Systematization of types of triple bond

Summary All known compounds with a triple bond may be divided into two types. The first type consists of molecules and ions with the electronic configuration of a completed layer. The triple bond in these compounds has a high strength. The second type consists of molecules and ions formed by atoms that do not have p-orbitals and this causes the instability of this type of triple bond.I would like to thank V. N. Kondrat'ev and M. I. Vinnik for valuable comments.     

Factors affecting stability and equilibria of free radicals—IX: Non-equivalence of aryl groups in 1,1-diaryl-2-benzenesulphonyl-hydrazyls and related compounds

1,1-Bis-(3',5'-di-t-butylphenyl)-2-benzenesulphonyl-hydrazine 11 and the corresponding 2-picryl-hydrazine 13 were synthesized. Oxidation of 11 afforded the stable hydrazyl 12 whose ESR spectrum could be simulated in terms of three hyperfine coupling constants. These experimental data leave no alternative but to assign larger proton hyperfine coupling constants to one aryl group in 12 than to the other. This non-equivalence was interpreted in terms of the Linnett theory. The picrylhydrazyl 14 does not give completely resolved ESR spectra. Structures were ascertained by IR, UV-vis, ¹H NMR and ¹³C NMR spectra.     

Partitioning of pi-electrons in rings of polycyclic conjugated hydrocarbons. 5. Nonalternant compounds

All possible nonalternant hydrocarbons with a total of two, three, or four 5-, 6-, and 7-membered rings have been examined for the partition of their pi-electrons by averaging over all Kekulé structures (considered to contribute equally to the electron distribution) the pi-electrons in each ring in accordance to the rules introduced earlier: for each double bond shared with another ring one pi-electron is taken into account, and for double bonds that are not shared two pi-electrons are added. The trends observed for the partitions are discussed, and a comprehensive bibliography is provided as Supporting Information for all such systems, including both experimental and theoretical published data.     

Water-based drilling fluids: the contribution of xanthan gum and carboxymethylcellulose on filtration control

This study aimed mainly to evaluate the influence of xanthan gum (XG) and carboxymethylcellulose (CMC) in the filtration process of water-based drilling fluids, considering the conformational changes suffered by the polyelectrolyte with the addition of salt (NaCl) in different concentrations (0.17, 0.34 and 0.51 M). It was also evaluated the behavior of the fluid by the addition of calcite (calcium carbonate, CaCO₃). Sixteen drilling fluids were prepared with the same xanthan gum concentration (major application as thickener to transport the cuttings), but different salinities and having or not CMC and calcite at constant concentrations. This strategy was adopted to evaluate the real contribution of each additive in the control of filtration performance, frequently unclear in the papers. In general, the fluids prepared in all brines showed lower viscosities and higher filtrate loss compared to fluids of sweet water. This effect was more strong in fluids containing only XG. The addition of CMC enhanced the viscosity and reduced the filtrate loss. However, the best results were obtained when calcite was added. The results indicated that XG contribution as thickener is not enough to control efficiently the fluid filtration even in the presence of calcite. However, the addition of CMC and calcite to XG salt solution increased the viscosity and decreased significantly the filtrate loss. This result was attributed to synergistic interactions between XG, CMC and calcite.     

A method of testing thin webs in shear

This paper describes a method for measuring the shear strengths and moduli of foils, films, fabrics and papers as thin as a fraction of one mil. The technique involves the use of two steel loading plates, to which the edges of the specimen are adhesively bonded, and a stabilizing system which prevents the specimen from buckling before shear yield strengthis reached. The practicality of the method is demonstrated on aluminum foil, as thin as 0.9 mil, by duplicating handbook values. Repeatability of results is verified by scatter within 2 percent in strength and 4 percent in modulus. The applicability of this method to several boron and glass-fiber composites is then shown.     

Nanoscopic Imaging of meso‐Tetraalkylporphyrins Prepared in High Yields Enabled by Montmorrilonite K10 and 3 Å Molecular Sieves

We have developed a high‐yielding synthesis of meso‐tetraalkylporphyrins, which previously have been obtained only in lower yields. By employing Montmorrilonite K10 as the acid catalyst and 3 Å molecular sieves as the dehydrating agent, yields that reached 70 % could be achieved with some aliphatic aldehydes. The free‐base porphyrins with decyl ( C10 ) or longer chains were imaged at the single‐molecule level at the solvent/surface interface. Highly oriented pyrolytic graphite (HOPG) was used as a π‐stacking surface, whereas 1‐phenyloctane and 1‐phenylnonane were used as solvents. An odd–even effect was observed from C13 to C16 . For C13 a single‐crystal X‐ray structure allowed an unprecedented insight into how packing from two dimensions is expanded into a three‐dimensional crystal lattice.     

An Electrochemical Biosensor Platform for Testing of Dehydroepiandrosterone 3‐Sulfate (DHEA−S) as a Model for Doping Materials

Endogenous steroids such as dehydroepiandrosterone (DHEA) and dehydroepiandrosterone 3‐sulfate (DHEA?S) have commonly used as doping materials by athletes and to date novel techniques are needed for detection of these molecules. In this study, antibody‐based electrochemical biosensor has developed for testing level of the DHEA?S. For this aim, gold surfaces were initially modified with cysteamine (Cys) and then, DHEA?S antibody was immobilized on the surface via glutaraldehyde (GA) as a crosslinking agent. The stepwise modification of electrode surface was monitored by using various electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Linear range was determined as 2.5–100 ng/mL DHEA?S using differential pulse voltammetry (DPV) technique, as well. Moreover, repeatability (±S.D.), coefficient of variation (%) and limit of detection (LOD) values were calculated as 0.033, 1.030 and 3.971, respectively. Also, DHEA?S in synthetic serum and urine samples were successfully determined with standard addition method and confirmation analysis were performed with liquid chromatography quadrupole‐time of flight mass spectrometry (LC‐QTOF/MS) system. The selectivity was studied with the addition of some interfering molecules (testosterone, bovine serum albumin (BSA), cholesterol, uric acid, lactic acid, codein (COD), ascorbic acid, DHEA). Consequently, this work is proposed as practical, innovative and cost‐effective technique that can be easily adapted for the miniaturized form for the analysis of other doping substances as well as DHEA?S for the future works.     

in vitro Selection of Aptamer for Imidacloprid Recognition as Model Analyte and Construction of a Water Analysis Platform

Pesticide use in agriculture is one of the threats to water safety. Therefore, detection of pesticide residues is crucial for human health. Compared to conventional chromatographic methods, aptasensors are promising tools for fast, cheap and sensitive detection of environmental contaminants. To the best of our knowledge, such an aptasensor has not been reported for imidacloprid (Imi) which is one of the most widely used pesticides. In order to meet this demand, we initially selected two novel aptamers designated as ‘Apta‐1’ and ‘Apta‐2’ by graphene oxide‐SELEX (GO‐SELEX) method. Then, these aptamers were used to fabricate the gold electrode‐based aptasensor platforms and characterized by using electrochemical methods such as cyclic voltammetry, and electrochemical impedance spectroscopy as well as X‐Ray photoelectron spectroscopy. It was found that the limit of detection value of Apta‐1 based sensor for the Imi was found better than Apta‐2 based system, although linear ranges were similar. Based on that finding, Apta‐1 based system was further tested against possible interference molecules. The proposed platform was successfully used for detection of very low concentrations of Imi in the range of ng/mL. Thus, it eliminates the need for sample pre‐treatment and enables a practical analysis in real wastewater samples.