ZnCl2催化木质素磺酸盐加氢液化的溶剂效应

选用ZnCl₂为催化剂在高压反应釜中进行加氢液化反应,利用GC-MS和红外光谱技术,研究溶剂极性及供氢能力对木质素磺酸盐液化产率及产物的影响。产率分析表明,极性溶剂有利于木质素液化转化,供氢溶剂有利于提高轻馏分产率,水溶剂条件下木质素液化转化率最高,甲醇溶剂体系条件下轻馏分产率最高,相对最低液化转化率及轻馏分产率的1,4二氧六环溶剂体系分别提高2.0倍和1.9倍。GC-MS分析表明,中等极性溶剂有利于中间产物溶解稳定,供氢溶剂四氢萘通过释放氢自由基结合稳定中间产物。乙醇溶剂条件下中间产物相对含量是48.76%,相对最低含量水溶剂体系提高2.2倍。红外光谱分析表明,醇类溶剂参与反应,焦油产物羟基峰强度增强。     

不同醇类对磷钨酸催化超临界醇解液化木屑的影响

以可溶解于醇类的磷钨酸为催化剂,在超临界醇体系下液化木屑,探讨甲醇、乙醇、正丙醇、异丙醇等不同醇类溶剂对木屑醇解液化的影响,同时采用FT-IR和GC-MS等对液化产物进行了表征分析。结果表明,反应压力和溶剂的极性大小对木屑的液化效率以及液化产物影响显著。甲醇、乙醇、正丙醇、异丙醇反应体系的液化率和主要液化产物酯类化合物的含量比率,分别为54.75%和43.759%、90.29%和23.531%、85.90%和41.761%、89.15%和28.619%,特别在甲醇体系中,乙酰丙酸甲酯的含量高达33.374%;在异丙醇体系中酚类化合物可达到24.342%;醛类化合物只出现在甲醇体系中。在正丙醇体系中没有酚类产物,表明极性最小的正丙醇,提供很少的H*,更不容易将木质素降解。     

唑烷酮类化合物的光合成研究

通过光化学方法取代传统的金属催化等法合成重要的药物中间体唑烷酮,反应条件温和、操作简便、产率较高且污染少.同时研究了丙酮、甲醇、乙腈3种溶剂与水的不同配比对反应产物的影响.随着溶剂极性增加,立体选择性有一定提高.     

Reaction of phthaloylasparic anhydride with o-phenylenediamine in solution and spectral analysis of the reaction products

The ring-opening addition reaction of phthaloylasparic anhydride (I) with o-phenylenediamine (II) in a solution is affected by the polarity of the solvent used. At the molar ratio of 1:1, I and II undergo a β-oriented ring-opening reaction in polar solvents, such as DMF, DMAC, and DMSO; while in weaker polar solvents, such as dioxane and tetrahydrofuran, α-orientation predominates. By heating in a solvent mixture of DMF and xylene, the ring-opening products undergo condensation, and are converted into two isomers. One is methanol soluble 3-phthalimido-3-(2)benzimidazolylpropanoic acid (V) resulting from the α-oriented ring-opening reaction, the other is the sparingly soluble (in DMF) 2-phthalimido-3-(2)benzimidazolylpropanoic acid (VI) resulting from the β-oriented ring-opening reaction. The soluble V can be precipitated as cotton-like crystals from methanol and chloroform. When treated with acetic anhydride, V and VI are converted to other isomers, namely 3-phthalimidobenzimidazopyrrolone (VII) and 2-phthalimidobenzimidazopyrrolone (VIII). The isomers were identified by spectral analysis.     

铌酸催化的苯甲醛与甲醇缩合反应

采用铌酸为催化剂,探索了该催化剂对苯甲醛与甲醇缩合反应的影响.优化反应条件是,催化剂用量为反应物质的量的5mol%,甲醇10mL(兼作溶剂),回流状态下反应2h,反应的产率和转化率分别达到94%、98.0%.该催化剂同样适用于其他醛(酮)与甲醇的缩合反应,可得到34%～89%的产率.所述方法操作简单、产率高、选择性好而且对环境友好,反应结束后,催化剂很容易回收,并能有效重复使用.     

Tautomeric equilibrium of ethyl acetoacetate in compressed CO2 + ethanol and CO2 + methanol mixtures

Tautomerism equilibrium of ethyl acetoacetate (EAA) in compressed CO2 + methanol and CO2 + ethanol mixtures was studied by UV-Vis spectroscopy at 308.15 K and different pressures. The volume expansion coefficient (alpha) of the solvents at different pressures was also determined. The relative permittivity (epsilon) of CO2 + methanol and CO2 + ethanol mixtures at different conditions was calculated using the Kc and Onsager solvent parameter. The equilibrium constant (Kc) of EAA in the binary mixtures increases considerably with increasing pressure or volume expansion coefficient. The relative permittivity or the polarity of the binary mixtures decreases sharply with increasing volume expansion coefficient in the range of 0 < alpha < 1.5. However, as the volume expansion coefficient exceeds 1.5, the relative permittivity decreases slowly. In other words, the dissolution of CO2 in the polar solvents can reduce the polarity of the solvents significantly in the low volume expansion coefficient range, and the polarity of the solution is not sensitive to the volume expansion coefficient as its value is large enough. The difference in polarity of the two solvents reduces with increasing pressure and becomes negligible after volume expansion coefficient exceeds about 2.5.     

Electrochemical polymerization of dicarboxylic acids—IV. Polymerization of sebacic acid

The electrolysis of sebacic acid was investigated in methanol, methanol:pyridine (1:1) and methanol:acetonitrile (1:1). The various products were analyzed. In methanol, the major product was the oligomeric carboxylic acid fraction (55%) and the yield of oligomeric hydrocarbons and polymer was lower. With the other two solvents, the polymer was the major product. Four types of hydrocarbons were formed: n-alkane, 1-alkene, x-alkene (the position of the double bond is not known) and cycloalkane. The polymers obtained in all the solvents had the character of cross-linked and branched polyethylene, having ester and methoxy groups. These polymers did not suffer degradation during basic hydrolysis. In comparison with adipic acid, sebacic acid had more tendency to yield polymer and carboxylic acids than hydrocarbons.     

Exciplex and radical ion intermediates in the photochemical reaction of 9-cyanophenanthrene with 2,3-dimethyl-2-butene

The photochemical reaction of 9-cyanophenanthrene and 2,3-dimethyl-2-butene, first reported by Mizuno, Pac and Sakurai, has been reinvestigated. The formation of a [2+2]-cycloadduct via a singlet exciplex is the exclusive reaction in the nonpolar solvents benzene and ethyl acetate. Photochemical behavior in polar solvents is far more complicated than previously reported. Mechanisms consistent with the effects of solvent polarity, methanol concentration, methanol deuteration, and light intensity upon product yields are proposed. Formation of a 9-cyanophenthrene anion radical and 2,3-dimethyl-2-butene cation radical is the primary photoinitiated process in polar solvent. The cation radical can undergo deprotonation to yield an allyl radical or nucleophilic attack by methanol to yield a methoxyalkyl radical. Covalent bonding of these radicals and the 9-cyanophenanthrene anion radical gives rise to the acyclic adducts obtained in polar solvents. The anion radical can also be protonated, leading ultimately to the formation of 9,10-dihydro-9-cyanophenanthrene.     

Photoionization versus photoheterolysis of all-trans-retinol. The effects of solvent and laser radiation intensity

The time-resolved formation of the retinyl carbocation from all-trans-retinol and all-trans-retinol acetate was studied by use of picosecond flash photolysis. From both precursors, the retinyl cation is produced by heterolytic C-O bond cleavage in solvents of medium polarity (acetonitrile, tetrahydrofuran, propanol with Reichardt polarity parameter ET(N) approximately 0.5) and high polarity (EtOH, MeOH, TFE, HFIP, ET(N) > 0.6) during the laser pulse (< or =5 ps) where its lifetime is >10 ns. The absorption maximum of the cation at early times (t < 100 ps) is at lambda = 590-600 nm; it shifts to shorter wavelengths (Deltalambda = 5-10 nm) within 1-10 ns. This spectral shift is suggested to be due to contact ion pair --> solvent-separated ion pair --> free-ion transformation. The quantum yield of cation formation phi(cat) is independent of excitation wavelength (213, 266 or 355 nm). Photoheterolysis proceeds via a one-quantum process. In chlorinated solvents, i.e. n-BuCl, 1,2-dichloroethane, chloroform or CCl(4), formation of the retinol radical cation (which is characterized by a peak at 610 nm and further absorption maxima at approximately 840 and approximately 940 nm) by intermolecular electron transfer to the solvent molecules was detected. The radical cation lifetime in all these solvents is 1.5-2 ns, except for CCl(4) where it is 0.25 ns. The formation of the radical cation or cation was not detected in the low polarity solvents: cyclohexane, hexane, dioxane and p-xylene. However, in solvents of medium and high polarity, at high radiation intensities the radical cation may form in addition to the cation (as a result of two-quantum ionization). DFT calculations confirm our experimental results. The rate of retinol S(1) depopulation (k = 0.3-1 x 10(9) s(-1)) is almost independent of the solvent polarity in the range from cyclohexane to methanol. In highly polar solvents (ET(N) > 0.9) the rate increases to (0.5-5) x 10(10) s(-1).     

Preparation of 1-(4-nitrophenyl)-2-formylpyrrole from furfural

The products of the condensation of furfural with p-nitroaniline in an acidic medium in various solvents were investigated. It was established that the well-known method gives 1-(4-nitrophenyl)-2-formylpyrrole in no higher than 55% yield and 2,3-bis(4-nitrophenylamino)-2-formylpyrrole in 27% yield. A method based on a previously described method is recommended (the products are obtained in up to 72% yields).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1062–1066, August, 1981.     

合成分枝型聚乙二醇的简便新方法

以赖氨酸和mPEG5000为起始物,利用多肽合成中常用的保护、缩合和脱保护等方法合成了在生物医学领域中具有重要应用价值的分枝型聚乙二醇.用该方法形成的分枝型PEG在有机相中以缩合反应的方式一步完成,反应条件温和,且有较高的产率(61%).各步产物的表征都与其结构一致.最终产物分枝型PEG的¹HNMR的表征结果与其结构吻合.     

Determination of poly(ethylene glycol)s by both normal-phase and reversed-phase modes of high-performance liquid chromatography

A normal-phase HPLC system using an amino column has been developed to characterise oligomers of poly(ethylene glycol)s (PEGs) of average M_r 400 to 2000 with derivatisation by dinitrobenzoate. Normal-phase HPLC with gradient elution using ternary solvents of hexane, dichloromethane and methanol has produced a baseline resolution for oligomers of PEG 400, 600 and 1000, while PEG 1000 and 2000 were analysed by using binary solvents of acetonitrile and water. Mixtures of PEGs have been determined by these HPLC systems. PEG 400 in a textile finish has also been determined with satisfactory recovery. It has been found that the hydroxyl group of solvents in normal-phase HPLC plays an important role in resolution and retention of PEG oligomers. Derivatisation efficiency for PEGs by dinitrobenzoyl chloride and quantitative determination of derivatised PEGs by HPLC have been studied. A reversed-phase (RP) mode of HPLC was examined for determination of PEG 400 oligomers. The normal-phase system provided greater resolution for oligomers of PEGs.     

THE EFFECT OF MEDIUM POLARITY ON THE HEMATOPORPHYRIN-SENSITIZED PHOTOOXIDATION OF l-TRYPTOPHAN

Abstract The 83 μM hematoporphyrin (HP)-sensitized photooxidation of 0.1 mM tryptophan in aqueous solution buffered at pH 7.4 or in binary mixtures of phosphate buffer and organic solvents of higher (formamide) or lower (N,N-dimethylformamide, methanol, ethanol, tetrahydrofuran) polarity proceeds by a pure singlet oxygen (¹O₂) mechanism as suggested by azide quenching experiments, the rate-enhancing action of deuterated solvents, and the lack of any significant reaction between triplet HP and tryptophan. Both the first-order rate constant of the photoprocess and the photooxidation quantum yield (φ= 0.011 in phosphate buffer at pH 7.4) increase when the medium polarity is increased (e.g. φ= 0.024 in 90% formamide); this results mainly from the greater quantum yield of ¹O₂ generation and the longer lifetime of ¹O₂. The intrinsic reactivity of ¹O₂ with tryptophan is independent of formamide concentration. A moderate decrease in the medium polarity (e.g. in the range 0-30% methanol) enhances the efficiency of tryptophan photooxidation (φ= 0.014 in 30% methanol) as a result of the enhanced quantum yields of triplet HP and ¹O₂ formation. In contrast, the overall photooxidation rate is depressed at high concentrations of low-polarity organic solvents (e.g. φ= 0.0039 in 90% methanol) due to a 5.5-fold drop of the rate constant for the ¹O₂-tryptophan reaction which counteracts the enhancement of the lifetime and quantum yield of triplet HP and ¹O₂. The solvent composition also affects the equilibria between monomeric and multimeric forms of HP. However, under our experimental conditions, the aggregation state of HP appears to exert only a minor influence on the efficiency of tryptophan photooxidation.     

Spectrochemical Properties of Noncubical Transition Metal Complexes in Solutions. XV. Solution Properties of bis(Salicylideneaniline)Copper(II)

The complex obtained by condensation of salicylideneaniline with copper(II) acetate was studied in a variety of solvents. This deep-brown crystalline compound is soluble in common solvents, such as, chloroform, toluene, dioxane, methanol, ethanol, dimethyl formamide, dimethyl sulfoxide, and acetonitrile—a necessary condition for observing solvatochromism. The complex has been characterized by elemental analysis, molar conductivity, EPR, and ultraviolet (UV) and visible (VIS) spectroscopy. The available X-ray data shows planar coordination geometry for the copper center. Combined multi-technique experiments have been applied to confirm the structure of the complex in solution. The molar conductivities indicate nonelectrolytic properties. EPR measurements preclude the possibility of solvent coordination at the axial positions of the complex. Spectroscopic measurements were used to study the coordination properties of donor atoms and their bonding ability, as well as trichromaticity coordinate calculations. The results obtained show that the interactions of metal with donors depend on donor strength and polarity of solvent.     

在交联聚合物微球GMA/MMA表面接枝固载聚乙二醇的研究

以乙二醇二甲基丙烯酸酯为交联剂,采用悬浮聚合方法,制备了甲基丙烯酸缩水甘油酯(GMA)和甲基丙烯酸甲酯(MMA)的交联微球GMA/MMA.使用Lewis酸催化剂,通过环氧键的开环反应,将聚乙二醇(PEG)偶合接枝在交联微球GMA/MMA表面,实现了PEG的固载化,制得了三相相转移催化剂PEG-GMA/MMA.重点考察了各种因素对PEG接枝固载过程的影响,并研究了反应机理.实验结果表明,以交联微球GMA/MMA为载体,可以顺利地实现PEG的固载化,这是制备PEG三相相转移催化剂的简捷途径.实验发现,Lewis酸也能催化环氧键的开环反应,而且比质子酸的催化更加有效.溶剂的极性对偶合接枝反应的影响较大,采用极性大的溶剂有利于PEG的接枝固载.偶合接枝体系中,过高的催化剂用量会导致PEG双端羟基参与接枝反应,使载体表面大分子之间发生附加交联,不利于PEG的接枝固载.在适宜的反应条件下,接枝微球PEG-GMA/MMA表面的PEG接枝度可达0.20 g/g.     

THE EFFECT OF SOLVENT POLARITY ON THE CONDENSATION OF HYDROLYZED TETRAETHYLORTHOSILICATE IN MICROEMULSION GELS

A study of the condensation of hydrolyzed tertaethylorthosilicate (TEOS) was conducted to investigate the influence of solvent polarity. A non-aqueous microemulsion was formed to which was added water (pH 1) and TEOS. The various condensation products were observed with ²9Si NMR of systems of differing amounts of formamide and decanol/decane at increasing time intervals. The solvent polarity of the solvent system was found to clearly influence the initial and final rates of condensation, despite the fact that the specific condensed moieties were the same in each of the systems studied.     

Absorption and emission spectroscopic characterisation of 8-amino-riboflavin

The flavin dye 8-amino-8-demethyl-d-riboflavin (AF) in the solvents water, DMSO, methanol, and chloroform/DMSO was studied by absorption and fluorescence spectroscopy. The first absorption band is red-shifted compared to riboflavin, and blue-shifted compared to roseoflavin (8-dimethylamino-8-demethyl-D-riboflavin). The fluorescence quantum yield of AF in the studied solvents varies between 20% and 50%. The fluorescence lifetimes were found to be in the 2–5 ns range. AF is well soluble in DMSO, weakly soluble in water and methanol, and practically insoluble in chloroform. The limited solubility causes AF aggregation, which was seen in differences between measured absorption spectra and fluorescence excitation spectra. Light scattering in the dye absorption region is discussed and approximate absorption cross-section spectra are determined from the combined measurement of transmission and fluorescence excitation spectra. The photo-stability of AF was studied by prolonged light exposure. The photo-degradation routes of AF are discussed.     

Intramolecular photoarylation of alkenes by phenyl cations

Acetone-sensitized irradiation of various o-chlorophenyl allyl ethers in polar solvents led to either (dihydro)benzofurans or chromanes. The reaction appeared to involve photoheterolysis of the aryl-Cl bond followed by phenyl cation addition onto the tethered double bond either in 5-exo or 6-endo modes. The adduct cation gave the end products by deprotonation; addition of chloride anion or of the solvent, depending on the structure; and the conditions used. Preference for the 5-exo mode increased in passing from medium polarity (methylene chloride, ethyl acetate) to high polarity solvents (aqueous acetonitrile, methanol, 2,2,2-trifluoroethanol), for which this was often the exclusive path. The same compounds underwent photohomolysis when irradiated in cyclohexane, and radical cyclization was one of the process occurring. Substitution of a methylene group for the ether oxygen atom made 6-endo cyclization by far the main path in a related o-chlorophenylbutene. Again, the selectivity was higher in polar protic solvents. The results are discussed in terms of in cage ion pair versus free phenyl cation reactions.     

Effect of the composition of aqueous-organic mixtures on the sensitivity of thermal lens measurements

Thermooptical properties of aqueous solutions of methanol, acetonitrile, dimethyl sulfoxide, ethylene glycol, glycerol, 1,4-dioxane, and sucrose were studied, and it was found that the analytical thermal lens signal depends on the nature of the organic component, most of all, on the polarity and molecular size. The sensitivity coefficient of thermal lens measurements is increased to a maximum extent in methanol solutions (by 7.3 times at the concentration 50 vol %) and acetonitrile (by 8.8 times at 26 vol %). It was found that a small concentration of water slightly affects the thermooptical properties of polar organic solvents.     

疏水作用对光化学和光物理过程的影响 Ⅻ.2-羟基-4-烷氧基二苯甲酮在不良溶剂中的簇集

测定了2-羟基-4-甲氧基二苯甲酮(HMDB)和2-羟基-4-辛氧基二苯甲酮(HODB)在良溶剂和不良溶剂中的吸收光谱。在不良溶剂(乙二醇-水的混合溶剂)中,带长链的HODB发生簇集。由于簇集体内极性较小,HODB的吸收光谱与其在环己烷中相似。HMDB不发生簇集。