泌无影响。主要用于治疗十二指肠溃疡、良性胃溃疡、术后溃疡、反流性食管炎及卓-艾综合症等[1]。N-甲基-1-甲硫基-2-硝基     

Solvent vapor annealing of block copolymer thin films: removal of processing history

The ordering processes of PS-b-P2VP block copolymer thin films with different processing histories were studied during solvent vapor annealing by in situ grazing incidence small-angle X-ray scattering (GISAXS). We compared cylinder-forming PS-b-P2VP thin films with 34 kg/mol molecular weight that were prepared in three different ways: spin coating, spin coating and subsequent solvent vapor annealing where the solvent vapor was removed instantaneously, and spin coating and subsequent solvent vapor annealing where the solvent vapor was removed slowly. Block copolymer thin films retained the morphology resulting from the different “processing histories” at smaller swelling ratios. This processing history was erased when the samples reached a higher swelling ratio (~1.4). After the solvent was slowly removed from the swollen film, the surface morphology was characterized by ex situ AFM. All samples showed the same morphology after solvent annealing regardless of the initial morphology, indicating the morphology of solvent annealed samples is determined by the polymer concentration in the swollen film and the solvent vapor removal rate, but not the processing history.     

Competition and coadsorption of di-acids and carboxylic acid solvents on HOPG

The self-assemblies of di-acids HOOC-(CH(2))(n)-COOH (n = 20, 18, 16, 14, 12, 10) in three solvents hexanoic acid, octanoic acid, and decanoic acid on highly oriented pyrolytic graphite (HOPG) were studied with scanning tunneling microscopy (STM). In the solvent hexanoic acid, solvent molecules coadsorb with HOOC-(CH(2))(n)-COOH (n = 20, 18, 16) via formation of hydrogen bonds. The solvent octanoic acid coadsorbs with HOOC-(CH(2))(n)-COOH (n = 20, 18). Decanoic acid only coadsorbs with HOOC-(CH(2))(20)-COOH. In each solvent, the trend of coadsorption between solvent molecules and di-acid molecules decreases with decreasing chain-length of di-acid molecules. These systematic investigations suggest that coadsorption of solvent molecules with di-acid solute molecules is mainly dependent on the relative hydrogen-bond densities in the formed monolayer. This is consistent with the maximization of adsorption heat of the self-assembled monolayers of di-acids dissolved in solvents of carboxylic acids.     

混合溶剂作淋洗剂的体积排除色谱(SEC)中溶剂化高分子峰和溶剂峰的关系

以混合溶剂作淋洗剂的体积排除色谱(SEC)中高分子样品一般会出现2个峰, 分别是溶剂化高分子峰和自由溶剂峰. 理论分析结果表明, 溶剂化高分子峰面积( A3eff )是“裸高分子”峰面积(A3)和被束缚溶剂峰面积(A1*)的加和, 被束缚溶剂峰面积(A1*)和自由溶剂峰面积(A2*)大小相等符号相反. 以聚苯乙烯(3)-氯仿(1)-甲醇(2)体系为研究对象, 分别对A3eff, A3及A2*进行了实验测定, 证实了理论推断的正确性, 表明由高分子峰和由溶剂峰来求算优先吸附系数是等价的.     

Chemical reaction in binary mixtures near the critical region: thermal decomposition of 2,2'-azobis(isobutyronitrile) in CO2/ethanol

The effects of pressure and of the composition of the CO2/ethanol mixed solvent in the critical region on the kinetics of the decomposition of 2,2'-azobis(isobutyronitrile) (AIBN) were studied at 333.15 K. The rate constants (kd) in the mixed solvent far from the critical point and in liquid n-hexane and ethanol were also determined for comparison. It was found that kd is very sensitive to pressure in the mixed solvent near the critical point. However, in the mixed solvent outside the critical region kd is nearly independent of pressure. Interestingly, kd in the mixed solvent in the critical region can be higher than that in ethanol at the same temperature, suggesting that no significant enhancement in the reaction rate by a small pressure change in the critical region of the mixed solvent can be achieved by changing the composition of the liquid solvent in the traditional way. Transition-state theory can predict kd in the mixed solvent far from the critical point and in the liquid solvents well. However, it cannot predict kd in the mixed solvent in the critical region. The special intermolecular interaction between the solvent and the reaction species may contribute to this interesting phenomenon. This work also shows that if pure CO2 or ethanol are used as solvents, the reaction cannot be carried out in the critical region of the solvents at the desired temperature, while it can be conducted in the critical region of the mixed solvent of suitable composition, where the solvent is highly compressible.     

Demixing effects in thin-layer chromatography with NH2-modified silica gel precoated plates

Summary Demixing effects in thin-layer chromatography have been investigated with NH₂-modified silica gel precoated plates and for frequently used hydroorganic binary solvents of various compositions with salt addition.The position of the solvent demixing front depends on: (1) solvent composition, (2) nature of the organic modifier and (3) salt concentration. Whatever the organic modifier, for a given water percentage in the developing solvent, solvent demixing is found to occur at the same concentration of NaCl.     

PVT properties of di-(2-ethyl hexyl) phosphoric acid

Di-(2-ethyl hexyl) phosphoric acid (hereafter referred as D2EHPA) is an important solvent for solvent extraction industry. It is also used in nuclear solvent extraction as a solvent for TALSPEAK and REVERSED TALSPEAK processes for actinide (III)–lanthanide (III) separation. Its PVT properties are not available in literature. In this work, group-contribution approach was used to predict its PVT properties as well as selected physical properties like normal boiling point.