Unexpected formation of N,N-disubstituted formamidines from aromatic amines, formamides and trifluoroacetic anhydride

An intriguing selectivity towards the formation of the formamidine was observed upon the reaction of an amine with sodium hydride and trifluoroacetic anhydride in dimethyl formamide. Various aromatic amines were reacted with a series of N,N-disubstituted formamides as a solvent under the influence of trifluoroacetic anhydride to thoroughly probe this behaviour. A trend in selectivity is discussed and a proposed mechanism for the reaction is also presented.     

Optimal stopping problems by two or more decision makers: a survey

A review of the optimal stopping problem with more than a single decision maker (DM) is presented in this paper. We classify the existing literature according to the arrival of the offers, the utility of the DMs, the length of the sequence of offers, the nature of the game and the number of offers to be selected. We enumerate various definitions for this problem and describe some dynamic approaches. Fouad Ben Abdelaziz is on leave from the Institut Superieur de Gestion, University of Tunis, Tunisia e-mail: foued.benabdelaz@isg.run.tn.     

Hydroformylation of Olefins Catalyzed by Rhodium Trichloride Anchored on Ti-HMS

Rhodium trichloride supported on Ti-hexagonal mesoporous silica (Ti-HMS), via a bipyridyl group, is an efficient catalyst for the hydroformylation of olefins at 120 °C and 40.8 atm of CO/H₂ (CO/H₂=2/1). The catalyst is selective leading to high ratios of linear or branched aldehydes from functionalized olefins, and high activity in the case of propene which gave a turnover frequency of 6209 mol/mol(Rh)/h.     

Elaboration,Characterization and Thermal Decomposition Kinetics of New Nanoenergetic Composite Based on Hydrazine 3-Nitro-1,2,4-triazol-5-one and Nanostructured Cellulose Nitrate

This research aims to develop new high-energy dense ordinary- and nano-energetic composites based on hydrazine 3-nitro-1,2,4-triazol-5-one (HNTO) and nitrated cellulose and nanostructured nitrocellulose (NC and NMCC). The elaborated energetic formulations (HNTO/NC and HNTO/NMCC) were fully characterized in terms of their chemical compatibility, morphology, thermal stability, and energetic performance. The experimental findings implied that the designed HNTO/NC and HNTO/NMCC formulations have good compatibilities with attractive characteristics such as density greater than 1.780 g/cm³ and impact sensitivity around 6 J. Furthermore, theoretical performance calculations (EXPLO5 V6.04) displayed that the optimal composition of the as-prepared energetic composites yielded excellent specific impulses and detonation velocities, which increased from 205.7 s and 7908 m/s for HNTO/NC to 209.6 s and 8064 m/s for HNTO/NMCC. Moreover, deep insight on the multi-step kinetic behaviors of the as-prepared formulations was provided based on the measured DSC data combined with isoconversional kinetic methods. It is revealed that both energetic composites undergo three consecutive exothermic events with satisfactory activation energies in the range of 139–166 kJ/mol for HNTO/NC and 119–134 kJ/mol for HNTO/NMCC. Overall, this research displayed that the new developed nanoenergetic composite based on nitrated cellulose nanostructure could serve as a promising candidate for practical applications in solid rocket propellants and composite explosives.     

Crystal Structure,Thermal Analysis and IR Spectroscopic Investigation of Bis Benzyl Ammonium Monohydrogentetraoxoarsenate(V) Monohydrate

Abstract  

The salt bis benzyl ammonium monohydrogentetraoxoarsenate(V) monohydrate [C₆H₅CH₂NH₃ ⁺]₂HAsO₄ ²⁻·H₂O, M = 373.92, Triclinic, P−1. a = 6.514(1), b = 8.910(2), c = 15.061(3) ?, α = 99.26(2), β = 93.93(1), γ = 97.64(1)°, V = 851.5(3), Z = 2, D _x  = 1.460, λ (MoKα) = 0.71073 ?, μ = 0.99 mm⁻¹, F(000) = 126, T = 20(2)  °C, final R = 0.673 for 5488 unique reflections. Planes of HAsO₄ ²⁻ alternate with planes of C₆H₅CH₂NH₃ ⁺ groups. The structure consists of infinite parallel two-dimensional planes built of mutually connected ions and water molecules by strong O–H···O and N–H···O hydrogen bonding. There are no contacts other than van der Waals interactions between the layers. Differential scanning calorimetry study on bis benzyl ammonium monohydrogentetraoxoarsenate(V) monohydrate was carried out. The infrared of polycrystalline samples of this compound have been recorded at room temperature.     

Design and Synthesis of New Differentiated Concurrent Mono‐ and Tridentate Ligands (Tectons) Based on Pyridine,Terpyridine, and Dihydrooxazole Units

The design, synthesis, and characterization of the 10 linear and bent acentric ligands 1 – 10 (tectons) based on the differentiation of two divergently disposed coordinating poles is reported. The nature of the two poles and their distance are varied by the use of different linear spacers. For these molecules, a monodentate coordinating site, i.e., a pyridine ring, and a tridentate coordinating site, i.e., a pyridine moiety bearing at the 2 and 6 positions either two thioether groups or two dimethylamino units (PySMe and PyN(Me₂)₂ type, resp.), a terpyridine, or a pyridine ring bearing two optically pure dihydrooxazole units, are combined.     

Nano‐emulsion use for the synthesis of polyaniline nano‐grains or nano‐fibers

We report that nano‐emulsions can be creatively used as a morphology selective synthesis method to prepare not only nano‐grains but also nano‐fibers with high selectivity. Synthesis of the two different morphological materials was demonstrated using polyaniline synthesis as a model case. Polyaniline nano‐grains were synthesized from aniline molecules in nano‐size aqueous droplets as polymerization sites whose droplets were generated by inverse water‐in‐oil nano‐emulsion use, and polyaniline nano‐fibers were synthesized from aniline in aqueous nano‐dimensional channels as polymerization sites whose channels were generated by direct oil‐in‐water nano‐emulsion use containing high population of oil droplets. Using the approaches, we successfully synthesized nano‐fibers of 60 nm diameter with 0.5 µm length and also nano‐grains having diameter of 60–80 nm. The two different polymerization sites of nano‐scale dimension were made by changing the ratio among surfactant, aqueous aniline/HCl solution, and oil, i.e. organic solvent. We found the nano‐fibers synthesized from the channels formed by the direct oil‐in‐water nano‐emulsion have higher bulk electrical conductivity than the nano‐grains which were synthesized from the droplets formed by the inverse water‐in‐oil emulsion. We also found that the emulsion use allows us to use a room temperature synthesis unlike conventional synthesis methods which require to use ice bath temperature. Physical properties of both nano‐fibers and nano‐grains synthesized were characterized by Fourier transform infrared (FTIR), UV–Vis spectra, scanning electron microscopy (SEM), and four probes conductivity measurement. Copyright © 2009 John Wiley & Sons, Ltd.