Empirical Polarity Parameters of Celluloses and Related Materials

Kamlet–Taft's (hydrogen-bond donating (HBD) ability), (hydrogen-bond accepting (HBA) ability), and * (dipolarity/polarizability) parameters of native cellulose batches, carboxymethyl celluloses (CMCs), cellulose tosylates (CTs), and other derivatives with different degree of substitution (DS), chitine, amylose, amylopectine, and cellobiose are presented. Fe(phen)₂(CN)₂ [cis-dicyano-bis-(1,10)-phenanthroline-iron(II), (1)], Michler's ketone [bis-4,4-(N,N-dimethylamino)benzophenone, (2)], 4-aminobenzophenone (3), coumarine 153 (4), and Reichardt's dye (5) were used as solvatochromic surface polarity indicators. The UV/Vis reflectance spectra of the five surface polarity indicators 1, 2, 3, 4, and 5, adsorbed on the samples from the organic solvents, were measured and the absorption maxima were used to calculate the , , *, and E _T(30) values of the polysaccharides surface. , , and * depending on degree of crystallinity of the cellulose samples have been determined. depends on both amount and strength of accessible acidic surface groups on the cellulose surface. It is significantly larger for crystalline sections than for amorphous parts. The * scale is suitable for the classification of different cellulose batches, because it seems to be independent of inhomogeneities of the cellulose surface. The -values of CMCs and CTs significantly decrease with increasing DS inasmuch the number of cellulosic-OH groups (Cell-OH) decreases. A slight increase of * with DS is observed for CTs.     

配位化学中的直线自由能关系(XIX)

前文[1]曾报导了侧基二氧四胺大环配体的合成及表征．与普通配合物相比，大环多胺配合物具有较高的稳定性及惰性和奇特的空间构型，其过渡金属配合物具有特殊的性质和用途，如作酶的模型、氧的载体等．铜（Ⅱ）配合物可作超氧歧化酶（SOD）的模型，超氧离子是人体内的氧代谢产物，它在体内过量积累会引起多种疾病，超氧歧化酶对超氧离子起催化歧化作用，以维持机体的正常运行间，故这种大环多胺Cu（Ⅱ）配合物具有重要的生物功能及广阔的应用前景．本文研究了四种带侧基二氧四胺大环配体-5-取代邻菲罗啉（5－Xphen；L1）铜（Ⅱ）三元配合…     

Effects of Hydrogen-bonding Interaction and Polarity on Emission Spectrum of Naphthalene-Triethylamine in Mixed Solvent

The effects of the protic and aprotic polar solvents on the emission spectrum of the naphthalene-triethyl-amine system in THF were studied under conditions of steady-state illumination. The fluorescence spectrum of the naphthalene-triethylamine system consists of two emission bands, the fluorescence band of naphthalene (band A, 329 nm) and the emission band of the exciplex(band B, 468 nm). The intensities of both the emission bands decrease with increasing the solvent polarity. The intensity of band B also decreases due to the hy-drogen-bonding interaction between triethylamine and protic solvent, while that of band A increases. It is thus suggested that the quenching of naphthalene fluorescence by triethylamine in THF occurs through the charge transfer and electron transfer reactions. The spectral changes upon the increase of solvent polarity can be explained by the dependences of the equilibrium constant between exciplex and ion-pair and the rate constant for the electron transfer reaction from triethyl.amine to the excited naphthalene on the rel.ative permittivity of solvent. It is shown that the formation of intermolecular hydrogen-bonding between triethylamine and protic solvent suppresses the quenching reaction by the decrease in free amine. Acetonitrile has only a polar effect and trichloroacetic acid only a hydrogen-bonding(or protonation) effect, while alcohols have both the effects. The effects of alcohols could be separated into the effects of solvent polarity and intermolecular hy-drogen-bonding interaction quantitatively.     

Linear free energy relationships in the chromium(VI) oxidation of sulfides in acetonitrile

The oxidation of 14 para-, meta-, and ortho-substituted phenyl methyl sulfides with isonicotinium dichromate in acetonitrile, brought out by p-toluenesulfonic acid, follows a common mechanism, conforms to the isokinetic relationship but not to any of the linear free energy relationships; the isokinetic temperature lies in the experimental temperature range.     

Lack of Linear Free Energy Relationships in the p-Toluenesulfonic Acid Mediated Chromium(VI) Oxidation of Organic Sulfides

Summary.  The oxidation of methylphenyl sulfide by imidazolium dichromate in acetonitrile mediated by p-toluenesulfonic acid is first order in IDC and TsOH and zero order in MeSPh in the concentration range studied. The IDC oxidation of 14 para-, meta-, and ortho-substituted phenylmethylsulfides at 20–45°C conforms to the isokinetic relationship but not to any of the linear free energy relationships; the isokinetic temperature lies within the experimental temperature range. Received April 18, 2000. Accepted (revised) July 12, 2000     

On linear free energy correlations in liquid-phase catalytic hydrogenation of aromatic compounds

Application of linear free energy relationships (correlation between kinetics and thermodynamics) to catalytic hydrogenation of aromatic compounds in the liquidphase over supported metal catalysts is discussed.     

Effect of Ionic Liquid on Retention of Solutes on C_(18) Column Based on Linear Solvation Energy Relationships

Several chromatography systems with ionic liquids and a mixture of water with the modifier as mobile phase were characterized via the linear solvation energy relationships(LSER) model. The effects of the ionic liquids and modifier(methanol) concentrations on the retention of 10 solutes(caffeine,pyridine,aniline,phenol,methylparaben,acetopenone,m-cresol,p-cresol,o-cresol,and benzene) were discussed. The LSER model demonstrated high potential to predict retention factors with high squared correlation coeffici...     

气相色谱固定液极性和选择性评价

对非同族化合物溶质在两种固定相上保留值的关系进行了理论推导，并将该方程应用于８９种常见固定相的极性和选择性的评价。固定相的极性可用Ｂ值来评价，而选择性则用Ｂ、Ｔ３＾ａ，Ｃ３β值来评价。用该方程评价固定相具有两个优点，一是基于分子间作用力来评价固定相；二是探针化合物的选择不再受限制。     

The polarity of polyoxyethylene glycol dialkyl ethers and their sulphur analogs as measured by parameters considering intermolecular electric interactions

Summary The new stationary phase polarity parameters B_N and B_S evaluated from the concept of the electric intermolecular interactions are used to describe the polarity of polyoxyethylene glycol dialkyl ethers and their sulphur analogs. Relations between the discussed parameters and accepted measures of surfactants' polarity are presented and discussed. The considered parameters are correlated with the compound structures. Structural increments for characteristic fragments of the molecule are calculated and use to predict B_N and B_S values.     

Effect of Solvent Polarity on Excited-State Double Proton Transfer Process of 1, 5-Dihydroxyanthraquinone

The excited-state double proton transfer (ESDPT) properties of 1, 5-dihydroxyanthraquinone (1, 5-DHAQ) in various solvents were investigated using femtosecond transient absorption spectroscopy and the DFT/TDDFT method. The steady-state fluorescence spectra in toluene, tetrahydrofuran (THF) and acetonitrile (ACN) solvents presented that the solvent polarity has an effect on the position of the ESDPT fluorescence emission peak for the 1, 5-DHAQ system. Transient absorption spectra show that the increasing polarity of the solvent accelerates the rate of excited state dynamics. Calculated potential energy curves analysis further verified the experimental results. The ESDPT barrier decreases gradually with the increase of solvent polarity from toluene, THF to ACN solvent. It is convinced that the increase of solvent polarity can promote the occurrence of the ESDPT dynamic processes for the 1, 5-DHAQ system. This work clarifies the mechanism of the influence of solvent polarity on the ESDPT process of 1, 5-DHAQ, which provides novel ideas for design and synthesis of new hydroxyanthraquinone derivatives.     

基于分子表面静电势参数分析溶剂的极性性质

用理论计算导出的分子表面静电势参数∏和б2tot对一系列溶剂的五种极性指标ETN、π*、Py、SPP和S'进行了相关分析,与Catalan的理论热力学分析结果进行了比较.结果显示:S'是一个适用性很好的溶剂极性参数,而质子性溶剂的ETN值、芳香化合物和多卤代化合物的π*值和SPP值则存在着一定的非极性因素.     

Solvent effect on photochromism of a dithienylperfluorocyclopentene having diethylamino group

Some photochromic diarylethenes having polar substituents were synthesized, and their photochromic behavior was examined. They exhibited photochromism with the similar photoreactivity in a non-polar solvent. However, the photocyclization quantum yield of dithienylperfluorocyclopentene having diethylamino group was found to decrease in polar solvents. The yield in acetonitrile was estimated to be 60 times smaller than that in hexane. The yields determined in various solvents were found to be correlated with the solvent polarity parameter E_T(30). Such an effect was not observed in dithienylfluorocyclopentenes bearing methoxy or acetoxy group and in non-fluorinated dithienylcyclopentene bearing diethylamino group.     

溶剂极性对高效氯氟氰菊酯微乳液相行为及其稳定性的影响

高效氯氟氰菊酯; 微乳液; 极性;荧光探针     

Intramolecular and intermolecular hydrogen-bonding effects on the dipole moments and photophysical properties of some anthraquinone dyes

The present work stems from our interest in the synthesis, characterization and biological evaluation of lanthanide(III) complexes of a class of coumarin based imines which have been prepared by the interaction of hydrated lanthanide(III) chloride with the sodium salts of 3-acetylcoumarin thiosemicarbazone (ACTSZH) and 3-acetylcoumarin semicarbazone (ACSZH) in 1:3 molar ratio using thermal as well as microwave method. Characterization of the ligands as well as the metal complexes have been carried out by elemental analysis, melting point determinations, molecular weight determinations, magnetic moment, molar conductance, IR, (1)H NMR, (13)C NMR, electronic, EPR, X-ray powder diffraction and mass spectral studies. Spectral studies confirm ligands to be monofunctional bidentate and octahedral environment around metal ions. The redox behavior of one of the synthesized metal complex was investigated by cyclic voltammetry. Further, free ligands and their metal complexes have been screened for their antimicrobial as well as DNA cleavage activity. The results of these findings have been presented and discussed.     

Propylene Polymerization Catalyzed by Bis (R3-indenyl) Zirconium Dichloride/Aluminoxane--Synthesis of Metallocenes and Influence of Sol vent Polarity on Poi ymerization

Three unbridged metallocenes, bis(2,4,7-Mea-indenyl)zirconium dichloride (1), bis (2-Me4,7-Etz-indenyl) zirconium dichloride (2) and bis (2,4,6-Me3-indenyl) zirconium dichloride (3)were synthesized. The effect of solvent polarity on propylene polymerization catalyzed by the metallocenes in the presence of methylaluminoxane(MAO) and triisobutylaluminum(TIBA) was investigated in the toluene/CH2Cl2 mixed solvent. Changing the solvent polarity was found to influence the catalytic activity, polymer molecular weight and stereospecificity of the catalysts.The changes in the position of the substituents on the ligand caused the different responses of the catalyst to the changes in solvent polarity. The isotactic stereosequence of polypropylene was found to increase with the increase in the polarity of the reaction medium.     

Contrasting effects of redox potentials on the rate constants of oxidation and hydrolysis reactions in ruthenium complexes

We report in this work the rate constant of oxidation by peroxydisulfate of the ammine ruthenium center in [(bpy)₂Ru(μ-5-CNphen)Ru(NH₃)₅]⁴⁺ (bpy?=?2,2′-bipyridine and 5-CNphen?=?5-cyano-1,10-phenanthroline) and the rate constant of hydrolysis of coordinated acetonitrile in [Ru(TPTZ)(bpy)(CH₃CN)]²⁺ (TPTZ = 2,4,6-tris(2-pyridil)-1,3,5-triazine). With these data and literature values of related reactions, we establish the existence of contrasting effects of redox potentials of Ru^3+/2+ couples on the rates of both processes.     

Basic Alumina as an Efficient Catalyst for Preparation of Semicarbazones in Solvent Free Conditions

An efficient and simple procedure for conversion of different classes of aldehydes and ketones into the corresponding semicarbazones with semicarbazide hydrochloride using basic alumina is studied.     

Definition of Hydration Parameters in the Region of Maximal Solvent Density

The approach to the definition of hydration numbers using the ultraacoustic method is critically discussed. Leaning upon a correct thermodynamic analysis, limited validity is shown of the main equation used in the publication of Onori over a wide range of state parameters. It is revealed that the mentioned equation is true only in the region of maximum solvent density. For this range of conditions, hydration numbers, the compressibility of hydration formations, molar volume and compressibility of water in hydration shells, molar volume and compressibility of stoichiometric mixtures of ions of NaCl are calculated based upon the experimental data of density and speed of ultrasound in solutions.