Solvatochromic behavior of dyes with dimethylamino electron‐donor and nitro electron‐acceptor groups in their molecular structure

Six dyes with N,N‐dimethylaminophenyl and 4‐nitrophenyl or 2,4‐dinitrophenyl groups in their molecular structures were prepared and characterized. These compounds have different conjugated bridges (C?C, C?N, and N?N) connecting the electron‐donor and the electron‐acceptor groups. All compounds are solvatochromic, with reverse solvatochromism occurring. The solvatochromic band observed in each spectrum for the dyes is due to a π ? π* transition, of an intramolecular charge transfer nature, which occurs from the electron‐donor N,N‐dimethylaminophenyl group to the electron‐acceptor group in the molecules, which is reinforced by the structures of the compounds optimized by applying density functional theory, which exhibit high planarity. The reverse solvatochromism was explained considering two resonance structures. The benzenoid form is better stabilized in less polar solvents and characterizes the region displaying positive solvatochromism, while the dipolar form is better stabilized in more polar solvents, in the region of negative solvatochromism. The Catalán multiparametric approach was used to study the contribution of solvent acidity, basicity, dipolarity, and polarizability to the solvatochromism exhibited by the compounds. These compounds are good candidates for the investigation of the polarizability and, to a lesser extent, the dipolarity of the medium, with very little interference from specific interactions of the solvent through hydrogen bonding. Copyright © 2014 John Wiley & Sons, Ltd.     

Preconcentration procedure for determining trace amounts of Ni,Cd, Pb and Cu in high-salinity waters after cloud-point extraction

A procedure for determination of Cd, Pb, Cu and Ni in high-salinity waters by inductively coupled plasma optical emission spectrometry has been developed. It is based on cloud-point extraction of these metals as complexes of diethyldithiocarbamate (NaDDTC) in micellar media of non ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114). Multivariate optimisation techniques have been applied to optimise the experimental variables. A full two-level factorial design was used to evaluate the influence of variables and Doehlert design was performed to find the optimum values. The effect of interference from residual salinity in surfactant-rich phase was also investigated. The developed procedure allows to achieve enhancement factors of 20.0, 20.4, 19.5 and 20.6, along with limits of detection (3σ _B) of 0.030, 2.1, 0.62 and 0.27 µg L^?1, and precision expressed as relative standard deviation (%RSD, n = 10) of 3.7 (40.0 µg L^?1), 5.7 (20.0 µg L^?1), 6.6 (20.0 µg L^?1) and 3.1% (10.0 µg L^?1) for Cd, Pb, Cu and Ni, respectively. The accuracy was evaluated by spike tests on the seawater (salinity of 35‰) and petroleum produced formation waters (salinity between 15‰ and 75‰). It was obtained by recoveries between 79% and 105%.     

Solute–Solvent Interactions from Diffusion of Flavonoids in Methanol

The diffusion coefficients of five commercial flavonoids in methanol were determined at 25°C utilizing the Taylor–Aris dispersion technique. The results provide insight on solute–solvent interactions, in particular, on subtle differences in hydrogen bonding of the various hydroxyl groups of these compounds with the solvent.     

Kinetics of methylation of a solvatochromic vinylogous α‐pyridone in different solvents

The kinetics of the reaction with iodomethane of the solvatochromic dye 4‐[2‐(N‐methyl‐4,6‐diphenylpyridiniumyl)]phenoxide 2, generated in situ from the corresponding N‐methyl‐2,4‐diphenyl‐6‐(4‐hydroxyphenyl)pyridinium salt 4, was studied in various solvents and solvent mixtures, in search of a possible correlation between its reactivity and solvatochromism in solution. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 819–825, 1999     

Stereochemistry and some synthetic uses of the heteroarylation of phospholes

Further studies have been conducted on the condensation of electron-rich arenes or heteroarenes with the dienic system of phosphole P-complexes. According to the X-ray crystal structure analysis of one of the resulting 2-aryl-3-phospholene P-complexes, the condensation takes place on the side of the diene opposite to the complexing group. The decomplexation of the phospholene P–Mo(CO)₅ and P–W(CO)₅ complexes, respectively, by reaction with sulfur or halogens and tertiary amines yields the corresponding P-sulfides and oxides with full retention of the stereochemistry at phosphorus. Double condensation of the phosphole P-complexes onto the 2 and 5 positions of thiophene and furan ultimately leads to phosphole–thiophene–phosphole and phosphole–furan–phosphole chains. The first type has been characterized by X-ray crystal structure analysis of its P,P-disulfide. No electronic delocalization appears to take place along the chain.     

Water-in-Oil-in-Water Double Emulsions as Protective Carriers for Sambucus nigra L. Coloring Systems

The use of natural colorants is needed to overcome consumer concerns regarding synthetic food colorants′ safety. However, natural pigments have, in general, poor stability against environmental stresses such as temperature, ionic strength, moisture, light, and pH, among others. In this work, water-in-oil-in-water (W₁/O/W₂) emulsions were used as protective carriers to improve color stability of a hydrophilic Sambucus nigra L. extract against pH changes. The chemical system comprised water and corn oil as the aqueous and oil phases, respectively, and polyglycerol polyricinoleate (PGPR), Tween 80, and gum Arabic as stabilizers. The primary emulsion was prepared using a W₁/O ratio of 40/60 (v/v). For the secondary emulsion, W₁/O/W₂, different (W₁/O)/W₂ ratios were tested with the 50/50 (v/v) formulation presenting the best stability, being selected as the coloring system to test in food matrices of different pH: natural yogurt (pH 4.65), rice drink (pH 6.01), cow milk (pH 6.47), and soy drink (pH 7.92). Compared to the direct use of the extract, the double emulsion solution gave rise to higher color stability with pH change and storage time, as corroborated by visual and statistical analysis.     

Degradation of the insecticide parathion in methanol by gamma-irradiation

The gamma-radiation from⁶⁰Co was used to induce parathion degradation in methanol solution, and the resulting products were quantified by GC-NPD and identified by GC-MS. The insecticide was completely degraded (99%) in methanol after treatment with 30 kGy doses at a dose rate of 3.12 kGy h⁻¹. The metabolites detected after radiolysis were p-aminophenol, paraoxon and aminoparathion, but no p-nitrophenol. The parathion radiation yield (G-parathion) in methanol solution was also calculated.     

Alkylation et acylation d'acridanones-9

N-Alkylations and N-acylations of 9-acridanones substituted in position 2 or 3 by nitro and methoxy groups are described. Physical characteristics of the new compounds so obtained are given.