Penta­chloro‐1,3,6‐tris­(diethyl­phenyl­phosphino)­dirhenium(II,III)

The title complex [systematic name: penta­chloro‐1κ³Cl,2κ²Cl‐tris(diethylphenylphosphino)‐1κP,2κ²P‐dirhenium(II,III)(Re—Re)], 1,3,6‐Re₂Cl₅(PEt₂Ph)₃ or [Re₂Cl₅(C₁₀H₁₅P)₃], consists of dirhenium mol­ecules with eclipsed structures similar to those of previously characterized 1,3,6‐Re₂Cl₅(PR₃)₃ compounds. The Re—Re bond distance is 2.2262 (3) Å and the metal–metal bond order is 3.5.     

Factors influencing the autoxidation of fatty acids: effect of olefin geometry of the nonconjugated diene

Autoxidations of cis,cis, cis,trans, and trans,trans nonconjugated octadecadienoates and pentadecadienes were carried out in the presence of alpha-tocopherol to investigate the effect of olefin geometry on this oxidation process and provide insight into the factors that influence the autoxidation of fatty acids. We have found that as the trans character of the diene increases, the amount of O(2) trapping at the central (bis-allylic) position of the pentadienyl radical also increases. In addition, the rate constant for beta-fragmentation (k(beta) approximately 10(6) s(-1)) of the bis-allylic peroxyl radical decreased on going from the cis,cis to the trans,trans diene. We have also found that for the cis,trans nonconjugated dienes, there is a preference for trapping of the pentadienyl radical by O(2) at the transoid end, generating the cis,trans conjugated hydroperoxide as the major product.     

Synthesis and characterization of surrogate nuclear explosion debris: urban glass matrix

Journal of Radioanalytical and Nuclear Chemistry - We report a study of a fast radiochemical method to determine the activity of 131I via the radiochemical recovery obtained with a 129I tracer....     

Local remeshing for large amplitude grid deformations

Fluid-structure interaction (FSI) modelling can involve large deformations in the fluid domain, which could lead to degenerating mesh quality and numerical inaccuracies or instabilities, if allowed to amplify unchecked. Complete remeshing of the entire domain during the solution process is computationally expensive, and can require interpolation of solution variables between meshes. As an alternative, we investigate a local remeshing algorithm, with two emphases: (a) the identification and remedy of flat, degenerate tetrahedra, and (b) the avoidance of node motion, and hence associated interpolation errors.Initially, possible topological changes are examined using a dynamic programming algorithm to maximise the minimum local element quality through edge reconnection. In the 3D situation it was found that reconnection improvements tend to be limited to long edges, and those with few (three or four) element neighbours. The remaining degenerate elements are classified into one of four types using three proposed metrics – the minimum edge-to-edge distance (EE), the minimum node-to-edge distance (NE), and the shortest edge length (SE) – and removed according to the best manner for their type. Optimised thresholds for identifying and classifying elements for removal were found to be EE < 0.18, NE < 0.21, SE < 0.2.     

TiO2ZrO2 composite: Synthesis,characterization and application as a facile,expeditious and recyclable catalyst for the synthesis of 2-aryl substituted benzoxazole derivatives

The activity of an efficient mesoporous TiO₂ZrO₂ composite catalyst for the synthesis of 2-aryl substituted benzoxazole derivatives using 2-aminophenol and substituted benzaldehydes/heterocyclic aldehydes at moderate temperature was studied. The catalyst was prepared by a co-precipitation method and characterized by X-ray diffraction, BET surface area and scanning electron microscopy. The effect of temperature, solvents and catalyst concentration on the synthesis of benzoxazole derivatives was systematically investigated. Short reaction times, green-reaction profiles, good to excellent yields, reliable cost efficiency, simple workup conditions and reusability of an eco-friendly catalyst are the noteworthy highlights of the reported method. The catalyst could be easily recovered and reused several times without any significant loss in the yield. The use of the present catalytic system to mediate the title chemical synthesis in a synthetic operation is important for the development of new atom-economic strategies and this is efficient in building complex structures from simple starting materials in an environmentally benign fashion.     

Direct observation of ion evaporation from a triply charged nanodroplet

Triply charged, highly solvated metal ions of the form [Ln(H(2)O)(n)](3+) can be generated using a commercial mass spectrometer, and CID studies on these highly charged metal-solvent clusters allow for the direct observation of a process best described as ion evaporation.     

Affine Systems: Asymptotics at Infinity for Fractal Measures

We study measures on ℝ ^d which are induced by a class of infinite and recursive iterations in symbolic dynamics. Beginning with a finite set of data, we analyze prescribed recursive iteration systems, each involving subdivisions. The construction includes measures arising from affine and contractive iterated function systems with and without overlap (IFSs), i.e., limit measures μ induced by a finite family of affine mappings in ℝ ^d (the focus of our paper), as well as equilibrium measures in complex dynamics. By a systematic analysis of the Fourier transform of the measure μ at hand (frequency domain), we identify asymptotic laws, spectral types, dichotomy, and chaos laws. In particular we show that the cases when μ is singular carry a gradation, ranging from Cantor-like fractal measures to measures exhibiting chaos, i.e., a situation when small changes in the initial data produce large fluctuations in the outcome, or rather, the iteration limit (in this case the measures). Our method depends on asymptotic estimates on the Fourier transform of μ for paths at infinity in ℝ ^d . We show how properties of μ depend on perturbations of the initial data, e.g., variations in a prescribed finite set of affine mappings in ℝ ^d , in parameters of a rational function in one complex variable (Julia sets and equilibrium measures), or in the entries of a given infinite positive definite matrix.      

A facile and expeditious approach for the synthesis of 2-azetidinone derivatives via a multicomponent reaction

Abstract  

New organic reactions allow chemical transformations which were previously unknown. Therefore, new reactions are important contributions to progress in the field of organic synthesis. Herein, we are reporting a simple, one-pot, efficient three-component synthesis of novel 3-chloro-4-[4-(2-oxo-2H-chromen-4-ylmethoxy)phenyl]-1-phenylazetidin-2-one derivatives using 4-(2-oxo-2H-chromen-4-ylmethoxy)benzaldehydes, anilines, and chloroacetyl chloride in the presence of triethyl amine as a catalyst under different conditions. Taking into account environmental and economic considerations, the protocol presented here has the merits of simple operation, convenient work-up, being environmentally benign, and providing good yields. The synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR, MS, and elemental analysis.