Prediction of aqueous solubility of organic compounds by the general solubility equation (GSE)

The revised general solubility equation (GSE) is used along with four different methods including Huuskonen's artificial neural network (ANN) and three multiple linear regression (MLR) methods to estimate the aqueous solubility of a test set of the 21 pharmaceutically and environmentally interesting compounds. For the selected test sets, it is clear that the GSE and ANN predictions are more accurate than MLR methods. The GSE has the advantages of being simple and thermodynamically sound. The only two inputs used in the GSE are the Celsius melting point (MP) and the octanol water partition coefficient (K(ow)). No fitted parameters and no training data are used in the GSE, whereas other methods utilize a large number of parameters and require a training set. The GSE is also applied to a test set of 413 organic nonelectrolytes that were studied by Huuskonen. Although the GSE uses only two parameters and no training set, its average absolute errors is only 0.1 log units larger than that of the ANN, which requires many parameters and a large training set. The average absolute error AAE is 0.54 log units using the GSE and 0.43 log units using Huuskonen's ANN modeling. This study provides evidence for the GSE being a convenient and reliable method to predict aqueous solubilities of organic compounds.     

Radiation-induced nitration of organic compounds in aqueous solutions

Radiation-induced nitration of organic compounds in aqueous solutions was studied. It was found that γ-irradiation of solutions containing acetic and nitric acid and/or their salts gives nitromethane. Dependences of the product yield on the absorbed dose and the contents of components were established. The mechanism of radiation nitration involving radicals is discussed.     

Hetarylation of organic compounds (review)

Reactions of the direct introduction of nitrogenous aromatic heterocycles into nucleophilic organic compounds with the use in situ of N-acyl salts of heterocyclic cations and also of heteroaromatic anion radicals are discussed.     

Trace analysis of organic compounds

The trace analysis of organic compounds presents a number of additional difficulties in comparison with the trace analysis of inorganic compounds. Thus special problems arise in sampling and in the storage of samples (e. g. because of the instability of many organic compounds). It is also difficult to choose suitable mild separation methods and to find highly sensitive, molecule-specific determination methods.     

Development of soft plasma ionization (SPI) source for analysis of organic compounds

We present a newly designed soft plasma ionization (SPI) source developed for mass spectrometric study of organic compounds in this study. The SPI cell having a relatively small size consists of a hollow anode and a hollow mesh cathode. The voltage–current characteristic depending on the pressure was investigated, indicating that it has similar characteristics to conventional hollow cathode glow discharges. To investigate the emission characteristics of the SPI source, some molecular band emission spectra (N₂, N₂⁺ and OH⁺) were measured by using argon and helium discharge gases. The SPI source was installed to a commercially used quadrupole mass analyzer for analyzing organic compounds. To demonstrate the SPI source, the mass spectra of some organic compounds (methylene chloride, toluene, benzene, cyclohexane and chloroform) were measured. The organic compounds were ionized with good stability in the plasma, and the fragmentation depended on the applied current. When helium and argon gases were used as the discharge gas, the helium plasma was more suitable for SPI-MS rather than argon because the argon plasma not only suffers from spectral interference but also has lower sensitivity.     

Simplified analysis of organic compounds in headspace and aqueous samples by high-capacity sample enrichment probe

A sample enrichment probe (SEP) consisting of a thin rod of an inert material and provided at one end with a short sleeve of polydimethylsilicone rubber was used for the high-capacity sample enrichment of analytes from gaseous and aqueous samples for analysis by gas chromatography (GC) and its hyphenated techniques. The silicone rubber was exposed to the analytical sample, after which the end of the rod carrying the silicone rubber was introduced into the injector and the analytes thermally desorbed and analysed by GC. This technique is similar to, but differs from, solid-phase microextraction (SPME) in that a much larger volume of the sorptive phase is employed, the sorptive phase is not introduced into the inlet of the GC via a needle and the injector is opened to the atmosphere for the introduction and removal of the SEP. In the determination of volatile and semi-volatile organic compounds in gaseous and aqueous media, the SEP technique gave results comparable with those obtained by the stir-bar-sorptive extraction (SBSE) and high-capacity sorption probe (HCSP) techniques. Implementation of the SEP technique requires only minor adaptations to the gas chromatograph and does not require any auxiliary thermal desorption and cryotrapping equipment.     

Heterocyclic compounds as organic luminophores (review)

A review of heterocyclic compounds having luminescence properties is given. Methods for the preparation of some of them, the relationship between structure and luminescence, and their areas of application are examined.     

Kinetics of oxidation of organic compounds by silver(II) in aqueous perchloric acid solution. Part 5

Summary The kinetics and mechanism of oxidation of a series of alcohols, namely cyclohexanol, cyclopentanol, pentan-2-ol and benzyl alcohol, by silver(II) perchlorate in perchloric acid solution. have been investigated by the stopped-flow technique. These oxidations proceed through two parallel pathways involving Ag²⁺ and AgOH⁺ species. In the case of benzyl alcohol, the hydroxo species, which has been found to be almost universally reactive toward different organic substrates, is inactive; this behaviour has been interpreted in terms of interaction of the oxidant with the aromatic moiety in the alcohol. The reactivities are discussed in terms of substrate reaction sites with reference to electronic availability and reaction products.     

Oxidative degradation of nitrogen-containing organic compounds: vaccum-ultraviolet (VUV) photolysis of aqueous solutions of 3-amino 5-methylisoxazole

The oxidative degradation of 3-amino 5-methyl isoxazole initiated by the VUV photolysis of water at 172 nm has been studied. Mineralization of CO₂, H₂O, NO ₃ ^– and NH ₄ ⁺ is more efficient when reductive conditions (argon saturated solutions) are favoured. Formation of compounds which cannot be completely oxidised to CO₂ is observed. Experiments performed under strictly oxidative conditions show higher yields of these inert compounds and, hence, incomplete mineralization. Cyanide was formed in concentrations lower than 5×10^–5 mol/l. In alkaline aqueous solutions, cyanide is completely transformed into CO ₃ ^2– , NH ₄ ⁺ and NO ₃ ^– during the irradiation time needed to mineralize the isoxazole. Therefore, cyanide does not present a potential risk for the use of the VUV photolysis for isoxazole degradation. Similarly, organic nitrogen is converted into both, NO ₃ ^– and NH ₄ ⁺ . The relative concentrations of the two ions depend on total irradiation time, oxygen saturation and reactor geometry. A sequence of reactions is proposed and discussed.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday     

Metal(loid)organic compounds in contaminated soil

13 samples of soils contaminated with petrol, coaly residues, shredder and domestic waste have been investigated by low temperature gas chromatography with plasma mass spectrometry detection after sample derivatisation by hydride generation (HG/LT-GC/ICP-MS). 24 organic compounds of 9 elements could be analysed, one fifth of them exceeding the concentration of 1 microg/kg. These results are roughly comparable with those on harbour and river sediments, and are discussed in respect to a preliminary evaluation of the emission potential of solid waste and contaminated soil as well as waste treatment processes.     

Degradation of electrochemical active compounds in aqueous organic redox flow batteries

Aqueous organic redox flow batteries (AORFBs) represent a promising energy storage technology that may enable the grid-scale integration of intermittent renewable energy. The water-soluble, redox-active organic species that are utilized to reversibly store electricity are the most critical performance-determining components in AORFBs. To ensure affordability and competitiveness in practical installations, it is of vital importance to enhance the structural stability and long-term durability of organic electrolytes, ultimately decreasing their levelized cost. Herein, we summarize the proposed decomposition mechanisms for representative organic electrolytes, including quinones, viologens, nitroxide radicals, and ferrocene derivatives. By reviewing the influence of molecular engineering on the side reactions of electrolytes, we intend to provide a better understanding of the decisive factors and inspire further attempts to design structurally robust and cycling-stable electrolytes for AORFB. Finally, we provide possible directions and prospects for future AORFB research.     

Isolation and determination of volatile organic sulphur compounds in aqueous solutions

Summary A procedure has been worked out for isolation and determination of volatile organic sulphur compounds in water. These compounds are isolated from an aqueous sample by countercurrent thin-layer head-space (TLHS) technique. After isolation, the sulphur compounds are burned in a quartz tube and the combustion products (SO₂/SO₃ mixture) are absorbed by a 10% solution of hydrogen peroxide. The resulting sulphuric acid is introduced into the heated part of a quartz tube, where the presence of tungsten trioxide at 1150°C ensures its complete decomposition. The sulphur dioxide formed is titrated microcoulometrically with iodine. Organic halogen compounds usually present in different waters do not interfere. The complete procedure has been tested on model solutions of sulphur compounds in the concentration range of 10–200 g S/l.     

The use of copper(III) complex compounds for the thermochemical analysis (DIE) of different organic substances

Potassium diperiodatocuprate(III), K₇[Cu(IO₆)₂], was tested as a reagent for the determination of mono- and disaccharides by means of direct injection enthalpimetry. The reagent reacted readily with acyclic polyhydroxy compounds, the reaction proceeding the better, the more hydroxy groups there were in the substance and the closer the hydroxy groups were one to the other. It also reacted readily with phenols, the polyhydric ones in particular. Carbonyl and amino compounds mostly didn't react or did so slowly, but reacted readily in the presence of some other reactive group such as hydroxy, sulphhydryl or thioxo group. Semicarbazide reacted readily, presumably due to the presence of the reactive-CO-NH-group. It is concluded that carboxy groups in the proximity of hydroxy groups exercise a positive effect on the reaction. The presence of a nitro or sulphonic acid group has a negative effect on the course of the reaction with the copper(III) compound.

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Zusammenfassung Kalium-diperiodatocuprat(III), K₇[Cu(JO₆)₂], wird als Reagenz für die Bestimmung von Mono- und Disacchariden durch direkte Injektionsenthalpimetrie vorgeschlagen. Es wurde festgestellt, daß das Reagenz leicht mit azyklischen Polyhydroxy-Verbindungen reagiert, und zwar umso besser, je mehr Hydroxylgruppen die Substanz enthält und je näher diese beieinander liegen. Das Reagenz reagiert leicht mit Phenolen, insbesondere wenn diese mehrere Hydroxylgruppen enthalten. Carbonyl- und Aminoverbindungen reagieren meistens nicht oder nur langsam, aber leicht in Gegenwart einiger anderer reaktiver Gruppen, wie Hydroxy-, Sulfhydryl- oder Thioxogruppen. Semicarbazid reagiert leicht, wahrscheinlich wegen der reaktiven Gruppe-CO-NH₂-. Es wird der Schluß gezogen, daß Carboxylgruppen in der Nachbarschaft von Hydroxylgruppen eine positive Wirkung auf die Reaktion ausüben. Die Anwesenheit der Nitro- oder Sulfonsäuregruppe wirkt sich negativ auf den Verlauf der Reaktion mit Kupfer(III)-Verbindungen aus.

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- K₇[u(IO₆)₂] — - . , . , . , , . . , -, - , . , , , -NH-. , , , , - .

     

Applications of bismuth(III) compounds in organic synthesis

This review article summarizes the applications of bismuth(III) compounds in organic synthesis since 2002. Although there are an increasing number of reports on applications of bismuth(III) salts in polymerization reactions, and their importance is acknowledged, they are not included in this review. This review is largely organized by the reaction type although some reactions can clearly be placed in multiple sections. While every effort has been made to include all relevant reports in this field, any omission is inadvertent and we apologize in advance for the same (358 references).