Controversy on the Free Energy of Formation of CaO Additional Evidence in Support of Thermochemical Data

The standard free energies of formation of CaO derived from a variety of high-temperature equilibrium measurements made by seven groups of experimentalists are significantly different from those given in the standard compilations of thermodynamic data. Indirect support for the validity of the compiled data comes from new solid-state electrochemical measurements using single-crystal CaF2 and SrF2 as electrolytes. The change in free energy for the following reactions are obtained: CaO + MgF2 --> MgO + CaF2 Delta G degrees = -68,050 -2.47 T(+/-100) J mol(-1) SrO + CaF2 --> SrF2 + CaO Delta G degrees = -35,010 + 6.39 T (+/-80) J mol(-1) The standard free energy changes associated with cell reactions agree with data in standard compilations within +/- 4 kJ mol(-1). The results of this study do not support recent suggestions for a major revision in thermodynamic data for CaO.

Synthesis of novel disulfide containing macrocyclic diacylglycerols

New diacylglycerols (2-4) containing intramolecular disulfide linkages between pendant acyl chains were synthesized. Due to the differences in the location of disulfide units, the present method allows synthesis of macrocycles that vary in sizes. Copyright.

Novel Functionalised Troger's Bases: Synthesis of a New Class of Troger's Base Analogues Containing Dicarboxyl Functionality

The synthesis of three new Troger's base analogues, each functionalized with two carboxyl groups, is described. Copyright.

Synthesis and magnetic studies of flower-like nickel nanocones

Flower-like nickel nanocone structures are synthesized by a simple chemical reduction method using hydrazine hydrate as the reducing agent. The structure, morphology and magnetic properties of as synthesized products are studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and SQUID magnetometer. The morphology evolution is studied by varying the reaction temperature and concentration of nickel chloride keeping other conditions unchanged.

Synthesis and characterisation of heterometallic molecular triangles using ambidentate linker: self-selection of a single linkage isomer

The coordination driven self-assembly of discrete molecular triangles from a non-symmetric ambidentate linker 5-pyrimidinecarboxylate (5-pmc) and Pd(II)/Pt(II) based 90◦ acceptors is presented. Despite the possibility of formation of a mixture of isomeric macrocycles (linkage isomers) due to different connectivity of the ambidentate linker, formation of a single and symmetrical linkage somer in both the cases is an interesting observation. Moreover, the reported macrocycles represent the first example of discrete metallamacrocycles of bridging 5-pmc. While solution composition in both the cases was characterised by multinuclear NMR study and electrospray ionization mass spectrometry (ESI-MS), the identity of the assemblies in the solid state was established by X-ray single crystals structure analysis. Variable temperature NMR study clearly ruled out the formation of any other macrocycles by [4 + 4] or [2 + 2] self-assembly of the reacting components.

Directed Synthesis of Rocksalt AuCl Crystals

We report the first-time experimental realization of rocksalt AuCl crystals. Our approach involves Au(III) complexing and reduction to Au(I) using an amine-terminated surfactant in a low dielectric permittivity solvent. The low charge screening in nonpolar solvents promotes crystallization of rocksalt AuCl, in which the bonding is predominantly ionic, in preference over tetragonal AuCl. The rocksalt AuCl crystals obtained here will facilitate studies to unveil the nexus between electronic structure and crystal structure in AuCl polymorphs, and provide insights on these relationships in other polymorphic crystal systems. Our approach provides a new means for crystallizing selective polymorphs of inorganic compounds by subtly influencing the cation electronic structure by varying the dielectric permittivity of the synthesis medium. In addition, the AuCl crystals can serve as inexpensive Au(I) precursors for forming a variety of Au nanostructures.

Synthesis and magnetic studies of flower-like nickel nanocones

Flower-like nickel nanocone structures are synthesized by a simple chemical reduction method using hydrazine hydrate as the reducing agent. The structure, morphology and magnetic properties of as synthesized products are studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and SQUID magnetometer. The morphology evolution is studied by varying the reaction temperature and concentration of nickel chloride keeping other conditions unchanged.

Synthesis, crystal structures and protease activity of amino acid Schiff base iron(III) complexes

Iron(III) complexes, (NHEt3)[Fe(III)(sal-met)(2)] and (NHEt3)[Fe(III)(sal-phe)(2)], of amino acid Schiffbase ligands, viz., N-salicylidene-L-methionine and N-salicylidene L-phenylalanine, have been prepared and their binding to bovine serum albumin (BSA) and photo-induced BSA cleavage activity have been investigated. The complexes are structurally characterized by single crystal X-ray crystallography. The crystal Structures of the discrete mononuclear rnonoanionic complexes show FeN2O4 octahedral coordination geometry in which the tridentate dianionic amino acid Schiff base ligand binds through phenolate and carboxylate oxygen and imine nitrogen atoms. The imine nitrogen atoms are trans to each other. The Fe-O and Fe-N bond distances range between 1.9 and 2.1 angstrom. The sal-met complex has two pendant thiomethyl groups. The high-spin iron(III) complexes (mu(eff) similar to 5.9 mu(B)) exhibit quasi-reversible Fe(III)/Fe(II) redox process near -0.6 V vs. SCE in water. These complexes display a visible electronic hand near 480 nm in tris-HCl buffer assignable to the phenolate-to-iron(III) charge transfer transition. The water soluble complexes bind to BSA giving binding constant values of similar to 10(5) M-1. The Complexes show non-specific oxidative cleavage of BSA protein on photo-irradiation with UV-A light of 365 nm.

Synthesis, antimicrobial and cytotoxic activities of 1,3,4-oxadiazoles, 1,3,4-thiadiazoles and 1,2,4-triazoles

A new class of 1,3,4-oxadiazoles were prepared from acid hydrazides on treatment with different carboxylic acids in the presence of phosphorus oxychloride. Interconversion of oxadiazoles to thiadiazoles and triazoles was carried out with appropriate reagents. The antimicrobial and cytotoxic activities of compounds 7a-d to 12a-d were tested. Compounds 10d and 12d showed pronounced antimicrobial activity. Further, compound 10d exhibited maximum cytotoxicity. (C) 2008 Elsevier Masson SAS. All rights reserved.

Synthesis and Spectroscopic Investigations of Complexes of Lanthanide Nitrates with N-(4-Hethyl-2-Pyridyl)-Acetamide

New complexes of Lanthanide nitrates with N-(4-methyl-2-pyridyl)-acetamide (4-me-aapH) of the general formulae. [Ln(4-me-aapH)2] [NO3] (where Ln=La=La-Yb and Y)have been synthesized and haracterised by chemical analysis, molar conductivity and physical methods such as infrared, 13C NMR an electronic spectra in the visible region. Molar conductance and infrared data point to the presence to the coordinated nitrates groups. Infrared and 13C NMR data have been interpreted in terms of the coordination of the legand to the metal ion through the oxygen of the secondary amide and nitrogen of the hetrocyclic ring, in a bidentate fashion. Coordination number of ten seems probable for the complexes.

Unsteady Free-Convection Flow on a Rotating flat-Plate Under Nonuniform Gravity

The free convection problem with nonuniform gravity finds applications in several fields. For example, centrifugal gravity fieldsarisein many rotating machinery applications. A gravity field is also created artificially in an orbital space station by rotation. The effect of nonuniform gravity due to the rotation of isothermal or nonisothermal plates has been studied by several authors [l-5] using various mathematical techniques.

Studies in terpenoids. Part 42. Synthesis of 3-(2-hydroxyisopropyl)5,8-dimethyl-1,2-naphthoquinone (emmotin-H)

Emmotin-H, a naturally occurring sesquiterpenoid 1,2-naphthoquinone pigment (1) has been synthesised in a four step sequence starting from the known 5,8-dimethyl-4-oxotetralin-2-carboxylic acid (3a). Selenium dioxide oxidation of its methyl ester (3b) gives 3-methoxycarbonyl-5,8-dimethyl-1,2-naphthoquinone (4) which on reductive acetylation affords the corresponding diacetoxynaphthalene ester (5). Its reaction with excess of methylmagnesium iodide is accompanied by aerial oxidation during work-up and furnishes emmotin-H (1).

Dialkyl (3-Aryl- 1,2,4-oxadiazol-5-yl)phosphonates: Synthesis and Thermal Behavior-Evidence for Monomeric Alkyl Metaphosphate

Dialkyl (3-aryl-l,2,4-oxadiazol-5-yl)phosphonate6sa -h have been obtained by 1,3-dipolar cycloaddition of arenenitrile oxides 5a-f to dialkyl phosphorocyanidates (4a and 4b) in yields ranging between 30% and 58%. A standardized method for obtaining cyanidates 4a and 4b has been established. The diethyl thiophosphorocyanidate (4c) is less reactive than 4a and 4b, only the 3-(4'-nitrophenyl) derivative 6i being obtainable. While the IR and NMFt spectra of 6a-i were unexceptional, their UV spectra showed evidence of conjugative interaction in high degrees between the phosphonate and heterocyclic moieties as well as a varying conjugative interaction between the heterocyclic and aryl moieties. The oxadiazoles 6a-h are thermally labile and yield trialkyl phosphates 7 as the only identifiable products. A mechanism based on the intermediacy of monomeric alkyl metaphosphate 11 in the formation of trialkyl phosphate was postulated, and supportive evidence in the form of trapping the metaphosphate with acetophenone has been obtained.

Synthesis and characterization of a new sulphate derivative of hydrazine, N2H5HSO4

Hydrazinium(1 +) hydrogensulphate, N2H5HSO4, has been prepared for the first time by the reaction of solid ammonium hydrogensulphate with hydrazine monohydrate. The compound has been characterized by chemical analysis, infrared spectra, and X-ray powder diffraction. Thermal properties of N2H5HSO4 have been investigated using differential thermal analysis and thermogravimetric analysis and compared with those of N2H6SO4 and (N2H5)2SO4.