Activity coefficients of NaCl in the NaCl + NaBF4 + H2O ternary system at 298.15 K

The activity coefficients of sodium chloride in the NaCl + NaBF₄ + H₂O ternary system were experimentally determined at 298.15 K, at ionic strengths of 0.3. 0.5, 1, 2 and 3 mol kg⁻¹ from emf from the bi-ISE cell without liquid junction:

ISE-Na|NaCl(m_A), NaBF₄(m_B)|ISE-Cl

Quantum Defects as a Toolbox for the Covalent Functionalization of Carbon Nanotubes with Peptides and Proteins

Single‐walled carbon nanotubes (SWCNTs) are a 1D nanomaterial that shows fluorescence in the near‐infrared (NIR, >800 nm). In the past, covalent chemistry was less explored to functionalize SWCNTs as it impairs NIR emission. However, certain sp³ defects (quantum defects) in the carbon lattice have emerged that preserve NIR fluorescence and even introduce a new, red‐shifted emission peak. Here, we report on quantum defects, introduced using light‐driven diazonium chemistry, that serve as anchor points for peptides and proteins. We show that maleimide anchors allow conjugation of cysteine‐containing proteins such as a GFP‐binding nanobody. In addition, an Fmoc‐protected phenylalanine defect serves as a starting point for conjugation of visible fluorophores to create multicolor SWCNTs and in situ peptide synthesis directly on the nanotube. Therefore, these quantum defects are a versatile platform to tailor both the nanotube's photophysical properties as well as their surface chemistry.     

Complete assignment of the 1H and 13C NMR spectra of garciniaphenone and keto-enol equilibrium statements for prenylated benzophenones

This article reports the structural elucidation by IR, UV and MS spectroscopic data along with 1H and 13C NMR chemical shift assignments of two benzophenones isolated from the fruit pericarp of Garcinia brasiliensis Mart. (Clusiaceae): garciniaphenone, (1R,5S,7S)-3-benzoyl-4-hydroxy-6,6-dimethyl-5,7-di(3-methyl-2-butenyl)bicyclo[3.3.1]non-3-ene-2,9-dione, a novel triprenylated benzophenone; and 7-epi-clusianone, a tetraprenylated benzophenone that has already been extracted from another species of the same family. Furthermore, the keto-enol tautomeric equilibrium at solution-state was described for these compounds by 1D and 2D NMR spectral methods and one attempt to rationalize the different ratios between the noted tautomers was based on stereochemical features.     

Synthesis and characterization of polyesters derived from sebacic acid,hexanediol, and hydroquinone

Oils and fats derived from animals and plants provide a good renewable source for polymer precursors. In this investigation, fatty acids derived from plant oils and diols were used as monomers to produce polyesters by melt polycondensation. Sebacic acid, hexanediol, and hydroquinone were used as precursors in the polymer synthesis. The polymers were characterized by gel permeation chromatography, Fourier transform infrared spectroscopy, three-bending point flexural test, X-ray diffraction, tensile testing, and contact angle. The resulting polyesters were blended with epoxies to create materials with an increased elongation at break without affecting other mechanical properties.     

Unprecedented base effect on the synthesis of chiral phosphinate esters: A new route to P-chiral phosphine oxides of high enantiomeric purity

The stereochemical outcome of the reaction of chiral secondary alcohols with a phosphinyl chloride was found to be highly dependent on the achiral base used. Thus, the reaction of the readily available sugar derived carbinols, 1 and 2, with methylphenylphosphinyl chloride in the presence of triethylamine yields stereoselectively the corresponding Snp-phosphinates 3Sp and 5Sp in 94 and 92% diastereomeric excess (de). Simply changing the base from triethylamine to pyridine affords Rp-phosphinates 4Rp and 6Rp epimers to 3Sp and 5Sp at the phosphinyl phosphorus in 50 and 40% de respectively. These phosphinate esters were found to be good P-chiral transferring intermediates, they react with Grignard reagents under very mild conditions to give the corresponding phosphine oxides. Both enantiomers Sp- and Rp-o-anisylmethylphenylphosphine oxide (PAMPO) as well Sp- and Rp- methylphenylpropyl phosphine oxide were obained enantiomerically pure in high yields     

Synthesis and structure of the calixarene-like phosph(III)azane macrocycle [{P(mu-N(t)Bu)}2{1,5-(NH)2C10H6}]3

The reaction of [ClP(mu-NtBu)]2 with 1,5-diamino-naphthalene [1,5-(NH2)2C10H6] in Et3N-thf gives the trimeric macrocycle [{P(mu-NtBu)}2{1,5-(NH)2C10H6}]3(1); the X-ray structure of the toluene solvate 1.3toluene reveals a cone-shaped (calixarene-like) arrangement in which toluene guest molecules are trapped within the cavity.     

The folded, tetrameric phosph(III)azane macrocycle [(P(mu-NtBu))2(1,4-(NH)2C6H4)]4

The tetrameric macrocycle [(P(mu-NtBu))2(1,4-(NH)2C6H4)]4, obtained from the reaction of the phosphazane dimer [ClP(mu-NtBu)]2 with p-phenylenediamine, has an unusual folded conformation in the solid state and contains a roughly tetrahedral arrangement of endo N-H groups for the potential coordination of anions.     

Thermal behavior of verapamil hydrochloride and its association with excipients

The thermal properties of verapamil hydrochloride (VRP) and its physical association as binary mixtures with some common excipients were evaluated. Thermogravimetry (TG) was used to determine the thermal mass loss, as well as to study the kinetics of VRP thermal decomposition, using the Flynn-Wall-Ozawa model. Based on their frequent use in pharmacy, five different excipients (microcrystalline cellulose, magnesium stearate, hydroxypropyl methylcellulose, polyvinylpyrrolidone and talc) were blended with VRP. Samples were prepared by mixing the analyte and excipients in a proportion of 1:1 (m/m). DSC curves for pure VRP presented an endothermic event at 143 ± 2 °C (ΔH_melt = 132 ± 4 J g⁻¹), which corresponds to the melting (literature T_m = 143.7 °C, ΔH_melt = 130.6 J g⁻¹). Comparisons among the observed results for each compound and their binary physical mixtures presented no relevant changes. This suggests no interaction between the drug and excipient.     

Thermo‐oxidative degradation of HDPE as a function of its crystalline content

The composition, the thermal properties, and the kinetics of the thermo‐oxidative degradation of high‐density polyethylene (HDPE) were studied as a function of the increasing crystalline fraction, which resulted from the selective extraction of the amorphous part, through digestion by immersion in fuming nitric acid (HNO₃) for different periods of time. The chemical and thermodynamic changes in HDPE, brought about by digestion in nitric acid for different periods of time, are discussed. Changes in the chemistry and microstructure of the HDPE, as a function of acid treatment for different periods of time, were studied using infra‐red spectroscopy (FTIR), gel permeation chromatography (GPC), and thermal analysis (DSC and TGA), as well as scanning electron microscopy (SEM). These studies were carried out as a function of the extracted amorphous fraction of HDPE samples via digestion in HNO₃. These studies showed that in the first stages of the acid chemical attack, the amorphous part first undergoes a chemical modification and then dissolves into the strong acid medium. The total crystalline fraction apparently decreases during the first stages of the chemical attack and then increases as the amorphous part is extracted. TGA results show that as the selective extraction of the amorphous part occurs, there is a displacement of the thermo‐oxidative degradation toward higher temperatures. The kinetics of the thermo‐oxidative degradation as a function of the extraction of the amorphous part was followed according to the Horowitz‐Metzger method, and it was found that as the concentration of the crystalline fraction increases, the activation energy for the thermo‐oxidative degradation increases. SEM studies show that the extraction of the amorphous part does not affect the size of the crystalline lamellar thickness of HDPE. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1906–1915, 2009     

Synthesis of benzimidazo-substituted 3-quinolinecarboxylic acids as antibacterial agents

The 6- and 7-(1-ethylbenzimidazolyl)-substituted 1-ethyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acids were synthesized. Antibacterial activity was tested in vitro. Only one of the new compounds prepared showed slight antibacterial activity against one of the strains tested. So, they are of no interest as antibacterial agents.