Selective para metalation of unprotected 3-methoxy and 3,5-dimethoxy benzoic acids with n-butyl lithium-potassium tert-butoxide (LIC-KOR): synthesis of 3,5-dimethoxy-4-methyl benzoic acid

The potassium salt of 3-methoxy and 3,5-dimethoxy benzoic acids undergoes deprotonation at the position para to the carboxylate group selectively when treated with LIC-KOR in THF at -78 degrees C and it has been extended to the synthesis of 3,5-dimethoxy-4-methyl benzoic acid. (C) 2000 Elsevier Science Ltd. All rights reserved.

Effect of Nanostructuring and Ex situ Amorphous Carbon Coverage on the Lithium Storage and Insertion Kinetics in Anatase Titania

Implications of nanostructuring and conductive carbon interface on lithium insertion/removal capacity and insertion kinetics innanoparticles of anatase polymorph of titania is discussed here.Sol-gel synthesized nanoparticles of titania (particle size similar to 6 nm) were hydrothermally coated ex situ with a thin layer of amorphous carbon (layer thickness: 2-5 nm) and calcined at a temperature much higher than the sol-gel synthesis temperature. The carbon-titania composite particles (resulting size similar to 10 nm) displayed immensely superior cyclability and rate capability (higher current rates similar to 4 g(-1)) compared to unmodified calcined anatase titania. The conductive carbon interface around titania nanocrystal enhances the electronic conductivity and inhibits crystallite growth during electrochemical insertion/removal thus preventing detrimental kinetic effects observed in case of unmodified anatase titania. The carbon coating of the nanoparticles also stabilized the titania crystallographic structure via reduction in the accessibility of lithium ions to the trapping sites. This resulted in a decrease in the irreversible capacity observed in the case of nanoparticles without any carbon coating.

REACTION OF THIOPHOSPHORYL FLUORIDE AND THIOPHOSPHORYL CHLORIDE WITH DIMETHYL SULPHOXIDE

Solid complexes of thiophosphoryl fluoride and thiophosphoryl chloride with dimethyl sulphoxide (DMSO) have been prepared and characterized.

Reaction of Thiophosphoryl Fluoride and Thiophosphoryl Chloride with Dimethyl Sulphoxide

Solid complexes of thiophosphoryl fluoride and thiophosphoryl chloride with dimethyl sulphoxide (DMSO) have been prepared and characterized.

Proton-bifurcated C-H center dot center dot center dot(O,O) hydrogen bonds in 2,3-dichloro-6-nitrobenzylaminium chloride

In the crystal structure of the title salt, C7H7Cl2N2O2+ center dot Cl-, the chloride anions participate in extensive hydrogen bonding with the aminium cations and indirectly link the molecules through multiple N+-H center dot center dot center dot Cl- salt bridges. There are two independent molecules in the asymmetric unit, related by a pseudo-inversion center. The direct intermolecular coupling is established by C-H center dot center dot center dot O, C-H center dot center dot center dot Cl and C-Cl center dot center dot center dot Cl- interactions. A rare three-center (donor bifurcated) C-H center dot center dot center dot (O,O) hydrogen bond is observed between the methylene and nitro groups, with a side-on intramolecular component of closed-ring type and a head-on intermolecular component.

Effect of V2O5 on the Surface and Structural Characteristics of Potassium Lithium Niobate

It has been suggested that materials with interesting and useful bulk non-linear optical properties might result by substituting vanadium, the lightest element in the group V of periodic table, for Nb or Ta atoms along with Li and three oxygens. It is with this motivation that we have been making attempts to grow single crystals of LiNbO3 doped with various concentrations of V2O5. Unfortunately the results obtained on the ceramic samples of this material have not been very encouraging, owing to their hygroscopic nature. However, our attempts to prepare both ceramic and single-crystalline samples of potassium lithium niobate (K3Li2Nb5O15; KLN) doped V2O5 were successful. In this letter we report the preliminary results concerning our studies on the effect of V2O5 doping on the structural as well as topographic features of both ceramic and single-crystalline samples of KLN.

Unfolding of Plasmodium falciparum triosephosphate isomerase in urea and guanidinium chloride solutions. Evidence for a novel disulfide exchange reaction in a covalently crosslinked mutant

The conformational stability of Plasmodium falciparum triosephosphate isomerase (TIMWT) enzyme has been investigated in urea and guanidinium chloride (GdmCl) solutions using circular dichroism, fluorescence, and size-exclusion chromatography. The dimeric enzyme is remarkably stable in urea solutions. It retains considerable secondary, tertiary, and quaternary structure even in 8 M urea. In contrast, the unfolding transition is complete by 2.4 M GdmCl. Although the secondary as well as the tertiary interactions melt before the perturbation of the quaternary structure, these studies imply that the dissociation of the dimer into monomers ultimately leads to the collapse of the structure, suggesting that the interfacial interactions play a major role in determining multimeric protein stability. The Cm(urea)/Cm(GdmCl) ratio (where Cm is the concentration of the denaturant required at the transition midpoint) is unusually high for triosephosphate isomerase as compared to other monomeric and dimeric proteins. A disulfide cross-linked mutant protein (Y74C) engineered to form two disulfide cross-links across the interface (13-74‘) and (13‘-74) is dramatically destablized in urea. The unfolding transition is complete by 6 M urea and involves a novel mechanism of dimer dissociation through intramolecular thiol−disulfide exchange.

Silicon tetrafluoride : Preparation and reduction with lithium aluminium hydride

Pure silicon tetrafluoride can be prepared in 66% yield from silicon tetrachloride by refluxing with lead fluoride in acetonitrile. The gas can be reduced to pure silane by lithium aluminum hydride in diethyl ether.

Nuclear-quadrupole resonance in coordination chemistry- identification of bridiging and therminal chlorines in the mercuric chloride-4-picoline n-oxide complex

The temperature dependence of the chlorine-35 n.q.r. in the mercuric chloride-4-picoline N-oxide complex has been studied from 77 K to room temperature, and the results are used to assign the observed frequencies to terminal and bridging chlorines.

New methods for the Preparation of Nitrosyl Chloride

A pure sample of nitrosyl chloride has been prepared either by reaction of phosphorus trichloride with concentrated nitric acid or by reaction of phosphorus trichloride with sodium nitrate in presence of water. The nitrosyl chloride gas has been characterized by i.r. spectral data and elemental analysis.