On the Decarboxylation of Metal Trichloroacetates

The decarboxylation of trichloroacetate ion in basic solvents produces the intermediate trichlorocarbanion which may split into chloride and dichlorocarbene or combine with a proton to chloroform. Conditions under which protonation predominates were examined for possible use of the reaction for synthesizing metal compounds in non-aqueous solvents.     

Effect of the mobile phase composition on the retention behaviour of diphenylsilica pre-coated plates

The retention of some rifamycins and steroids on diphenyl bonded pre-coated silica gel plates, in relation to the mobile phase used, was examined by thin-layer chromatography. Neat organic solvents, non-aqueous and aqueous binary mixtures were tested as eluents. By comparison of retention data for rifamycins and steroids, respectively, under non-aqueous and aqueous conditions, a dual retention mechanism on this diphenyl phase was found. Interactions with the residual silanol groups seemed to prevail when employing as mobile phase the more lipophilic solvents tested, such as chloroform or dichloromethane, whereas interactions with the aryl groups of the bonded phase prevailed when using high polarity alcohols or aqueous mixtures. As a consequence, by changing the mobile phase, a large variation in selectivity with a concomitant change in retention order of the test compounds was observed.     

Non-aqueous capillary electrophoresis using non-dissociating solvents. Application to the separation of highly hydrophobic oligomers

The application of non-aqueous capillary electrophoresis for the separation of very hydrophobic oligomers has been studied. N-Phenylaniline oligomers having degrees of polymerisation (n) of 2, 4, 6, and 8 were taken as model compounds. Capillary electrophoresis could be performed using a mixture of non-aqueous solvents with a high percentage of solvents with a low dielectric constant. These solvents, such as tetrahydrofuran (THF), chloroform or dichloromethane, are needed to solubilise the hydrophobic solutes in the electrolyte. The composition of the solvent mixture and the nature of the acid added to the electrolyte, which is needed to obtain electrophoretic motion of the N-phenylaniline oligomers, are discussed in detail. Next, other parameters such as ionic strength, injection time, electric field, and temperature were investigated too and their influence on the separation is discussed as well. The existence of a reversed (anodic) electroosmotic flow in a fused-silica capillary containing a THF-methanol mixture under acidic conditions is reported.     

The effect of water on separations in non-aqueous capillary electrophoresis systems

Summary Water, in concentrations up to 10%, has been added to organic solvents (dimethylsulphoxide,N-methylformamide, acetonitrile and methanol) used as the buffer solvents in electrophoresis media for non-aqueous capillary electrophoresis. Anionic and cationic test substances have been used to study the effect on separation selectivity and efficiency. The effect on the electroosmotic flow has also been studied. Water added in concentrations up to 0.5% had only a minor effect on the separation selectivity, efficiency or electroosmotic flow in the systems studied. These results indicate that small variations in the water-content of organic solvents are of only minor importance to the reproducibility of non-aqueous capillary electrophoresis systems. The reproducibility of selectivity might, however, be slightly improved by adding 0.1–0.5% water, because true non-aqueous solvents are likely to cause problems as a result of the variable absorption of water.     

A comparative study on gamma irradiation of unconjugated bilirubin in aqueous and non-aqueous solutions

Dilute aqueous and non-aqueous solutions of bilirubin were exposed to gamma radiation to examine the effects of ionizing radiation on the concentrations of a specimen of this nature. The ionising radiation emanated from a (137)Cs source, and was applied to 5.2 x 10(-2) mmol L(-1) solutions of the unconjugated specimen in 0.05 mol L(-1) aqueous NaOH and chloroform. Depletion of bilirubin after exposure was common to both solvents. Complete degradation was accomplished with doses in excess of 100 Gy. In the case of NaOH, it was found that the presence of molecular oxygen contributed more efficiently to the degradation process, than irradiation in air. When the experimental conditions were changed to nitrogen, the degradation process was suppressed. The sole by-product of merit originating from the NaOH work was the short-wavelength isomer of biliverdin, at 330 nm. In the case of chloroform, the exclusive product of interest was characterised as the long-wavelength isomer of biliverdin that absorbs in the broad region commencing from about 620 nm. The non-aqueous study was conducted in the presence and absence of molecular oxygen, with no significant changes in the results. Optimum production of the isomers in question occurred at a gamma dose of about 80 Gy. The general species of interest were monitored spectrophotometrically, and the results were treated mathematically to facilitate evaluation of the data. Our work represents the development of a facile gamma-ray method for the exclusive production of specific isomers of biliverdin, which are useful components in biosynthetic research.     

Benzyltriphenylphosphonium Chlorochromate: A Mild and Novel Reagent for Oxidation of Benzylic and Allylic Alcohols Under Non-Aqueous and Aprotic Conditions or Microwave Conditions

This paper describes the oxidation of benzylic and allylic alcohols under non-aqueous and aprotic conditions or microwave conditions using benzyltriphenylphosphonium chlorochromate (1) PhCH₂PPh₃CrO₃.HCl which has been prepared by mixing an aqueous solution of benzyltriphenylphosphonium chloride with CrO₃ in 6 N HCl at room temperature. This reagent is stable orange powder which may be stored for months without loss of its activity. This compound is readily soluble in organic solvents such as acetonitrile, chloroform and dichloromethane and slightly soluble in carbon tetrachloride, ether and hexane. the oxidation under microwave conditions is much more faster.     

Specific-ion effects in non-aqueous systems

It is widely acknowledged that specific-ion effects are ubiquitous in aqueous systems and undoubtedly are essential to the fundamental processes of life, although a deep fundamental understanding of specific-ion effects remains an important challenge. Specific-ion effects in non-aqueous solvents are known but have attracted far less attention, yet knowledge of specific-ion effects in non-aqueous systems is likely to provide important information for guiding, evaluating and testing our theories of specific-ion effects. Here, the literature on specific-ion effects in non-aqueous solvents is surveyed with a view to determining if the Hofmeister series or lyotropic series so universally observed in aqueous systems is widely evident in non-aqueous systems. Particular attention has been applied to experiments on non-aqueous systems that are known to exhibit Hofmeister series in aqueous systems with the aim of determining if a consistent ion ordering in the strength of specific-ion effects is observed in other solvents. We find that specific-ion effects are ubiquitous in non-aqueous solvents, that both Hofmeister and lyotropic series are widely observed, although not necessarily for the same class of experiment. Moreover, we find that Hofmeister and lyotropic series are observed in non-aqueous solvents even for experiments in which these series are not observed for water. Additionally, series reversal is seen for a given experiment when the solvent is changed. All this poses significant challenges for our understanding of specific-ion effects in aqueous and non-aqueous systems and also provides guideposts for future investigations.     

乙醇-环己烷体系中NaI活度系数的测定与计算

由于非水溶剂的应用日趋广泛,促使物理化学工作者对于溶剂和溶液性质进行研究,同时开展了有关物理化学数据的测定和积累工作,以利于指导实践[1]。目前文献报道含水混合溶剂中的电解质活度系数较多,但非水混合溶剂中电解质活度系数报道较少。电解质浓溶液活度系数的计算方法目前应用较广的是Pitzer半经验算法[2]。Pitzer的算法中具体物系的β(0)、β(1)等系数需从实测活度系数数据拟合求得。孙仁义等通过测定汽液平衡盐效应的方法研究了盐在混合溶剂中的活度系数[3-4]。最近孙仁义等[5]提出了双液比固定条件下含盐体系汽液平衡数据热力学一…     

Effectivity of solvents-A new approach in non-aqueous acid-base titrimetry

A new approach for selection of a suitable solvent system as a medium for non-aqueous acid—base titration is proposed. The essence of the approach is the development of a new criterion called “effectivity”. The latter is based on consequences of the Brønsted and Izmailov acid—base theories and represents a quantitative measure for improving or worsening the titration conditions of acids and bases in non-aqueous solvents as compared with water. The “effectivity” E is given by the relation E = ΔpK_s - ΔpK_s where ΔpK_s is the difference between the logarithmic values of the autoprotolysis constants of water and the solvent in question, and ΔpK is the so-called medium effect. The latter is a constant value which shows that acids and bases with the same charge alter their strength to the same extent when transferred from water into a non-aqueous solvent. The medium effect is calculated by statistical treatment of a great number of acid—base constants determined experimentally both in water and the non-aqueous solvent in question. The effectivity of the solvents most often used in non-aqueous acid—base titrimetry, determined by this approach, shows that in many cases these solvents offer significant advantages over water, but drawbacks are also observed. Some limitations of the approach are discussed. Special attention is paid to dimethylsulphoxide and its mixtures with water, which prove to be highly effective media for the acid—base titration of many substances.     

Non-aqueous capillary electrophoresis

The benefits of non-aqueous capillary electrophoresis have been described in a number of recent publications. The wide selection of organic solvents, with their very different physicochemical properties, broadens our scope to manipulate separation selectivity. The lower currents present in non-aqueous solvents allow the use of high electric field strengths and wide bore capillaries, the latter in turn allowing larger sample load. In many cases detection sensitivity can also be enhanced. The potential of non-aqueous capillary electrophoresis is discussed throughout the paper, and the feasibility of capillary electrophoresis under non-aqueous media is demonstrated with reference to several applications.     

Capillary zone electrophoresis in non-aqueous solutions: pH of the background electrolyte

Although the establishment of a pH scale and the determination of the pH in water is not problematic, it is not a straightforward task in non-aqueous solvents. As capillary zone electrophoresis (CZE) in organic solvents has gained increasing interest, it seems to be valuable to re-discuss the concept of the pH in such media, especially pointing to those aspects, which make pH measurement uncertain in non-aqueous solvents. In this review, the relevant aspects when dealing with primary standard (PS) and secondary standard (SS) as recommended by the International Union of Pure and Applied Chemistry (IUPAC), and the usage of the operational pH are discussed with special emphasis to non-aqueous solvents. Here, different liquid junction potentials, incomplete dissociation of the electrolytes (especially in solvents with low or moderate relative permittivity) and the occurrence of homo- and heteroconjugation must be taken into account. Problems arising in capillary zone electrophoresis practice are addressed, e.g. when the background electrolyte (BGE) consists of organic solvents, but the measuring electrode (normally the glass electrode) is calibrated with aqueous buffers, and the liquid junction potentials between the solvents do not cancel each other. The alternative concept of establishing a certain pH is described, using mixtures of reference acids or bases with known pKa in the organic solvent, and their respective salts, at a certain concentration ratio, relying to the Henderson-Hasselbalch equation. Special discussion is directed to those organic solvents most common in capillary zone electrophoresis, methanol (MeOH) and acetonitrile (ACN), but other solvents are included as well. The potential significance of small amounts of water present in the organic solvent on changes in pKa values, and thus on the pH of the buffering components is pointed out.     

硫碘循环制氢中Bunsen反应新方法的研究进展

热化学硫碘(S-I)循环分解水是目前有较高效率且可以在相对较低温度条件下进行的制氢方法之一。 其中的Bunsen反应作为循环的核心步骤尤为重要。 为了更方便有效地分离Bunsen反应的生成物硫酸与氢碘酸,许多学者研究了Bunsen反应的新方法。 本文对非水溶剂中的Bunsen反应和电化学Bunsen反应两种新方法进行了综述。 讨论了非水溶剂中实现反应生成物分离的方法,对比了各种非水溶剂的性质及其优缺点。 目前,所发现的溶剂在分离生成物方面已达到要求,可用于Bunsen反应,但溶剂的回收再利用比较困难。 概述了电化学Bunsen反应的研究现状,对目前在电化学Bunsen反应中有突破进展的两个团队的工作进行了对比。 现今对该方法的探讨主要集中在反应基础特性方面,未来可以加强电化学Bunsen反应机理、反应电池结构设计与优化、以及新型S-I循环系统构造的研究。     

Cyclic voltammetric study of vanadium(V)/(IV) as a redox catalyst in non-aqueous media

A basic study for possible kinetic-catalytic methods in non-aqueous solvents with vanadium as a redox catalyst is described. The redox behaviour of the V(V)/V(IV) couple is studied by cyclic voltanimetry at a carbon electrode in acetonitrile. Vanadium oscillates between the two oxidation states without chemical side reactions, and is thus promising as a redox catalyst in non-aqueous media. The oxidizing power of the couple is increased with increasing p-toluenesulphonic acid concentrations and is decreased in the presence of solvents of increasing donor strength. The influence of common activators on the formal potential of the couple is discussed.     

八乙基金属卟啉的轴向配位反应研究及稳定常数测定

测定了八乙基金属卟啉 (OEP) M中当M=Zn, Cu, FeCl 或 MnCl时在CH2Cl2, N,N-二甲基甲酰胺(DMF), 二甲亚砜(DMSO), 吡啶(Py)等4种不同非水溶剂中的紫外-可见光谱, 探讨了溶剂的性质对八乙基金属卟啉光谱的影响. 结果表明八乙基锌、铁、锰卟啉在CH2Cl2中能够与配位溶剂如DMF, DMSO或pyridine 等发生轴向配位反应生成五配位或六配位的金属卟啉配合物. 用微量光谱滴定法测定了Zn、 Fe、 Mn等金属卟啉和配位溶剂发生轴向配位反应的稳定常数(logK). 讨论了中心金属离子的电负性以及配位溶剂的给电子能力对稳定常数的影响.     

Optical absorption spectroscopic studies on holmium(III) complexes with beta-diketone and heterocyclic amines: the environment effect on 4f-4f hypersensitive transitions

The optical absorption spectra of [Ho(acac)(3)(H(2)O)(2)].H(2)O, [Ho(acac)(3)phen] and [Ho(acac)(3)bpy] (where acac is the anion of acetylacetone; phen is 1,10-phenanthroline and bpy is 2,2'-bipyridyl) complexes in the visible region, in a series of non-aqueous solvents (methanol, ethanol, isopropanol, chloroform, acetonitrile and pyridine.) have been analyzed. The largest intensity variation was observed in the (5)G(6)<--(5)I(8) (centered at 450 nm), and (5)G(5), (3)H(5), (3)H(6)<--(5)I(8) (centered at 360 nm) transition regions. The band shape and oscillator strength of the hypersensitive transitions display pronounced changes as compared to Ho(3+) aqua-ion. The band shapes of the hypersensitive transitions show remarkable changes on passing from aqueous solution to various non-aqueous solutions which is the result of change in the environment about the Ho(III) ion in the various solutions and suggests coordination of solvent molecule(s), in some cases. The results clearly show that among the solvents studied pyridine is the most effective in promoting the 4f-4f spectral intensity. It has been inferred from this study that 2,2'-bipyridyl is a stronger ligand for heavier lanthanides. A comparative account of hypersensitivity in the present complexes with those of other adducts of Ho(beta-diketoenolate)(3) with heterocyclic amines is discussed. The TGA analyses showed that the phen complex is thermally more stable over its bpy analogue.     

镥单酞菁和镥双酞菁电子转移过程的研究

本文用循环伏安法研究镥单酞菁和镥双酞菁在非水溶剂中的电化学行为,获得了相应的氧化还原反应半波电位E1/2,测定了其中四个氧化还原反应的电子转移速度常数ks。指出非水溶剂对镥单酞菁和镥双酞菁的电化学行为具有程度不同的影响。     

Identification of isothiocyanates (Mustard oils) and liquid primary amines via the formation of 1-substituted 2-tetrazoline-5-thione

The oscillometric method is suggested for the determination of alkali salts of organic acids in non-aqueous media. In the titrations of organic sodium and potassium salts the influence of water content and dielectric constant of non-aqueous solvents on the slopes of the titration curves was investigated. Errors obtained were in the range of±0.6 to 1.5%.     

The solvent extraction of trace antimony(V)

An investigation of the extraction of trace amounts of antimony(V) from aqueous hydrochloric acid solutions into various others and chloroform has been carried out. Before extractions were made, mutual solubility studies of the two-phased systems were conducted. Then extraction experiments were performed using original aqueous acid concentrations from 0 to 12N and non-aqueous phases of ethyl ether, isopropye ether, isoamyl ether, n-hexyl ether, and chloroform. Dielectric constant determinations were made in the equilibrated non-aqueous phases, and spectrophotormetric and salting-out studies were carried out on the ethyl ether system. It was found that the isopropyl ether system presents the most advantageous conditions for the extraction of trace antimony(V)     

Some solvent effects on the solvent extraction of 8-quinolinol

The distribution constants of 8-quinolinol between water and a series of substituted aliphatic hydrocarbons, at 25 degrees , are reported. The results are discussed in terms of dielectric constant and solubility parameter of the solvents. For 8-quinolinol, and possibly for its chelates, bromochloromethane, dibromomethane and chloroform seem to be about the best solvents, in that order. Among the solvents studied, chloroform shows significantly higher values than expected; the deviation may be explained as a specific interaction of the hydrogen- bonding type.