Selective chemical reactions in supercritical carbon dioxide,water, and ionic liquids

Abstract

Alternative solvents such as supercritical carbon dioxide, water, and ionic liquids are receiving an increase of interest as better replacements for conventional solvents in chemical reactions. They have been called sustainable green solvents because they are highly promising reaction mediums for organic synthesis. This review presents an overview of some selected chemical reactions that have been developed in these green solvents with a particular emphasis on metal-catalyzed reactions.     

Silicon,Boron and Arsenic Derivatives of Phosphorus(Iv) Thioacids in Synthesis of Novel Organothiophosphorus Compounds

Abstract

We have found that S-boron 0-alkyl(ary1)dithiophosphonates react with organic substances containing reactive multiple bonds such as methyl acrylate, vinyl butyl ether, vinyl acetate under mild conditions to form products of insertions into the S-B bond. The similar results were obtained in the case of S-arsenic 0-alkyl(ary1)dithiophosphonates.     

Analytical Application of the Binary and Ternary Complexes of 2,10-Disubstituted Phenothiazines

Abstract

Phenothiazines (PT) are an important family of compound from a medical point of view. They are widely used among the tricyclic antidepressants. Their application in therapy requires methods for their determination in pharmaceuticals and body fluids. The extractive-spectrophotometric methods are very useful for these determinations. They are based on the formation of the binary and ternary complexes. Phenothiazines react with some organic substances (e.g., picric acid, alizarin S, bromocresol green, and triphenylmethane dyes) as well as with thiocyanate or halide complexes of metals [e.g., Co(II), Pd(II), Fe(III), Cr(III), Au(III), Ti(IV), Pt(IV), Mo(V), W(V), U(VI)] forming well-defined ion-association compounds. The compounds are sparingly soluble in water but quantitatively extracted from the aqueous phase into organic solvents. The extracts are intensely colored and stable for a few days. These properties are the basis for utilizing the binary and ternary complexes of phenothiazines in chemical and pharmaceutical analysis. This review described the analytical application of these complexes.     

Nodal Nomenclature–General Principles

A new, comprehensive graph-based nomenclature system for chemical substances is proposed. Substances are named by using nodal nomenclature to name graphs derived from their structures by ignoring chemical details such as atom identities, bonding, charges, etc. After the fundamental graph is named, these chemical details are introduced by modifications and additions to the name of the graph to yield the name of the actual substance. Although development of nodal nomenclature originated with problems in naming some organic systems, it is not limited to organic substances. In this paper, only general principles for naming the graph are described; applications to specific substances will be discussed in future papers.     

Flow Injection Analysis Using Potassium Permanganate: An Approach for Measuring Chemical Oxygen Demand in Organic Wastes and Waters

Abstract

A rapid and continuous analytical method based on flow injection analysis was developed for the determination of chemical oxygen demand due to organic substances in water pollution. Potassium permanganate and sulfuric acid solutions were individually pumped up as an oxidizing agent and glucose was used as a standard substance. The results for filtered organic waste and water samples were as reasonable as compared to those measured by the manual acidic permanganate method.     

4-tert-Butylcalix[8]areme as a Stationary Phase in Gas-Solid Chromatography

Abstract

The behavior of 4-tert-butylcalix[8]arene as a stationary phase in gas-solid chromatography has been tested using organic substances of different chemical and physical properties. On a column packed with the macrocycle supported on Chromosorb W Silanized, the separations of alcohols, chlorinated hydrocarbons and aromatic compounds were achieved, although the mechanism of the interactions has not yet elucidated.     

Recent developments of task-specific ionic liquids in organic synthesis

Abstract

Task-specific ionic liquids (TSILs) have received increased attention over the past few years as it is possible to form any specific ionic liquid (IL) composition depending upon user's need of the desired physical, chemical, and biological properties. These fascinating materials have shown promising results in various areas such as organic synthesis, catalysis, and specially recent emerging trend of use as functionalized ILs for chiral and nanoparticle synthesis. Present review gives an update of recent developments in the field of TSILs with emphasis on their applications in organic synthesis.     

Binding of Organic Pollutants to Soil Organic Matter

Abstract

Binding of organic pollutants to water-soluble, low-molecular weight humic substances increases their mobility in soil and their leaching, whereas binding to high-molecular weight humic substances results in unextractable residues. Water-soluble pollutants in leachate may be bound to low-molecular weight humic material, or may be free water-soluble conversion products that are slowly released from a soil-bound form, as shown for a conversion product of the insecticide aldrin. Unextractable soil-bound 4-chloroaniline was isolated by supercritical methanol extraction 16 years after application of the phenylurea herbicide buturon to soil. Biodegradation and bioavailability of unextractable soil-bound residues are greatly reduced as compared to the free compounds. For some chlorinated anilines and phenols, biomineralization and plant uptake was shown to be highest for residues bound in fulvic acids and lowest for those in humic acids. Model experiments demonstrate that chlorinated anilines form covalent bonds with humic acid precursors.     

Verwendung von Aluminiumchlorid zur Gruppenanalyse organischer Verbindungen

Summary The colour reactions of organic substances with AlCl₃ in various solvents are compared as well in heterogeneous as in homogeneous phase and the influences of substituents on the colour are investigated.Especially for the colour reactions of aluminium chloride in chloroform, produced by organic substances, there are presented some examples how to make use of this method as an aid for group analysis, for identification, and for comparison of identity.

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III. Mitt.: Talsky, G.: diese Z. 195, 171 (1963)     

Ultracentrifuge as a Versatile Tool to Study Preferential Interaction of Polymers in Mixed Solvents

Abstract

Over the past five decades the analytical ultracentrifuge has been a versatile tool in the study of macromolecules and colloidal particles. Several textbooks [1–4] and review articles [5–10] deal with experimental techniques and theories for complete characterization of macromolecular species. However, the first published articles on the analytical ultracentrifuge dealt with the analysis of particle size distributions in suspensions of inorganic colloids. The emphasis has now shifted to organic polymers following the discovery that a large number of such polymers exist in nature. Before the development of the ultracentrifuge, the existence of such giant molecules was not recognized; the molecular kinetic units of proteins and of high organic polymers in solution were simply thought of as clusters of much smaller molecules, forming particles of undefined mass. Beginning with the elegant investigations of Svedberg [11, 12] on ultracentrifugation, such substances were revealed to be macromolecules, large because they contain a huge number of atoms connected together by primary chemical bonds [13]. Following a long and fruitful series of investigations in the early twenties and thirties, Svedberg wrote in one of his articles [12], “the proteins are built up of particles possessing the hallmark of individuality and therefore are in reality giant molecules. We have reason to believe that the particles in the protein solutions and the protein crystals are built up according to a plan which makes every atom in them indispensable for the completion of the structure.” Almost at the same time, it was Staudinger [14] who clearly demonstrated that substances such as polystyrene and natural rubber exist in solution without change in molecular weight regardless of the solvent employed .     

Trends in Coatings Technology

Abstract

Human intelligence has created a variety of chemical substances which have greatly contributed to the well-being of the human race. Today's coatings consist of many of these chemical substances in combination. There are probably no less than several thousand kinds of raw materials for coatings with natural and synthetic materials combined. While the accelerated technological progress in the past greatly improved the human living standard, it has now come to adversely affect the environment. Many problems have been recognized, such as air and water pollution by chemical substances, serious effects on forest and lakes by acid rain, destruction of the ozone layer by chlorofluorocarbons, global warming caused by carbon dioxide in the atmosphere, etc. In order to cope with these problems, world leaders came together at the UN Conference on Environment and Development in Rio de Janeiro. The year 1995 has become a historically significant year for human beings world-wide.     

Future Trends in Rubber Processing: The Chemistry of Rubber Processing

Abstract

Future trends in rubber processing are discussed with special emphasis on the chemical aspects that might be used to develop new and improved properties of rubber materials. They include optimization of such properties as resiliency and “softness,” of reinforcement and the control of crosslinking, and of the crosslink densities of rubbers during vulcanization.     

Characterization of Sediments in Aerated Lagoons and Waste Stabilization Ponds

Abstract

Sediments affect the performance of aerated lagoons and waste stabilization ponds in many ways. This paper presents the results of a three years study conducted on real-size facilities and implementing numerous analytical procedures. Sediment accumulation rates and physico-chemical characteristics are described as well as their activity in terms of oxygen consumption and exchange rates with overlying waters.

The deposits had a mean accumulation rate of 4.7 cm per year, their main characteristics being low viscosity and high organic content (>30%). They also accumulated numerous organic and mineral compounds, such as nutrients and heavy metals. Vertical concentration profiles, measured in the sediment and interstitial liquid phases, are presented and discussed. These results emphasize the importance of surface activity.

Sediment oxygen demand, which can be divided into biological and chemical components, ranged from 1 to 3 gO₂/m²·d. Finally, the exchange rates of COD, nitrates, ammonia and orthophosphates existing at sediment-water interface were quantified under several redox conditions and substrate additions.     

Controlling the Fenton Reaction for Soil Remediation

ABSTRACT

This paper describes the use elemental iron to control the Fenton reaction, a process in which ferrous ion reacts with hydrogen peroxide. It is widely believed that the Fenton reaction produces free radicals that can degrade organic chemicals. By using elemental iron in place of ferrous iron, we found that the vigor of the Fenton reaction can be controlled, and therefore can be used more effectively to remediate contaminated soil.

Laboratory studies were done to compare the elemental iron approach with the original ferrous salt approach. It was found that elemental iron can increase the effectiveness of the Fenton reaction in degrading organic chemical such as Pentachlorophenol (PCP). The mechanism of control lies in the production of ferrous irons from elemental iron in the presence of hydrogen peroxide.     

Some Applications of Computerized GC-MS to the Determination of Biogenic and Anthropogenic Organic Matter in the Environmentt

Abstract

This is an overview of the application of organic mass spectrometry and ancillary techniques to the analysis of organic matter in environmental research. Such organic matter is usually analyzed in terms of gas, bitumen (lipids), and “kerogen”, with asphaltenes and humic substances for some samples. This approach is illustrated with some examples and the origin, the environmental history and the nature of secondary products of this organic matter can be evaluated by using the data derived from both specific molecular and bulk chemical (also physical) analyses. Evaluations of production and fluxes and cross-correlations can thus be made by the application of the same separation and analytical procedures to samples from different environmental compartments (eg., biota, atmosphere, hydrosphere, lithosphere, etc.).     

Indirect Determination of Pyrrolizidine Alkaloids by Flame Atomic Absorption Spectrometry

Abstract

This paper studies the formation and extraction of ion pairs of some alkaloids derived from pyrrolizidine. The substances studied are Nemorensine, Platyphylline, Senecionine and Seneciphylline, and the ion pairs studied and extracted are formed with Bil₄. The method consists of extracting an ion pair between the organic base and the inorganic complex, the metal is measured in the organic phase (1,2 dichloroethane) by Flame AAS. The optimal experimental conditions, pH, concentration of BiI₄ ^?, shaking time, phase ratio, number of extractions, and the range of calibration are studied for these substances. The linear range in organic phase is 0.13–1.91 mg.mL^?1. The standard deviation of the method varies between 2.4–3.2%, depending on the substance analyzed. The interferences produced by various substances are studied.     

Artifact Formation In The Soxhlet Extraction Of Environmental Samples With Acetone

Abstract

A study was performed to confirm suspected artifactual formation of acetone derivatives during the Soxhlet extraction of soil samples with acetone. The conditions employed simulated very closely those normally employed for the extraction of soils for neutral and moderately polar organic compounds such as pesticides. A series of acidic, neutral, and basic organic-free soils were extracted with hexane/acetone solvent mixture and the extracts concentrated in a Kuderna-Danish apparatus. The extracts were analyzed by capillary column gas chromatographic mass spectrometry. In nearly all cases, simple dimeric products such as diacetonecohol and mesityl oxide were formed in varying amounts. The acidified and basic soils yielded complex mixtures of dimers, trimers, tetramers and other complex homologs. Some of the more common substances found include phorone, mesitylene and isophorone. The latter substance is listed as an EPA priority pollutant.     

False Detection of Cyanide Ion in Photographic Processing Waste Solutions Using Standardized Reference Methods

Abstract

Although cyanide compounds are not incorporated in photographic processing solutions, false detection of cyanide ion is often encountered during the determination of total cyanide by various standardized methods such as ISO, ANSI and JIS. Various organic compounds and nitrogen compounds in the processing solutions were examined because of this false detection. The results suggest that hydrogen cyanide is formed by a reaction between these compounds during the distillation process for the separation of total cyanide, even though ISO, ANSI and JIS were used. The results support the following three mechanisms of cyanide formation involved in the process: (1) Hydroxylammonium salts reacts with another ingredient, formaldehyde, to form formaldoxime, which then decomposes to HCN. (2) Hydroxylammonium is oxidized by air to form nitrite ion, which subsequently reacts with organic compounds such as aminocarboxylic acids and aromatic amines (the colour-developing agent) to form HCN. (3) Potassium permanganate oxidizes aromatic amines to form HCN.     

Dichromate method for the determination of chemical oxygen demand

The oxidizability of organic substances of different classes was studied under the conditions of an official procedure for the determination of chemical oxygen demand (COD) with and without using Ag₂SO₄ as a catalyst. Organic substances can be divided into three groups: easily oxidizable compounds that are oxidized by 80–100% without a catalyst; medium-oxidizable compounds that are oxidized by 40–80% in the absence of a catalyst; and hardly oxidizable compounds that are oxidized by less than 40% without a catalyst. It was shown that, in the presence of a catalyst, not all organic substances are completely oxidized; therefore, the verification of the results of the determination of COD using easily oxidizable potassium hydrophthalate and glucose cannot be reliable in the presence of more hardly oxidizable substances. A standard mixture containing ethylene glycol, acetic acid, dimethylformamide, and nitrobenzene was proposed to verify the results of determining COD in waters of any type. The error in COD values found in a standard mixture varied in the range from 15 to 840 mg O/L. A modified procedure for the determination of COD in pure waters was proposed.