Protonierung und Solvatation schwacher organischer Basen. IV. H-NMR-spektroskopische Bestimmung der Basizität aliphatischer Ketone

Protonation and Solvation of Weak Organic Bases. IV. ¹H-N.M.R. Spectroscopic Determination of the Basicity of Aliphatic Ketones From protonation ratios for a series of methyl and ethyl alkyl ketones 1—13 with gradually branched alkyl groups in the H₂O–H₂SO₄ system, determined by ¹H-n.m.r. spectroscopy, basicity and solvation parameters are systematically estimated by application of extrapolation procedures based on the Hammett acidity function H₀ or the excess acidity X.     

Physicochemical criteria for reverse osmosis separation of aldehydes,ketones, ethers,esters, and amines in aqueous solutions using porous cellulose acetate membranes

Reverse osmosis separation of 62 different proton acceptor compounds (bases) including 7 aldehydes, 8 ketones, 12 ethers, 11 esters, and 24 amines in aqueous solutions in the concentration range 0.00075 to 0.003 g mole/l. (～100 ppm in most cases) have been studied using porous cellulose acetate membranes at 250 psig. All reverse osmosis data are for single solute systems. Solute separation data for aldehydes, ketones, ethers, and esters are correlated with Δv_s (basicity) (shift in the OD band maximum in the IR spectra of CH₃OD in benzene and other solvents used as solutes in reverse osmosis experiments), and those for the amines are correlated with dissociation constant (given as pK_a) and the degree of dissociation of the molecule. Solute separation increases with increase in Δv_s (basicity) for aldehydes, ketones, ethers, and esters and with increase in degree of dissociation for amines. The separation data and the basicity parameters for the above classes of compounds are also correlated with Taft numbers. The results are consistent with those reported earlier for alcohols, phenols, and monocarboxylic acids in aqueous solutions and show that data on Δv_s (basicity), pK_a, and Taft numbers are valid physicochemical criteria governing reverse osmosis separation of aldehydes, ketones, ethers, esters, and amines.     

Modulation of Pharmacologically Relevant Properties of Piperidine Derivatives by Functional Groups in an Equatorial or Axial β-Position to the Amino Group

Thirteen epimeric pairs of 5-substituted N-piperonyl-3-phenylpiperidine derivatives were synthesized in order to explore the stereospecific modulation of basicity, lipophilicity, aqueous solubility, and membrane permeation by functional groups in equatorial or axial positions beta to the amine unit. While this comprehensive data set provides enhanced insight into multiple factors that affect basicity and lipophilicity, it fills an important knowledge gap, providing a frame of reference for the property-based design of bioactive compounds. Impacts on amine basicity are very pronounced for the β-equatorial functional groups and parallel basicity-lowering effects known for acyclic amine derivatives. For β-axial functional groups, the basicity-lowering effects are generally decreased, with the nitrile group as the only exception. Basicity and lipophilicity modulations observed for β-axial functional groups are quite diverse and rationalized in terms of intramolecular hydrogen bonding, dipolar interactions, and special solvation effects. Aqueous solubility and (artificial) membrane permeability are discussed with reference to lipophilicity.     

The role of hydrogen-bond in solubilizing drugs by ionic liquids: A molecular dynamics and density functional theory study

The solvation mechanisms of aspirin and etomidate in four combinations of [Emim]⁺ and [BuGun]⁺ paired with [OAc]⁻ and [NTf₂]⁻ were systematically studied by molecular dynamics simulations and DFT calculations. It was shown that the favorable solvation of aspirin and etomidate correlated well with hydrogen-bond (H-bond) basicity of anions and the H-bond acidity of cations, respectively. Wherein, the H-bond between aspirin and [OAc]⁻ anion with high H-bond basicity possessed covalent feature, so ILs containing [OAc]⁻ anion has the best effective in solubilizing aspirin. However, H-bond interactions between etomidate and cations exhibited an electrostatic dominant, and moderate cation–anion interaction could weaken it. Accordingly, for etomidate, the best ILs solvent comprised a weakly interacting anion and a cation with strong H-bond acidity, that is, [BuGun][NTf₂]. This solvation difference was because aspirin with carboxyl group displayed strongly H-bond donating characteristic, whereas etomidate with no active hydrogen protons mainly formed H-bond with cations. Additionally, we found that π–π stacking interactions were of secondary importance for the solubilization of etomidate, but little for aspirin. These simulations will be helpful for experimental design new ILs to solubilize some drugs with aspirin-like or etomidate-like structures.     

Protonierung und Solvation schwacher organischer Basen. VII. 1H-NMR-spektroskopische Bestimmung der Basizität von cyclischen Ketonen

Protonation and Solvation of Weak Organic Bases. VII. ¹H-N.M.R. Spectroscopic Determination of the Basicity of Cyclic Ketones From protonation ratios for cycloalkanones of ring size C₄-C₇ in the acid system H₂O H₂SO₄ HSO₃F, determined by ¹H-n.m.r. spectroscopy, basicity and solvation parameters are estimated by application of extrapolation procedures based on the Hammett acidity function H₀ or the excess acidity X. The frequency shifts of the n̈_OH stretching vibrations of phenol in hydrogen bonded complexes with cycloalkanones have been measured. The Δν_OH values are related to the basicity parameter (H₀)_1/2.     

CORRELATION OF THE EXTRACTION OF STRONTIUM NITRATE BY A CROWN ETHER WITH THE WATER CONTENT OF THE ORGANIC PHASE*

A simple correlation has been observed between the extraction of strontium nitrate from nitric acid solution by cis-dicyclohexano-18-Crown-6 dissolved in a variety of oxygenated, aliphatic diluents and the molarity of water present in the organic phase. This correlation is attributed to the extraction of the hydrated nitrate ion and its solvation by the diluent, facilitated by the high concentration of dissolved water. Of the solvents studied, ketones yield the largest values of the extraction constant for a given water content, although C₅ and C₆ alcohols give the highest overall values.     

Protonierung und Solvatation schwacher organischer Basen. III. UV- und 1H-NMR-spektroskopische Untersuchungen zur Basizität von 1,3-Diketonen

Protonation and Solvation of Weak Organic Bases. III. U.V. and ¹H-N.M.R. Spectroscopic Investigations of the Basicity of 1,3-Diketones By ¹H-n.m.r. spectroscopy it is possible to determine separately the basicity parameters (H₀)_1/2 or pK and the solvation paramters m, ϕ or m^* for the keto and the enol form of acetylacetone. By u.v. spectroscopy only brutto parameters of the equilibrium mixture for acetyl- and benzoylacetone as for dibenzoylmethane are available.     

Theoretical studies on solvation contribution to the thermodynamic stability of mutants of lysozyme T4

Atomic solvation parameters (ASPs) are widely used to estimatethe solvation contribution to the thermodynamic stability ofproteins as well as the free energy of association for protein–ligandcomplexes. In view of discrepancies in the results of free energiesof solvation of folding for various proteins obtained usingdifferent atomic solvation parameter sets, systematic studieshave been carried out for the calculation of accessible surfacearea and the changes in free energy of solvation of folding(     

光学碱度及其在冶金中的应用

光学碱度的概念现已广泛用来解释和预测炉渣的化学性质．光学碱度利用探针离子的信息表示炉渣中的相对“自由”氧离子,是一种表达炉渣碱度的有效方法,炉渣的光学碱度即可通过测量而得到,也可由炉渣的化学成分计算出来．很多结果表明,在炼钢的渣剂控制模型中,利用光学碱度比一般碱度更能可靠地控制冶炼终点的化学成分;在钢包和中间包利用光学碱度的概念也有助于控制钢中的残余元素;也可以用来建立一些元素渣—金属平衡时的计算公式．本文系统介绍了光学碱度的概念,讨论和评价了其在冶金中的应用．     

Solvation models in the reaction between phenacyl bromide and 2-mercaptobenzimidazole

The reaction between phenacyl bromide and 2-mercaptobenzimidazole has been studied in 12 different protic and aprotic solvents. The kinetic study shows that the reaction is second-order with first-order dependence each on (phenacyl bromide) and (2-mercaptobenzimidazole). Analysis of rate data shows that there is no direct correlation between the rate constant and dielectric constant of the solvent. Correlation of rate data with different solvent parameters like hydrogen bond acceptor basicity, polarizability and solvent electrophilicity, using linear multiple regression analysis shows that the reaction is influenced by these properties of the solvent. From the regression coefficients, information on the mode of solvation of the reactants and the transition state is obtained. The reaction has also been studied at different temperatures and the thermodynamic parameters Δ H ^#, Δ S ^# and Δ G ^# are evaluated.     

Solvation and chemical engineering thermodynamics

With the continued advances in computational chemistry, solvation calculation from first principle methods is becoming a promising route for phase equilibrium modeling. However, except in a few instances, such an approach has not been widely adopted, which may be a consequence of the abstractness of solvation itself and also of the lack of a simple bridge between solvation and other thermodynamic properties. Here, we establish and summarize the relationship between solvation and other properties frequently used in phase equilibrium modeling. An important quantity, called the total solvation free energy, is introduced so that one can easily derive engineering thermodynamic models (such as an equation of state) from solvation models, or vice versa. The equations presented here are of general validity and would be useful for obtaining existing model parameters from solvation calculations and for developing new models stemming from the ideas of molecular solvation.     

On the miscibility of liquid polybutadienes

The miscibility of a new type of liquid polybutadiene and dihydroxypolybutadiene with various organic compounds was examined. The aim was to collect data which could be used in the evaluation of the role of miscibility in polyurethanes prepared from this new polymer. Qualitative tests using the cloud‐point method were made in the temperature range from laboratory conditions up to 140°C. Results were put on a common basis by the solvation equation and some characteristics derived from the electrostatic potential. Marked differences in the miscibility behavior between pure and hydroxyl‐terminated polybutadiene with hydroxyl compounds were revealed. The presence of only two hydroxyl groups in a relatively long hydrocarbon chain may thus affect properties of the molecule. Polar molecules are not, in general, miscible with polybutadienes. Polarity may be balanced and miscibility enhanced by supporting π‐electron‐interaction capabilities, H‐bond basicity, or a sufficiently long low‐polar part of a partner molecule. Other ways of improving miscibility is the nonsymmetrical placement of polar groups in the molecule structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1628–1635, 2000     

聚铁溶液的盐基度确定及其影响因素

对聚铁溶液的盐基度及其影响因素进行了探讨，指出了直接滴定所得的盐基度数值并不能真正表示羟基在聚铁分子中所占比例，盐基度的大小与溶液中铁的浓度、溶液的pH、反应温度、氧化剂的种类等因素有关，并对各因素对盐基度的影响进行了讨论。     

Interactions of chemical species with acid sites in zeolites

A detailed understanding of reaction pathways in zeolite solid acids requires knowledge about the structure and thermochemistry of all chemical species which could potentially exist along the reaction coordinate. Because some high-silica zeolites, such as H-ZSM-5, consist of a collection of nearly identical, Brønsted-acid sites, equal in concentration to the Al content, the 1 : 1 stoichiometric adsorption complexes formed by various molecules when they interact with the acid sites are well defined and relatively easy to characterize using temperature-programmed desorption, microcalorimetry, and NMR. This paper briefly reviews what is known about the reactivity, thermochemistry, and structure of complexes formed by amines, pyridines, imines, alcohols, thiols, olefins, aldehydes, ketones, and nitriles. It is shown that the thermochemistry and structure of the complexes are affected by both local effects (proton transfer or hydrogen-bonding interactions) and nonlocal effects (van der Waals interactions with the zeolite cavity). However, solvation effects in zeolites are very different from that found in acidic solutions so that the use of gas-phase reference conditions provides a much better starting point for understanding adsorption complexes, and therefore acid-catalyzed reactions, in the zeolite.     

Stability of the ash basicity in coal concentrates

Ash basicity of coal concentrates and factory furnace charges is defined for the long period of time. Four groups of the coal concentrates that are discriminated by value and stability of ash basicity are identified. The basicity of furnace charges is shown to be sometimes nonadditive relative to basicities of components. This should be taken into consideration when basicity of components is used for corrections of composition of furnace charges.     

赤泥制备混凝剂盐基度及混凝效果研究

根据盐基度测定以及混凝实验结果,对以赤泥为原料制备水处理混凝剂进行了研究.以碳酸镁为盐基度调整剂,通过正交实验确定混凝剂的最佳聚合条件如下:80℃下,pH=4,聚合时间为24 h,盐基度调整剂的投加量为60 g·L-1.对4种盐基度调整剂(碳酸镁、碳酸钙、氢氧化钙、碳酸钠)制备的混凝剂进行对比,结果发现,以碳酸钠为调整...     

低炭MgO-C质耐火材料的抗熔渣侵蚀行为

以碱度为 3.0和 1.0的钢渣对石墨含量(w)为 0、2 %、4 %、6 %和 12 %的MgO -C质试样进行了回转抗渣试验 ,并对侵蚀后试样进行了SEM、EDAX和EPMA分析。结果表明 :当石墨含量 (w)≤6 %时 ,试样在两种渣中的侵蚀深度都随石墨含量的增加而减小 ,而当石墨含量达到 12 %时 ,其侵蚀深度又都增加 ;碱度 1.0的渣对石墨含量 (w)≤ 6 %的MgO -C材料的侵蚀严重 ,而碱度 3.0的渣对石墨含量 (w)为 12 %的MgO -C材料的侵蚀严重 ;低碱度渣中Si、Fe对MgO致密层的熔损比高碱度渣中的严重。     

The strong basicity of the microporous titanosilicate ETS-10

Base-catalysed reactions in general are of great importance. In zeolite chemistry, alkali-metal-exchanged zeolites, such as zeolite X, display very strong basicity coupled with high catalytic activity. However, in order to achieve this strong basicity, considerable post-synthesis modification is necessary. In this report, it is shown that strong basicity is exhibited by the microporous titanosilicate ETS-10 in the as-prepared form which is superior to the presently known suite of zeolite catalysts. This opens up a new class of material for heterogeneous base catalysis. This revised version was published online in August 2006 with corrections to the Cover Date.     

Characterization of zeolite basicity using probe molecules by means of infrared and solid state NMR spectroscopies

This work reviews the use of pyrrole, chloroform, methanol, as well as methoxy and nitrosonium groups generated ‘in situ’, as infrared and NMR probe molecules to characterize zeolites basicity. The main results reported in the bibliography about the correlation of the spectroscopic properties of the adsorbed molecule with the framework basicity, the host–guest interactions, and the limitations in the use of these molecules as probes for zeolite basicity are discussed. Special attention is paid to the results reported for the adsorption of pyrrole and halocarbons, most specially CHCl₃ and CHClF₂ over alkali-exchanged FAU-type zeolites using IR and NMR spectroscopies.