Effects of Micelles and Vesicles on the Oximolysis of p-Nitrophenyl Diphenyl Phosphate: A Model System for Surfactant-Based Skin-defensive Formulations against Organophosphates

The rates of oximolysis of p-nitrophenyl diphenyl phosphate (PNPDPP) by Acetophenoxime; 10-phenyl-10-hydi-oxyiminodecanoic acid; 4-(9-carboxynonanyl)-1-(9-carboxy-1-hydroyiminononanyl) benzene; 1-dodecyl-2-[(hydroxyimino)methyl]-pyridinium chloride (IV) and N-methylpyridinium-2-aldoxime chloride were determined in micelles of N-hexadecyl-N,N,N-trimethylammonium chloride (CTAC), N-hexadecyl-N,N-dimethylammonium propanesulfonate and dioctadecyldimethylammonium chloride (DODAC) vesicles. The effects of CTAC micelles and DODAC vesicles on the rates of oxymolysis of O,O-Diethyl O-(4-nitrophenyl) phosphate (paraoxon) by oxime IV were also determined. Analysis of micellar and vesicular effects on oximolysis of PNPDPP, using pseudophase or pseudophase with explicit consideration of ion exchange models, required the determination of the aggregate`s effects on the pK(a), of oximes and on the rates of PNPDPP hydrolysis. All aggregates increased the rate of oximolysis of PNPDPP and the results were analyzed quantitatively. In particular, DODAC vesicles catalyzed the reaction and increased the rate of oximolysis of PNPDPP by IV several million fold at pH`s compatible with pharmaceutical formulations. The rate increase produced by DODAC vesicles on the rate of oximolysis paraoxon by IV demonstrates the pharmaceutical potential of this system, since the substrate is used as an agricultural defensive agent and the surfactant is extensively employed in cosmetic formulations. (C) 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:1040-1052, 2009

Bichromophoric behavior of nitrophenyl-triazene anions: a resonance Raman spectroscopy investigation

Highly delocalized molecular frameworks with intense charge transfer transitions, known as push-pull systems, are of central interest in many areas of chemistry, as is the case of nitrophenyl-triazene derivatives. The 1,3-bis(2-nitrophenyl)triazene and 1,3-bis(4-nitrophenyl)triazene were investigated by electronic (UV-Vis) and resonance Raman (RR) spectroscopies. The bichromophoric behavior of 1,3-bis(4-nitrophenyl)triazene anion opens the possibility of tuning with visible radiation, two distinct electronic states. The RR profiles of nitrophenyl-triazene derivatives clearly show that the first allowed electronic state can be assigned to a charge transfer from the ring pi system to the NO2 moiety (ca 520 nm), while the second, as a charge transfer from N-3(-) to the aromatic ring (ca 390 nm). In the para-substituted derivative, a more efficient electron transfer and a greater energy separation between the two excited states are observed. Copyright (C) 2008 John Wiley & Sons, Ltd.

Room Temperature, Metal-Free Synthesis of Diaryl Ethers with Use of Diaryliodonium Salts

A fast, high-yielding synthesis of diaryl ethers with use of mild and metal-free conditions has been developed. The scope includes bulky ortho-substituted diaryl ethers, which are difficult to obtain by metal-catalyzed protocols. Halo-substituents, racemization-prone amino acid derivatives, and heteroaromatics are also tolerated. The methodology is expected to be of high utility in the synthesis of complex molecules and in the pharmaceutical industry.

Crown ethers : applications in inorganic synthesis

The ability of macroheterocyclic compounds to complex with ionic species has led to the synthesis and investigation of many multidentate macroheterocyclic species. The most stable complexes are formed between macrocyclic polyetheral ligands (crown ethers) with alkali or alkaline earth metal iona. There is an excellent correlation of the stability of these complexes with the size of the cation and the site of the cavity in the macrocyclic ligand. Additional factors, such as the basicity of the ligand and the solvating ability of the solvent, also play important roles in the stabilization of the complex. The stability of such complexes has been advantageously used to increase anionic reactivity and has been successfully applied to several organic fluorinations, oxidations, and similar reactions. The use of macrocyclic ligands in inorganic syntheses of otherwise difficult to obtain fluoro compounds has not been reported. O-carborane and m-carborane, C2BlOHl2, are icosahedral cage systems derived from Bl2H122- by replacement of BH with the isoelectronic CH group. These stable molecules exhibit electron-deficient bonding which can best be explained by delocalization of electrons. This delocalization gives rise to stability similar to that found in aromatic hydrocarbons. Crown ether activated potassium fluoride has been successfully employed in the conversion of alkyl, acyl and aryl halides to their respective fluorides. Analogously halide substituted carboranes were prepared, but their fluoro-derivatives were not obtained. The application of crown ethers in the synthesis of transition metal complexes is relatively unexplored. The usual synthesis of fluoro-derivative transition metal complexes involves highly reactive and toxic fluorinating agents such as antimony trifluoride, antimony penta fluoride. bromine trifluoride and hydrogen fluoride, An attempted preparation of the hexafluoroosmate (IV) ion via a crown activated, or naked fluoride~was unsuccessful. Potassium hexafluoroosmate (IV), K208F6. was eventually prepared using bromine trifluoride as a fluorinating and oxidizing agent .

Synthesis and characterization of a novel series of meso (nitrophenyl) and meso (carboxyphenyl) substituted porphyrins

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Kinetics of photoinduced birefringence in the guest-host system of poly(methyl methacrylate) doped with azobenzene-containing crown ethers

The kinetics of the buildup and decay of photoinduced birefringence was examined in a series of host-guest systems: azobenzene-containing crown ethers, differing in the size of the crowns, dissolved in a poly (methyl methacrylate) matrix. In all samples, the kinetics of the buildup of the birefringence was reasonably described by a sum of two exponential functions, the time constants being inversely proportional to the intensity of the pumping light and the magnitudes of the signals at the saturation level depending on the pumping light intensity and sample thickness. The dark decays were best described by the stretched exponential function, with the characteristic parameters (time constant and stretch coefficient) being practically independent of the type of crown ether. The time constants of the signal decay were orders of magnitude shorter than the respective constants of the dark isomerization of the azo crown ethers, thus indicating that the process controlling the decay was a relaxation of the polymer matrix and/or a rearrangement of the flexible parts of the crowns. (C) 2007 Wiley Periodicals, Inc.

Accumulation of semivolatile organic compounds in Antarctic vegetation: A case study of polybrominated diphenyl ethers

Antarctic plant communities are dominated by lichens and mosses which accumulate semivolatile organic compounds (SOCs) such as polybrominated diphenyl ethers (PBDEs) directly from the atmosphere. Differences in the levels of PBDEs observed in lichens and mosses collected at King George Island in the austral summers 2004-05 and 2005-06 are probably explained by environmental and/or plant parameters. Contamination of lichens showed a positive correlation with local precipitation, suggesting that wet deposition processes are a major mechanism controlling the uptake of most PBDE congeners. These findings are in agreement with physical-chemical data supporting that tetra- through hepta-BDEs in the Antarctic atmosphere are basically bound to aerosols. Conversely, accumulation of PBDEs in mosses appears to be controlled by other environmental factors and/or plant-specific characteristics. Model simulations demonstrated that an ocean-atmosphere coupling may have played a role in the long-range transport of less volatile SOCs such as PBDEs to Antarctica. According to simulations, the atmosphere is the most important transport medium for PBDEs while the surface ocean serves as a temporary storage compartment, boosting the deposition/volatilization ""hopping"" effect similarly to vegetation on continents. (C) 2011 Elsevier B.V. All rights reserved.

Positron scattering from the cyclic ethers oxirane, 1,4-dioxane, and tetrahydropyran

In this paper we report original measurements of total cross sections (TCSs) for positron scattering from the cyclic ethers oxirane (C2H4O), 1,4-dioxane (C4H8O2), and tetrahydropyran (C5H10O). The present experiments focus on the low energy range from similar to 0.2 to 50 eV, with an energy resolution smaller than 300 meV. This study concludes our systematic investigation into TCSs for a class of organic compounds that can be thought of as sub-units or moieties to the nucleotides in living matter, and which as a consequence have become topical for scientists seeking to simulate particle tracks in matter. Note that as TCSs specify the mean free path between collisions in such simulations, they have enjoyed something of a recent renaissance in interest because of that application. For oxirane, we also report original Schwinger multichannel elastic integral cross section (ICS) calculations at the static and static plus polarisation levels, and with and without Born-closure that attempts to account for the permanent dipole moment of C2H4O. Those elastic ICSs are computed for the energy range 0.5-10 eV. To the best of our knowledge, there are no other experimental results or theoretical calculations against which we can compare the present positron TCSs. However, electron TCSs for oxirane (also known as ethylene oxide) and tetrahydropyran do currently exist in the literature and a comparison to them for each species will be presented. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3696378]

Effect of some surfactants on the chemiluminescent reactions of bis(2,4,6-trichlorophenyl)oxalate and bis(2-nitrophenyl)oxalate with hydrogen peroxide

The chemiluminescent reactions of bis(2,4,6-trichlorophenyl)oxalate (TCPO) and bis(2-nitrophenyl)oxalate (2-NPO) with hydrogen peroxide in acetonitrile/water micellar systems (anionic, cationic, and non-ionic) and gamma-cyclodextrin were studied in the presence of fluoranthene or 9,10-diphenylanthracene, imidazole, and two buffer solutions, HTRIS+/TRIS and H2PO4-/HPO42-. The relative chemiluminenscence (CL) intensity is higher in the presence of the cationic (DDAB, CTAC, DODAC, and OTAC), anionic (SDS), and non-ionic (Tween 80) surfactants. In the presence of some non-ionic surfactants (Brij 35, Brij 76, and Tween 20), the CL intensity was partially quenched compared with the reaction with no surfactant. The sensitivity for hydrogen peroxide determination in the range 0.01 x 10(-4) to 1.0 x 10(-4) mol L-1, considering the slope of the calibration curves (maximum peak height of CL vs. concentration), improved with the introduction of DDAH, CTAB, and SDS in HTRIS+/TRIS buffer.

Kinetics and product distribution of p-nitrophenyl phosphate dianion solvolysis in ternary DMSO/alcohol/water mixtures are compatible with metaphosphate formation

The rate of solvolysis of p-nitrophenyl phosphate (PNPP) dianion in DMSO/water strongly decreases by increasing water concentration. Addition of linear alcohols (methanol, propanol, butanol, pentanol, and hexanol) at constant DMSO/water molar ratio produced an even sharper rate decrease. Alkyl phosphate formation, resulting from PNPP solvolysis in ternary DMSO/water/alcohol mixtures, increased with alcohol concentration and was essentially temperature independent. Methanol and hexanol were the poorest nucleophiles under all conditions. Activation energies and enthalpies for solvolysis in ternary mixtures were similar and entropies varied with alcohol concentration. Taken together these results can be best interpreted in terms of a dissociative mechanism with the intervention of metaphosphate. Copyright (C) 2011 John Wiley & Sons, Ltd.

5-(1-(4-phenyl)-3-(4-nitrophenyl)triazene)-10,15,20-triphenylporphyrin: a new triazene-porphyrin dye and its spectroelectrochemical properties

The new triazene-porphyrin dye 5-(1-(4-phenyl)-3-(4-nitrophenyl)triazene)-10,15,20-triphenylporphyrin, encompassing a reactive protonated triazene moiety, was prepared starting from meso-tetraphenylporphyrin (H2TPP), first converting it to the 5-(4-nitrophenyl)-10,15,20-triphenylporphyrin, then reducing to the 5-(4-aminophenyl)-10,15,20-tri(phenyl) porphyrin intermediate, and reacting with the diazonium salt of 4-nitroaniline; and characterized by spectroscopic and electrochemical methods. The absorption spectrum of the neutral species resembled the sum of H2TPP and of 1,3-bis(4-nitrophenyl) triazene spectrum, but the deprotonated anionic species showed more delocalized frontier orbitals, behaving as a push-pull system exhibiting triazenide-to-porphyrin charge-transfer transitions.

Cytotoxic diacetylenic spiroketal enol ethers from Plagius flosculosus

Three new diacetylenic spiroketal enol ethers named flosculins A (1), B (2), and C (3), along with five known compounds (4-8) of the same structural class, were isolated from the leaves of Plagius flosculosus. The structures were deduced by extensive 1D and 2D NMR spectroscopy and mass spectrometry. All isolated compounds exhibited significant cytotoxic activity against leukemia cells (Jurkat T and HL-60). Compounds 5-8 induced apoptosis in HL-60 cells with corresponding IC(50) values ranging from 4 to 6 microM.

Interesting results of catalytic hydrogenation of 3-(2-nitrophenyl)-isoxazoles and 3-(nitro-substituted-phenyl)-2-isoxazolines

The Pd-C-assisted hydrogenolysis of substituted 3-(2-nitrophenyl)-isoxazoles, irrespective of substitution on the isoxa-zole ring, invariably leads to reduction of nitro to amino group with concomitant regiospecific ring closure to yield substituted 4-quinolinamines. In contrast similar hydrogenation of 3-(nitro substituted phenyl)-2-isoxazolines results in reduction of the nitro group only with conservation of isoxazoline ring to yield 3-(amino substituted phenyl)-2-isoxazolines.

Temporal variations of perfluoroalkyl substances and polybrominated diphenyl ethers in alpine snow

The occurrence and temporal variation of 18 perfluoroalkyl substances (PFASs) and 8 polybrominated diphenyl ethers (PBDEs) in the European Alps was investigated in a 10 m shallow firn core from Colle Gnifetti in the Monte Rosa Massif (4455 m above sea level). The firn core encompasses the years 1997-2007. Firn core sections were analyzed by liquid chromatography-tandem mass spectrometry (PFASs) and gas chromatography-mass spectrometry (PBDEs). We detected 12 PFASs and 8 PBDEs in the firn samples. Perfluorobutanoic acid (PFBA; 0.3-1.8 ng L(-1)) and perfluorooctanoic acid (PFOA; 0.2-0.6 ng L(-1)) were the major PFASs while BDE 99 (