The volume and compressibility change for the formation of transition metal sulfate ion pairs at 25°C

The apparent molal volume and adiabatic compressibilities of some transition metal (Mn²⁺, Co²⁺ Ni²⁺, Cu²⁺, Zn²⁺, and Cd²⁺) sulfates have been determined at 25°C. Values of to 11.4 cm³-mole^–1 and to 31.3 × 10^–4cm³-mole^–1-bar^–1 at 1 atm were found for the formation of the transition metal sulfate ion pairs. These results are in good agreement with the values obtained from the high-pressure conductance measurements of Fisher et al., Shimizu et al., and Taniguchi et al. The volume and compressibility data indicate that 3.1±0.7 water molecules are lost when transition metals form ion pairs with SO ₄ ^2– . The fractions of inner-sphere ion pairs (20%) estimated in this study are in good agreement with the values obtained from ultrasonic measurements.     

Microwaves in organic synthesis. Thermal and non-thermal microwave effects

Microwave irradiation has been successfully applied in organic chemistry. Spectacular accelerations, higher yields under milder reaction conditions and higher product purities have all been reported. Indeed, a number of authors have described success in reactions that do not occur by conventional heating and even modifications of selectivity (chemo-, regio- and stereoselectivity). The effect of microwave irradiation in organic synthesis is a combination of thermal effects, arising from the heating rate, superheating or "hot spots" and the selective absorption of radiation by polar substances. Such phenomena are not usually accessible by classical heating and the existence of non-thermal effects of highly polarizing radiation--the "specific microwave effect"--is still a controversial topic. An overview of the thermal effects and the current state of non-thermal microwave effects is presented in this critical review along with a view on how these phenomena can be effectively used in organic synthesis.     

Free radical-scavenging activity of indolic compounds in aqueous and ethanolic media

Indolic compounds are a broad family of substances present in microorganisms, plants and animals. They are mainly related with tryptophan metabolism, and present particularities that depend on their respective chemical structures. The most important members of the family are the plant hormone, indole-3-acetic acid, and the animal hormone, melatonin. An important characteristic of some indolic compounds is that they may be useful as chemical preventive agents against diseases such as cancer, oxidative stress, etc. For this reason, the possible antioxidant activities (free radical-scavenging activity) of several indoles were studied. The2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid /H(2)O(2)/HRP decoloration method was applied to determine both hydrophilic (in buffered media) and lipophilic (in organic media) antioxidant properties of the indolic compounds. Also, a study of the hydrophilic antioxidant activities of indoles at different pH values (between 4.5 and 8.5) was made. Finally, their possible role as diet plant antioxidants is discussed.     

Quassinoids from Picrasma crenata

From woods of Picrasma crenata, a new stereoisomer dihydronorneoquassin was obtained together with others well knowns dihydronorneoquassin, parain, alpha-neoquassin, beta-neoquassin and quassin. The structures were determined by spectroscopic data and chemical evidence.     

Simple and rapid micellar electrokinetic capillary chromatographic method for simultaneous determination of four antiepileptics in human serum

A very rapid and simple MEKC method was developed for the simultaneous determination of four antiepileptic drugs, ethosuximide (Etho), primidone (Pri), phenytoin (Pht) and carbamazepine (Cbz) in human serum. Sample analysis required only 100 microL of human serum which only needed to be centrifuged, decanted and combined with the running buffer [5.3 mM Na(2)HPO(4)/3.2 mM borax buffer (pH 9.5) containing 55 mM SDS and 3.5% (v/v) acetone]. The analysis was performed in only 10 min into fused-silica capillaries (57 cm total length with 50 microm i.d. and 50 cm to the detector) using the MEKC methodology with diode-array detection at 220 nm. The calibration graphs were established for ethoximide, primidone, phenytoin and carbamazepine between 0 and 20 mg/L. Recoveries were between 85 and 87%. The simplicity of the proposed methodology makes it suitable for routine clinical use, especially for epileptic patients on polytherapy.     

Glycidol syntheses and valorizations: Boosting the glycerol biorefinery

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High resolution electrospray and electrospray tandem mass spectra of rotenone and its isoxazoline cycloadducts

An evaluation of the gas-phase ion chemistry of rotenone (1) by electrospray ionisation (ESI) mass spectrometry (MS) and tandem mass spectrometry (MS2) is presented, aiming at providing tools for its determination in natural and biological matrices. The behaviour of its cycloadducts with benzonitrile-N-oxide (2) and 2,4,6-trimethylbenzonitrile-N-oxide (3) was also evaluated and the MS data thus obtained have provided evidence into the mechanism of formation of the key product ion at m/z 192 which can be considered a marker in the MS and MS2 spectra of rotenone and its derivatives.     

Amide-water interactions in cosolvent systems. I. Solubilities and apparent molar volumes of methyl paraben

Solubility and apparent molar volume data are used to demonstrate effects of amide alkylation on amide-water interactions at 25° C. Precise measurements were made of the apparent molar volumes of the amides in binary amide-water mixtures using a dilatometric technique. The results show that the apparent molar volumes of alkyl-substituted amides in water pass through a minimum at an amide concentration which varies inversely with the degree of alkylation. Further studies showed that the solubilities of methyl paraben (methyl-p-hydroxybenzoate) and naphthalene in various amide-water solvent systems increased in characteristic fashion with amide alkylation.     

Novel heterocycle-based two-photon absorbing dyes

[structure: see text]. The synthesis and nonlinear optical characterization of two novel heteroaromatic-based chromophores is described. The new dyes present an A-pi-D-pi-A general framework, where A is a pi-deficient heteroaromatic ring (pyridine, quinoline, benzothiazole) and D a pi-excessive pyrrolyl moiety. Both systems exhibit large two-photon absorption (TPA) values in the femtoseconds regime (TPA cross section as high as 150 x 10(-50) cm(4) s photon(-1) molecule(-1) with 150 fs laser pulses). Their TPA-based optical limiting activity is also shown.     

Di­chloro­bis(1‐propyl­imidazolidine‐2‐thione‐κS)­cobalt(II)

The crystal structure of the title compound, [CoCl₂(C₆H₁₂N₂S)₂], consists of monomer units of a Co^II atom coordinated to two 1‐propyl­imidazolidine‐2‐thione ligands and to two chloride ions. The heterocyclic thione ligand is monodentate and coordinated to the metal through the thione S atom. The environment around the Co^II atom is a slightly distorted tetrahedron. The Co—S bond lengths are 2.341 (2) and 2.330 (2) Å, and the Co—Cl bond lengths are 2.234 (2) and 2.238 (2) Å. The most important point of distortion is the S—Co—S bond angle of only 97.83 (8)°. Intramolecular classical hydrogen bonds are found between the chloride ions and the N—H groups. Additionally, intra‐ and intermolecular non‐classical hydrogen bonds are found.