Study on Isoelectric Point of Magnesium Aluminum Hydroxide

Isoelectricpoint(IEP)valuesareInaiulyforbytheprOpeniesandcomposihonOfmetalions,thcyindicaethemagnitudeofrmnityofmetalionsf0releCtrn.TheeffodofIEPofmagncsiumabonumhydroaldeonthepropeniesandcomposihonofmetalionsarediscussedinthispaPer.Experimentall.PreparationofmagnesiumaltalnumhydrokidePOsihvesol.ThepreParationmethodreferredtoref[41.2.MeasurementS0ftheelmphoreticmobilityTheelectrophorehcmobilihesweredetetrinedwithDXD-IIm0delInieroelCCtfophoresisapparatUs.at1hei0nicstrengthof0.OOland…     

Is Universal,Simple Melting Point Prediction Possible?

An investigation of the melting points of 520 organic 1:1 salts is presented with the aim of developing a universal, simple, physically well-founded prediction scheme. The general reliability and reproducibility of the recorded experimental data are discussed with respect to purity, phase behavior, disorder and thermal history of a given substance. Additionally, mistakes, systematic errors, or lack of conventions can lead to considerable differences in the experimental measurements. A rough error bar for the reproducibility of the melting points of organic salts of ±5 to ±15 °C can be assigned. With this restraint, we developed two simple, semiempirical, five- and nine-parameter schemes with easy-to-calculate quantities. With these, we could predict the melting temperature of a given organic salt in the temperature range of -25 to +300 °C with an average error of 33.5 °C and a relative error of 9.3%. All calculated quantities are assessed with the help of conventional DFT, COSMO and COSMO-RS calculations, and are currently implemented into the IL-Prop module of the upcoming version of COSMOtherm. These prediction schemes are suitable for high-throughput computational screening of substances in the context of "computer-aided synthesis". Therefore, they are valuable tools to find a compound with a suitable melting point before its first synthesis.     

Efficient Method for the Synthesis of Benzimidazoquinazoline Derivatives with Three‐Point Diversity

An efficient strategy for the preparation of a novel heterocyclic ring system of benzimidazoquinazolines with three‐point diversity has been described. The compounds were obtained by treating o‐phenylene diamines with o‐nitrobenzaldehyde to give benzimidazoles, followed by reduction of the nitro group to give an amine. Derivatization of the resulting amine with isothiocyanates followed by in situ cyclodesulfurization at rt furnished the title compounds in high yields and purities.     

The Isoelectric Point and the Points of Zero Charge of Fe-Al-Mg Hydrotalcite-like Compounds

The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc,which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations.     

Criticism on Jäntti's Three Point Method on Curtailing Gas Adsorption Measurements

Jäntti introduced a method to reduce the time required for the stepwise measurement of adsorption isotherms (Jäntti et al., Progress in Vacuum Microbalance Techniques, Vol. 1, Heyden, London, pp. 345–353, 1972). After a pressure change he measured the adsorbed mass three times and calculated its equilibrium value for the new pressure. In the present paper we discuss the applicability of this method in a broader scope (without starting from a single combination of gas and solid adsorbent) and also discuss the influence of measurement inaccuracies. It is shown that the method can serve as an early warning system, which decides whether an improvement of the adsorption model is necessary.     

The Effect of Added Salts and Organics on the Cloud Point of TX‐114

Herein we report the effect of additives (salts and organics) on the cloud point (CP) of nonionic surfactant Triton X‐114 (TX‐114) aqueous solutions. CP showed a concentration dependent variation in the absence of any added compound. Addition of quaternary ammonium (or phosphonium) bromides to 0.8 mM TX‐114 solutions increased the CP. It was found that long chain alcohols and amines decreased the CP of 0.8 mM TX‐114 +80 mM Bu₄AmB aqueous system, while it either remained constant or increased in the presence of short chain additives. The effect of first group additives (long chain) can be explained by considering that these additives solubilize in interfacial region and assist in micellar growth. Short chain additives remain in aqueous phase and affect the micelle hydration by affecting the solvent. Pentylamine behaved differently than pentanol: pentylamine increased the CP (like short chain additives) while pentanol decreased the CP. In pentylamine, the hydrophilicity of NH₂ group and its dissociation into NH₃ ⁺ dominates over the hydrophobicity of its alkyl chain. Aliphatic hydrocarbons first decreased and then increased the CP. The overall behavior depended upon the chain length of the hydrocarbon. With decane, the CP decreasing region disappeared completely.     

Point group symmetries of the molecular orbitals of HD+ beyond the Born–Oppenheimer approximation

The isotope shifts of the electronic states of HD⁺ are calculated, for the first time, within an adiabatic MO-LCAO theory. A typical heteronuclear C_∞v correlation diagram comes out, obeying conservation of point group orbital symmetries and noncrossing rule.     

Speciation of Chromium in Water Samples by Cloud Point Extraction Combined with Low Temperature Electrothermal Vaporization ICP‐OES

Abstract

A new method based on cloud point extraction (CPE) separation and electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV‐ICP‐OES) detection was proposed for the determination of chromium species. Thenoyltrifluoracetone (TTA) was used as both an extractant for CPE of Cr(III) and a chemical modifier for ETV‐ICP‐OES determination. When the system temperature is higher than the cloud point temperature (CPT) of the selected surfactant, Triton X‐114, the complex of Cr(III) with TTA could enter the surfactant‐rich phase, whereas the Cr(VI) remained in aqueous solutions. Thus, an in situ separation of Cr(III) and Cr(VI) could be realized. The concentrated analyte was introduced into ETV‐ICP‐OES for determination of Cr(III) after proper disposal. Cr(VI) is reduced to Cr(III) prior to determining total Cr, and its assay is based on substracting of Cr(III) from total chromium. The main factors affecting cloud point extraction and the vaporization behavior of the analyte were investigated in detail. Under the optimized conditions, the limit of detection (LOD) for Cr(III) was 0.22 µg/L by preconcentration of a 10 mL sample solution, and the relative standard deviation (RSD) was 3.8% (C_Cr(III)=0.5 µg/mL, n=5). The proposed method was applied to the speciation of chromium in different water samples. In order to verify the accuracy of the method, a certified reference water sample was analyzed, and the results obtained were in good agreement with certified values.     

Determination of Trace Amounts of Nickel (Ⅱ) by Graphite Furnace Atomic Absorption Spectrometry Coupled with Cloud Point Extraction

A new method based on the cloud point extraction(CPE) for separation and preconcentration of nickel(Ⅱ) and its subsequent determination by graphite furnace atomic absorption spectrometry(GFAAS) was proposed, 8-hydroxyquinoline and Triton X-100 were used as the ligand and surfactant respectively. Nickel(Ⅱ) can form a hy-drophobic complex with 8-hydroxyquinoline, the complex can be extracted into the small volume surfactant rich phase at the cloud point temperature(CPT) for GFAAS determination. The factors af...     

The Cloud Point Behaviors and the Liquid–Liquid Equilibrium of L31—Inorganic Sodium Salt Aqueous Two-Phase Systems

The cloud point (CP) of triblock-copolymer L31 aqueous solution was determined with salting-out salts (Na₂SO₄/Na₂CO₃/NaF/NaCl/NaBr). The results show that all these salts can decrease the CP of L31 aqueous solution and form aqueous two-phase system (ATPS). With increasing concentrations of Na₂SO₄ and Na₂CO₃, an obvious phase inversion could be observed and phase inversion points were found. This was mainly due to the change in density, the salt-rich phase shifted from the top phase to the bottom phase. Meanwhile, the liquid-liquid equilibrium (LLE) data for L31-Na₂SO₄/Na₂CO₃/NaF/NaCl/NaBr ATPSs were measured at 288.15 K. The salt ability to decrease the CP and to induce the phase separation is as follows: Na₂SO₄?>?Na₂CO₃, NaF?>?NaCl?>?NaBr. Finally, the order of anions that reduced the CP and caused phase separation was obtained as follows: SO₄^2? >CO₃^2?, F^??>?Cl^??>?Br^?.     

Investigation of the Chemical Action of the Gliding and “Point” Arcs Between the Metallic Electrode and Aqueous Solution

The plasma–solution interaction processes for gliding and point arcs between the aqueous solution surface and the metal electrode in the gas phase are studied. The plasma, liquid, and surface zones are taken into consideration. The electric field strength is measured, and the gas and electron temperatures and ion composition are estimated for the plasma zone. The cathode fall, water vaporization rate, and active species current yield due to the radiation chemistry mechanism are determined for the surface zone. The efficiency of oxidation of iodine ions and organic dyes by different types of discharge in the liquid zone are investigated. The difference in action of the various discharge types may be connected with various influences of the plasma and surface zone on the oxidation processes.     

Determination of Mecruy at Trace Level in Natural Water Samples by Hydride Generation Atomic Absorption Spectrophotometry after Cloud Point Extraction Preconcentration

Mercury as a heavy metal of high toxicity is one of the most harmful elements to human beings and other creatures. Since mercury concentration in natural water is low, proper preconcentration techniques are required to increase its concentration, lower it…     

Determination of Ultratrace Amounts of Copper（ Ⅱ ） in Water Samples by Electrothermal Atomic Absorption Spectrometry After Cloud Point Extraction

IntroductionIn environment, copper is usually found in traceor ultratrace levels, and its detection requires sensitiveinstrumental measuring techniques such as electrother-mal atomic absorption spectrometry(ETAAS) and ICP-AES or ICP-MS. Frequently, a prec…     

Are Point Mutations in HMG-CoA Reductases (Hmg1 and Hmg2) a Step towards Azole Resistance in Aspergillus fumigatus?

Invasive aspergillosis, mainly caused by Aspergillus fumigatus, can lead to severe clinical outcomes in immunocompromised individuals. Antifungal treatment, based on the use of azoles, is crucial to increase survival rates. However, the recent emergence of azole-resistant A. fumigatus isolates is affecting the efficacy of the clinical therapy and lowering the success rate of azole strategies against aspergillosis. Azole resistance mechanisms described to date are mainly associated with mutations in the azole target gene cyp51A that entail structural changes in Cyp51A or overexpression of the gene. However, strains lacking cyp51A modifications but resistant to clinical azoles have recently been detected. Some genes have been proposed as new players in azole resistance. In this study, the gene hmg1, recently related to azole resistance, and its paralogue hmg2 were studied in a collection of fifteen azole-resistant strains without cyp51A modifications. Both genes encode HMG-CoA reductases and are involved in the ergosterol biosynthesis. Several mutations located in the sterol sensing domain (SSD) of Hmg1 (D242Y, G307D/S, P309L, K319Q, Y368H, F390L and I412T) and Hmg2 (I235S, V303A, I312S, I360F and V397C) were detected. The role of these mutations in conferring azole resistance is discussed in this work.     

Point by point comparison of two thermosensitive polymers exhibiting a similar LCST: is the age of poly(NIPAM) over?

The present Communication compares the thermosensitivity in dilute aqueous solutions of well-defined copolymers composed of 95% of 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA) and 5% of oligo(ethylene glycol) methacrylate (OEGMA, Mn = 475 g.mol-1) and poly(N-isopropylacrylamide) (PNIPAM) samples having similar degrees of polymerization and chain-ends. The thermoresponsive behavior of P(MEO2MA-co-OEGMA) was found to be overall comparable, and in some cases, superior to PNIPAM. Hence, P(MEO2MA-co-OEGMA) copolymers can be considered as ideal structures, which combine both the properties of poly(ethylene glycol) and PNIPAM in a single macromolecule.     

How Does Peripheral Functionalization of Ruthenium(II)–Terpyridine Complexes Affect Spatial Charge Redistribution after Photoexcitation at the Franck–Condon Point?

Ruthenium polypyridine‐type complexes are extensively used sensitizers to convert solar energy into chemical and/or electrical energy, and they can be tailored through their metal‐to‐ligand charge‐transfer (MLCT) properties. Much work has been directed at harnessing the triplet MLCT state in photoinduced processes, from sophisticated molecular architectures to dye‐sensitized solar cells. In dye‐sensitized solar cells, strong coupling to the semiconductor exploits the high reactivity of the (hot) singlet/triplet MLCT state. In this work, we explore the nature of the ¹MLCT states of remotely substituted Ru^II model complexes by both experimental and theoretical techniques. Two model complexes with electron‐withdrawing (i.e. NO₂) and electron‐donating (i.e. NH₂) groups were synthesized; these complexes contained a phenylene spacer to serve as a spectroscopic handle and to confirm the contribution of the remote substituent to the ¹MLCT transition. [Ru(tpy)₂]²⁺‐based complexes (tpy=2,2′:6′,2′′‐terpyridine) were further desymmetrized by tert‐butyl groups to yield unidirectional ¹MLCTs with large transition dipole moments, which are beneficial for related directional charge‐transfer processes. Detailed comparison of experimental spectra (deconvoluted UV/Vis and resonance Raman spectroscopy data) with theoretical calculations based on density functional theory (including vibronic broadening) revealed different properties of the optically active bright ¹MLCT states already at the Franck–Condon point.     

Studies on Immunoglobulin G in Human Sera from Guillain Barre Syndrome Patient (Ⅱ)——The Determination of the Isoelectric Point of Immunoglobulin G by Capillary Isoelectric Focusing

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Cooperative Catalysis of Metal and O?H⋅⋅⋅O/sp3‐C?H⋅⋅⋅O Two‐Point Hydrogen Bonds in Alcoholic Solvents: Cu‐Catalyzed Enantioselective Direct Alkynylation of Aldehydes with Terminal Alkynes

Catalyst–substrate hydrogen bonds in artificial catalysts usually occur in aprotic solvents, but not in protic solvents, in contrast to enzymatic catalysis. We report a case in which ligand–substrate hydrogen‐bonding interactions cooperate with a transition‐metal center in alcoholic solvents for enantioselective catalysis. Copper(I) complexes with prolinol‐based hydroxy amino phosphane chiral ligands catalytically promoted the direct alkynylation of aldehydes with terminal alkynes in alcoholic solvents to afford nonracemic secondary propargylic alcohols with high enantioselectivities. Quantum‐mechanical calculations of enantiodiscriminating transition states show the occurrence of a nonclassical sp³‐C? H???O hydrogen bond as a secondary interaction between the ligand and substrate, which results in highly directional catalyst–substrate two‐point hydrogen bonding.