The characterization of and the evolution of molecular hydrogen by the μ-hydrido-bridged cyclodecyl cation. Relevance to the question of hydrocarbon protonation by superacids

The observable cyclodecyl cation is established as having a 1,5-μ-hydrido-bridged structure and most probably exists as a mixture of conformational isomers. This solution carbocation is unique in organic chemistry in that it evolves molecular H₂ at temperatures below -100°C to give the 9-decalyl cation. The mechanism of this reaction is postulated to involve a pentacoordinated carbocation intermediate or transition state with a structure identical to what one would get by protonating the bridgehead C-H bond of decalin. Since conversion of decalin to the decalyl cation in superacids is not accompanied by significant H₂ production, the mechanism of these two reactions must be different, and in the latter case could not involve a protonated pentacoordinate carbocation intermediate, as has been postulated.     

Reply to the comment by F. Malatesta on: “Factorizing of a concentration function for the mean activity coefficients of aqueous strong electrolytes into individual functions for ionic species” by A. Ferse and H.-O. Müller

The arguments of Malatesta (J Solution Chem 29:771–779, 2000; Fluid Phase Equil 295:244–248, 2010) exclude the experimental determination of individual ion activity coefficients. I agree that a measurement of single-ion activity coefficients is impossible. But the comment of Malatesta (J Solid State Electrochem (in press), 2011) in the connection with the purely mathematical procedure developed by Ferse and Müller (J Solid State Electrochem (in press), 2011) is senseless because there is no new aspect which is not also given in the paper of Ferse and Müller (J Solid State Electrochem (in press), 2011). All of the mentioned problems are already discussed and clarified in the publication by Ferse and Müller (J Solid State Electrochem (in press), 2011). The purely mathematical method is a possibility to obtain the concentration functions for the individual activity coefficients of the complementary ion species by factorizing a product function of the experimentally accessible concentration dependence of the mean activity coefficients to the required power.     

A note to the article “polarographic reduction of germanium” by A.K. Dasgupta and C.K.N. Nair

The nature of the two reduction waves of tetravalent germanium in ammonia-ammonium chloride buffer is described. Contrary to the statement of dasgup'ta and NAIR1 only the height of the first diffusion current should be used for analytical purposes. The second wave corresponds to a catalytic hydrogen evolution. The use of cthylenediaminetetra-acetic acid of pH 6–8 for the analysis of germanium is preferable².     

Green Procedure for the Synthesis of β-Nitro Sulfides by Michael Addition of Thiols to Nitroolefins

Michael addition of thiols to nitroolefins was carried out in water at room temperature without any catalyst, and β-nitro sulfides were obtained in excellent yields. This is the first example of Michael addition of thiols to nitroolefins in water without use of any catalyst. It provides a highly efficient, general, and practical green route to synthesis of β-nitro sulfides. Twenty-four new β-nitro sulfides were synthesized using this technique.     

Studies on the Performance and Structure of Supported Catalysts for the Partial Oxidation of Methane to Syngas

The catalytic properties of several supported metal catalysts on different carriers were studied in the partial oxidation of methane (POM) to syngas. In our experiment, supported noble metal catalysts exhibited better performance than the other supported transition metal catalysts. The catalyst performances were significantly influenced by the d-electron configuration of the active metal components and the dispersion of active metal components on the support. A catalyst with a moderate number of unpaired electrons in the d-orbital of the active metal support without obvious acidity or redox activity (e.g. MgO) was suitable for POM performance. The Rh/SiO2 catalyst was the best in the POM reaction, among those investigated. Reaction conditions apparently also affected the POM performance of the catalyst. The conversion of methane and the selectivity for CO increased with the reaction temperature, and a high CH4/O2 ratio was not beneficial for POM performance.     

Efficient three-step sequence for the deamination of α-aminoesters. Application to the synthesis of CysLT1 antagonists

A practical and efficient three-step sequence for the deamination of α-aminoesters is reported. This method is based on the NaBH₄-mediated selective reduction of α-diazoesters to α-hydrazonoesters and has been successfully applied to the deamination of several representative α-aminoesters including some l-cysteine ethyl ester derivatives, key intermediates in the synthesis of a series of CysLT1 antagonists.     

Comments on the Note on “Thermodynamic temperature differences from the ITS-90 for the correction of thermodynamic property data” by F. Pavese,P. Ciarlini,and P.P.M. Steur by J. Fischer,Chairman of WG4 of CCT

These are comments to a note from J. Fischer in publication.     

Search for approaches to improving the calculation accuracy of the protein—ligand binding energy by docking

The following reasons limiting the accuracy of calculations of the protein—ligand binding energy by the molecular docking programs are considered: the limited facilities of algorithms of finding a global minimum on a complicated multi-dimensional protein—ligand energy surface, restrictions on the degrees of freedom of a protein—ligand system including docking into a rigid protein, inadequacy of the existing force fields, a lack of taking into account the solvent or too rough allowance for the solvent in the docking procedure, a lack of the local energy optimization in the docking process, an inaccuracy of the construction of models of a target protein and a ligand, simplification of the calculation method of the Gibbs free energy of a molecular system, and limited computer resources for docking of one ligand. A new approach to the development of the new generation of docking programs is proposed. The approach allows one to remove step-by-step the existing simplifications and to increase considerably the accuracy of the whole docking process, including the calculation accuracy of the protein—ligand binding energy. The results of the study are presented and demonstrate the computational feasibility of the assigned docking problem.     

Cross-validation and evaluation of the performance of methods for the elemental analysis of forensic glass by μ-XRF, ICP-MS, and LA-ICP-MS

Elemental analysis of glass was conducted by 16 forensic science laboratories, providing a direct comparison between three analytical methods [micro-x-ray fluorescence spectroscopy (μ-XRF), solution analysis using inductively coupled plasma mass spectrometry (ICP-MS), and laser ablation inductively coupled plasma mass spectrometry]. Interlaboratory studies using glass standard reference materials and other glass samples were designed to (a) evaluate the analytical performance between different laboratories using the same method, (b) evaluate the analytical performance of the different methods, (c) evaluate the capabilities of the methods to correctly associate glass that originated from the same source and to correctly discriminate glass samples that do not share the same source, and (d) standardize the methods of analysis and interpretation of results. Reference materials NIST 612, NIST 1831, FGS 1, and FGS 2 were employed to cross-validate these sensitive techniques and to optimize and standardize the analytical protocols. The resulting figures of merit for the ICP-MS methods include repeatability better than 5 % RSD, reproducibility between laboratories better than 10 % RSD, bias better than 10 %, and limits of detection between 0.03 and 9 μg g^?1 for the majority of the elements monitored. The figures of merit for the μ-XRF methods include repeatability better than 11 % RSD, reproducibility between laboratories after normalization of the data better than 16 % RSD, and limits of detection between 5.8 and 7,400 μg g^?1. The results from this study also compare the analytical performance of different forensic science laboratories conducting elemental analysis of glass evidence fragments using the three analytical methods.

Studies on the Catalyst for Oxidation of o-Xylene to Phthalic Anhydride by the Image Texture Analysis Technique

The present paper covers surface texture features of the catalysts for the oxidation of o-xylene to phthalic anhydride (PA) investigated by the Image Texture Analysis Technique and obviously corresponding relationships between the catalyst activity and its texture features (entropy(F9) and angular second moment(F1)).By means of the two texture features(F9 and F1), the effects of promoters K2O and Al2O3 on the properties of the catalysts were analysed, a higher active catalyst' s surface texture model for active catalysts is given:d(F) = 0. 00693×F9 - 0. 98039×F1 - 0.03078 > 0The results show that the Image Texture Analysis Technique would be a useful tool for the studies of catalyst surface structure and computer-aided design of catalysts.     

Mechanisms for the Formation of Diamides and Polyamides by Aminolysis of d‐Glucaric Acid Esters

¹H and ¹³C NMR were employed to chart the conversion of the five‐membered lactone esters methyl d‐glucarate 1,4‐lactone (1) and ethyl d‐glucarate 6,3‐lactone (5) to N,N′‐dipropyl‐d‐glucaramide with n‐propylamine in DMSO‐d₆. These experiments were carried out to model the amide forming steps in polycondensation reactions between esterified d‐glucaric acid and diamines to give poly(d‐glucaramides). It was clear from the resulting NMR spectra that the lactones 1 and 5 were each converted in three consecutive steps to the product diamides; aminolysis of the lactone ester to the corresponding acyclic N‐propyl‐d‐glucaramide monoester, followed by lactonization to a five‐membered lactone amide, and concluding with aminolyis of the lactone amide to N,N′‐dipropyl‐d‐glucaramide (4). Comparison of the reaction pathways from 1 and 5 by ¹H NMR analysis suggests that ring opening of the 1,4‐lactone ester (1) and 1,4‐lactone amide (7) is faster than ring opening of the corresponding 6,3‐lactone ester (5) and 6,3‐lactone amide (3). Aminolysis of dimethyl l‐tartrate, which cannot form a five‐membered lactone, with n‐propylamine in DMSO‐d₆ was much slower than aminolysis of esterified glucaric acid, indicating that the lactone forming/lactone aminolysis steps are the dominant aminolysis rate enhancing steps from glucarate.     

A New Method for the Synthesis of Selenium Nanoparticles and the Application to Construction of H202 Biosensor

The well-distributed, stable selenium nanoparticles (10 nm) with good adhesive abilityand biocompatibility were successfully synthesized by using the template of chitosan cross-linkedwith glutaradehyde. The resulting selenium nanoparticles were used as a new carrier forhorseradish peroxidase to construct H2O2 biosensors with good performances.     

Applicability of Enzyme Columns Prepared by Co-Immobilising β-Glucuronidase and Arylsulfatase by the Sol-Gel Method for Deconjugation of Glucuronides and Sulfates in Urine

The paper describes the applicability of enzyme columns prepared by co-immobilising -glucuronidase and arylsulfatase in the pores of a sol-gel glass for deconjugation of urinary conjugates. After dialysing the crude Helix pomatia -glucuronidase/arylsulfatase preparation against PBS buffer the enzymes were co-entrapped without further purification steps in the sol-gel glass and the manually ground glass was packed into small glass columns.Urine samples spiked with 0.02–2 mM 4-nitrophenyl--D-glucuronide, 4-nitrophenyl sulfate, 4-methylumbelliferyl--D-glucuronide or 4-methylumbelliferyl sulfate were applied to the columns. Cleavage rates were determined by analysing the hydrolysis products 4-nitrophenol or 4-methylumbelliferone by high performance liquid chromatography. Quantitative hydrolysis of the conjugates investigated was reproducibly achieved within 10 minutes. Entrapment of the enzymes lead to an increased stability in organic solvents and a small shift in the pH optimum of enzyme activity. The columns could be used more than 170 times without loss of enzyme activity.     

New approach to the synthesis of an active substance of Agsular® pharmaceutical for the prevention and treatment of atherosclerosis

A new safe and technologically advantageous method to obtain an active substance of Agsular® pharmaceutical was developed. For the first time, potassium persulfate was used as a sulfating agent for polysaccharides. The structures, physicochemical properties, and anticoagulating and hypolipidemic activities of the Agsular® pharmaceutical ingredients obtained using different methods were studied in comparison.     

Application of gas-diffusion microextraction to the analysis of free and bound acetaldehyde in wines by HPLC–UV and characterization of the extracted compounds by MS/MS detection

In wines, the presence of high levels of acetaldehyde (AA) not only is responsible for undesirable characteristic odours but can also cause health adverse effects. Such sensorial activity of AA can be overcome by adding sulphites during winemaking, due to the formation of adducts between AA and sulphites, which lower the sensorial impact of AA. Nevertheless, bound AA can be released during wine storage; therefore, the knowledge of its total amount can be important to estimate the long-term wine quality. The proposed methodology is based on the extraction of AA from wines using gas-diffusion microextraction and determination by liquid chromatography. Free and bound forms of AA could be differentiated and determined using an alkaline hydrolysis step to dissociate the sulphites–AA adducts. This methodology was successfully applied to different wine types, with free AA values ranging between 5 and 26 mg L⁻¹ and total form between 154 and 906 mg L⁻¹. Bound AA was above 90% of the total content determined for all samples analysed, and higher amounts were obtained for white wines (around 98%). Other carbonyl compounds were also identified in the extracts using mass spectrometry.     

Sorption–Desorption of Copper and Strontium Ions by the Soil. The Influence of Microorganisms on the State of Metals

Sorption of heavy metal (copper and strontium) ions by the meadow chernozem and grey forest soils differing in the content of organic substance was described using the Langmuir equation. The analysis of characteristic sorption coefficients demonstrated that copper possesses the enhanced affinity for the studied soil samples compared to strontium. Maximal values of the sorption of copper (0.085 mmol/g) and strontium (0.045 mmol/g) obtained for the colloidal fraction of meadow chernozem soil (particle diameter d < 1 m) are approximately 1.5 times larger than for the same fraction of grey forest soil; this ratio remains almost the same even when using the coarser fraction (d < 50 m). It was established that up to 90% of metal ions could be present in the soil in an immobile form. An increase in the concentration of heavy metal ions in the soil causes their redistribution between the components of absorbing soil complex and an increase in the fraction of metal in mobile forms (water-soluble, exchange, soluble in weakly acidic medium). Upon the microbiological treatment (bioleaching in the suspension variant) of the soils containing copper or strontium ions, the total content of metal, including its mobile forms, decreases by an order of magnitude.     

Evaluation of ε for p-dinitrobenzene—aniline complexes by the Scott equation. Failure of the Benesi—Hildebrand equation

The Scott equation has been employed to determine ε for p-dinitrobenzene charge transfer complexes with anilines. It is seen that the Benesi—Hildebrand plots show a random scatter, whereas the Scott plots are satisfactory straight lines.