A combined experimental and computational approach was used to distinguish between different polymorphs of the pharmaceutical drug aspirin. This method involves the use of abinitio random structure searching (AIRSS), a density functional theory (DFT)-based crystal structure prediction method for the high-accuracy prediction of polymorphic structures, with DFT calculations of nuclear magnetic resonance (NMR) parameters and solid-state NMR experiments at natural abundance. AIRSS was used to predict the crystal structures of form-I and form-II of aspirin. The root-mean-square deviation between experimental and calculated 1H chemical shifts was used to identify form-I as the polymorph present in the experimental sample, the selection being successful despite the large similarities between the molecular environments in the crystals of the two polymorphs. 相似文献
The present paper is a continuation of comprehensive study regarding to synthesis and properties of pyrazoles and their derivatives. In its framework an experimental and theoretical studies of thermal decomposition of the 3,3-diphenyl-4-(trichloromethyl)-5-nitropyrazoline were performed. It was found, that the decompositions of the mentioned pyrazoline system in the solution and at the melted state proceed via completely different molecular mechanisms. These mechanisms have been explained in the framework of the Molecular Electron Density Theory (MEDT) with the computational level of B3LYP/6-31G(d). A Bonding Evolution Theory (BET) examination of dehydrochlorination of the 3,3-diphenyl-4-(trichloromethyl)-5-nitropyrazoline permits elucidation of the molecular mechanism. It was found, that on the contrary for most known HCl extrusion processes in solution, this reaction is realised via single-step mechanism. 相似文献
The inhibitory action of cupric ions in the process of radiation polymerization of acrylic acid (AA) in aqueous solution was investigated as well as the reaction of the products of gamma radiolysis of water with polyacrylic acid (PAA) in the presence of cupric ions. In the case of AA-CuSO4 and PAA-CuSO4 systems irradiated at 77 K an external protective effect caused by copper ions was observed. This effect was connected with the electron transfer between a radical and the Cu2+ ion. During radiolysis of copper arcylate (A2Cu) and a system AA-A2Cu in aqueous solutions a protective effect exerted by copper ions was observed which seemed to be connected with the dispersion of the absorbed radiation energy by the groups: copper-ligands. 相似文献
Soluble products obtained from the oxidation of four types of coal, each characterised by different degree of coalification
and different degree of sulphur content, are studied. The coals are oxidised with peracetic acid (PAA) and nitric acid. Analyses
are performed by Atmospheric Pressure-Temperature Programmed Reduction (AP-TPR) and Fourier Transform Infrared Spectroscopy
(FTIR). The soluble products contain much more sulphur than the insoluble products of oxidation. The products obtained from
the reaction with HNO3 contain higher amounts of inorganic sulphur compounds, while those obtained from the reaction with PAA are characterised
by an increased content of organic sulphur species. 相似文献
The title compound, C14H20O2, adopts a conformation in which the δ‐valerolactone and cyclohexane rings are almost coplanar with one another. The γ‐methyl substituent occupies an axial position with respect to the cyclohexane ring. The δ‐valerolactone moiety adopts an envelope arrangement, while the cyclohexane ring exists in a chair conformation. 相似文献
3H-1,2-Benzoxathiole 2,2-dioxides (benzosultones) undergo thermal extrusion of sulfur dioxide to form ortho-quinone methides that enter Diels-Alder reaction with maleimides to form chroman 2,3-dicarboxylic acid derivatives. 相似文献
Nickel-ruthenium alloys with various compositions have been deposited by electrodeposition for the first time. Cyclic voltammetry and linear stripping voltammetry measurements show that codeposition of nickel with ruthenium is possible below the potential value of nickel reduction. High-quality alloys containing nickel and ruthenium can be plated at cathodic potentials ranging from − 0.5 to − 1.0 V vs SCE. Deposited coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The diffractograms obtained show that an increase of nickel concentration in alloy will lead to a change in the phase composition and formation of NiRu (100) and (101) phases which is observed to be 78 mas.% Ni. SEM studies confirm the surface homogeneity and presence of small, regular grains. AFM observation allows the estimation of the real surface area of obtained alloys which increase with more negative electrodeposition potentials. Ni-Ru alloys were found to be highly electroactive in the water splitting process, which can be connected with the presence of the NiRu phase and a well-developed electroactive area.
Electrochemical deposition of Ni-Ru alloys with various composition and their catalytic activity in water splitting process
The polarographic behaviour of 2-nitronaphthalene was investigated by DC tast polarography (DCTP) and differential pulse polarography (DPP), both at a dropping mercury electrode, and differential pulse voltammetry and adsorptive stripping voltammetry, both at a hanging mercury drop electrode. Optimum conditions have been found for the determination of 2-nitronaphthalene by the given methods in the concentration ranges of 2×10–6–1×10–4, 2×10–7–1×10–4, 1×10–8–1×10–4 and 2×10–9–1×10–8 M, respectively. Practical applicability of these techniques was demonstrated by the determination of 2-nitronaphthalene in drinking and river water after its preliminary separation and preconcentration using liquid–liquid and solid-phase extraction with limits of determination of 3×10–10 M (drinking water) and 3×10–9 M (river water). 相似文献
The oxazole yellow dye, YOYO-1 (a symmetric homodimer), is a commonly used molecule for staining DNA. We applied the brightness analysis to study the intercalation of YOYO-1 into the DNA. We distinguished two binding modes of the dye to dsDNA: mono-intercalation and bis-intercalation. Bis-intercalation consists of two consecutive mono-intercalation steps, characterised by two distinct equilibrium constants (with the average number of base pair per binding site equals 3.5): and , respectively. Mono-intercalation dominates at high concentrations of YOYO-1. Bis-intercalation occurs at low concentrations. 相似文献
Colloidal noble metal-based nanoparticles are able to catalyze oxidation of chromogenic substrates by H2O2, similarly to peroxidases, even in basic media. However, lack of robust chromogens, which work in high pH impedes their real applications. Herein we demonstrate the applicability of selected catechol derivatives: bromopyrogallol red (BPR) and pyrogallol (PG) as chromogenic substrates for peroxidase-like activity assays, which are capable of working over wide range of pH, covering also basic values. Hyperbranched polyglycidol-stabilized gold nanoparticles (HBPG@AuNPs) were used as model enzyme mimetics. Efficiency of several methods of improving stability of substrates in alkaline media by means of selective suppression of their autoxidation by molecular oxygen was evaluated. In a framework of presented studies the impact of borate anion, applied as complexing agent for PG and BPR, on their stability and reactivity towards oxidation mediated by catalytic AuNPs was investigated. The key role of high concentration of hydrogen peroxide in elimination of non-catalytic oxidation of PG and improvement of optical properties of BPR in alkaline media containing borate was underlined. Described methods of peroxidase-like activity characterization with the use of BPR and PG can become universal tools for characterization of nanozymes, which gain various applications, among others, they are used as catalytic labels in bioassays and biosensors. 相似文献