Dry Inert Atmosphere Research Articles

Rapid, clean and efficient one-pot synthesis of thiopyrano[2,3-b]quinolines via domino Michael addition/cyclization reactions

Rapid and efficient one-pot synthesis of thiopyrano[2,3-b]quinolines is described from the reaction of 3-formyl-quinoline-2-thiones with acrylonitrile using economical organic base Et3N at room temperature. The reaction proceeded smoothly via domino Michael addition/cyclization reactions and did not require dry solvent, inert atmosphere and column chromatography purifications.

Enantioselective Organocatalytic Synthesis of 5 and 6 Membered Heterocycles

During last decade the field of Organocatalysis emerged as one of the cornerstones of organic asymmetric synthesis. The use of organocatalysis has some advantages such as metal free reactions, environmentally friendly conditions, does not need to use dry solvents or inert atmosphere, avoid the use of protecting groups, etc … For these reasons, several research groups have focused their efforts on the development of new organocatalytic methodologies that render the final products in excellent yields and stereoselectivities. Concretely, the organocatalytic synthesis of 5 and 6 membered heterocycles has attracted much attention. In this review we have the aim to describe the different organocatalytic methodologies developed since in the synthesis of 5 and 6 heterocycles. Keywords: Organocatalysis, Michael reaction, 3+2 cycloaddition, diels-Alder, domino reaction, heterocylic rings, organic chemistry, Synthesis of Azacycles, Pyrrolidines, Saturated Heterocycles, Nitrogen, addition-cyclization, 1,3-dipolar cycloaddition, nitroaldehydes, homoproline derivatives

Structure and superconducting properties of nonstoichiometric YBa2Cu3O y annealed at 300°C in a dry argon atmosphere

Using the full-profile X-ray analysis of diffraction lines, the behavior of YBa2Cu3Oy nonstoichiometric ceramics upon annealing at 300°C in a dry inert atmosphere has been investigated. It has been established that, in the YBa2Cu3O6.3 sample with the initial tetragonal structure, this treatment leads to nucleation of an orthophase with a low degree of rhombicity, which becomes prevailing after annealing for 56 h. In this case, superconductivity with an initial temperature of the transition of ∼50 K occurs in the sample. In the YBa2Cu3O6.7 sample with the initial orthorhombic structure, the orthophase with a somewhat enhanced rhombicity arises during annealing and becomes prevailing after annealing for 56 h; in this case, Tc of the system grows from 57 to 63 K. Data of the magnetic measurements for both cases can be interpreted as the presence of two orthorhombic phases with different temperatures of transition to the superconducting state in the samples after annealing.

A novel high performance stopped-flow apparatus equipped with a special constructed mixing chamber containing a plunger under inert condition with a very short dead-time to investigate very rapid reactions

The present work set out to establish a novel stopped-flow instrument equipped with a special constructed mixing chamber containing a plunger to enable a kinetic study of the very rapid reactions under a dry inert atmosphere glove bag, in particular, for the reactions are sensitive to moisture or air. A stopped-flow spectrophotometer is essentially a conventional spectrophotometer with the addition of a system for rapid mixing of solutions. The purpose of this work is to describe the fabrication and evaluation of specially constructed and in-expensive stopped-flow system. The evaluation includes determination of the dead-time, relative mixing efficiency, and the measurement of known rate constants. Herein, a dead-time of about 3.4ms was determined in the final modified construction of the stopped-flow apparatus in order to investigate the rapid initial during which some form of reaction intermediate is presented to be formed.

Establishing a new conductance stopped-flow apparatus to investigate the initial fast step of reaction between 1,1,1-trichloro-3-methyl-3-phospholene and methanol under a dry inert atmosphere

In the present work, for the first time, investigation of the initial fast step of reaction between 1,1,1-trichloro-3-methyl-3-phospholene (TCMP) and methanol was studied under a dry inert atmosphere by a newly constructed CSF apparatus by means of a further development in the configuration of the previous stopped-flow spectrophotometer (SFS). Hence, it was necessary to make many changes to the stopped-flow apparatus: replacement of the spectrophotometer amplifier with a conductance amplifier and the use of a conductivity cell to replace the optical one. The conductivity cell was made of polyethylene capillary tube (1 mm internal diameter; i.d.) and its inside dimensions were 1 mm i.d. × 3 mm long. Two tube electrodes which are made of stainless steel (0.8 mm i.d. × 14 mm long) were fixed at opposite ends of the observation cell and their outer surfaces were connected to the conductivity bridge amplifier by the two lead wires. The mixer was a 3-way Teflon valve and the distance between the mixer and the end of the observation cell was 30 mm. For each run, at least 24 µL of solution was required for a typical trace with a dead time of about 5 ms. Because of the extreme sensitivity of TCMP to moisture, the stopped-flow (CSF) apparatus was used inside a glove bag under a dry nitrogen atmosphere. Kinetic parameters for pseudo first-order reaction involving k(obs) = 30 s(-1) at 22 °C and activation energy E(a) = 13.55 KJ mol(-1) were successfully calculated for the initial fast step of the reaction between TCMP and methanol at 22 °C.

SYNTHESIS AND CONFORMATIONS OF p-(ACETAMIDO)-BUTOXYCALIX[4]ARENE AND p-(BENZAMIDO)-BUTOXYCALIX[4]ARENE

The conversion of p-(amino)butoxycalix[4]arene, 1, to p-(acetamido)butoxy-calix[4]arene, 2, and p-(benzamido)butoxycalix[4]arene, 3, via acetylation and benzoylation reactions, respectively have been conducted. The acetylation reactions was conducted by reflux method and room temperature method. The reflux method was conducted by refluxed a solution of 1 and acetic anhydride in acetic acid glacial solvent for 12 hours to result 2 in 53.8% yield; while the room temperature method was conducted by stirred a solution of 1, acetyl chloride, and dry pyridine in dry toluene solvent and inert atmosphere at room temperature for 24 hours to result 2 in 97.8% yield. By the room temperature method and using benzoyl chloride, the compound 3 was obtained in 67.1% yield. Structures of the both compounds were confirmed using IR, 1H NMR, and 13C NMR spectroscopy methods. Pursuant to the 1H-NMR spectral patterns of their bridge methylene and calix aryl protons, they were known that the compound 3 exist in partial cone conformation; whereas the compound 2 exist in partial cone, cone, and 1,2-alternate conformations where the partial cone was the main conformer. Keywords: p-(amino)butoxycalix[4]arene, p-(acetamido)butoxycalix[4]arene, p-(benzamido)butoxycalix[4]arene,

Brève. Analyse des fluctuations respiratoires : vers une nouvelle approche statistique dans l’évaluation du contrôle de l’asthme ?

Corrosive wear due to oxygen and/or moisture in the air is shown to be a major form of gear failure. Using a Micro-Ryder Gear Tester, it is shown that with diester-based lubricants, damage is worse in air than in a dry inert atmosphere at low loads; at higher loads, damage is more severe in the inert atmosphere. For a highly-refined mineral oil, better performance is shown in an inert atmosphere than in either a room-air or wet-air atmosphere. Based on microscopic examination of damaged gears and surface finish measurements, it is concluded that tooth damage in air is due to corrosive wear while in inert atmosphere, scuffing occurs. Both corrosive wear and scuffing can be controlled by additive treatment. A mechanism is discussed which suggests that continued oxide formation from corrosive wear serves to prevent scuffing under high loads.

Influence of environment and grinding on the crystallisation mechanism of ZrO 2 gel

The influence of grinding and surrounding atmosphere on the thermal transformations of zirconia gel has been studied. The XRD analysis of the products obtained by thermal decomposition of zirconia gel has shown that pure tetragonal phase is obtained if the gel decomposition is carried out under high vacuum or dry inert atmosphere, while monoclinic zirconia results from the decomposition of the zirconia gel under air or inert gas saturated with water vapour. A mechanism for the thermal crystallisation of zirconia gel has been proposed from the study of the variation of the crystal size of the monoclinic and tetragonal zirconia phases formed as a function of the temperature and the surrounding atmosphere. The thermal decomposition of ground zirconia leads to the formation of ZrO 2 with a percentage of tetragonal phase closed to 90% irrespectively of the surrounding atmosphere. The stabilisation of the tetragonal phase by grinding seems to be connected with the formation of tetragonal zirconia nuclei that cannot be observed by XRD. The crystallisation enthalpy measurements carried out by DSC support this conclusion.

One-pot synthesis of furocoumarins through cascade addition–cyclization–oxidation

A novel one-pot cascade addition-cyclization-oxidation for the regioselective synthesis of furo[3,2-c]coumarins has been developed; the reaction is mild and easily handled without the necessity for dry solvents and inert atmosphere.

Thermal stability of LiPF 6 salt and Li-ion battery electrolytes containing LiPF 6

The thermal stability of the neat lithium hexafluorophosphate (LiPF 6) salt and of 1 molal (m) solutions of LiPF 6 in prototypical Li-ion battery solvents was studied with thermogravimetric analysis (TGA) and on-line Fourier transform infrared (FTIR). Pure LiPF 6 salt is thermally stable up to 107 °C in a dry inert atmosphere, and its decomposition path is a simple dissociation producing lithium fluoride (LiF) as solid and PF 5 as gaseous products. In the presence of water (300 ppm) in the carrier gas, its decomposition onset temperature is lowered as a result of direct thermal reaction between LiPF 6 and water vapor to form phosphorous oxyfluoride (POF 3) and hydrofluoric acid (HF). No new products were observed in 1 m solutions of LiPF 6 in ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) by on-line TGA–FTIR analysis. The storage of the same solutions in sealed containers at 85 °C for 300–420 h did not produce any significant quantity of new products as well. In particular, no alkylflurophosphates were found in the solutions after storage at elevated temperature. In the absence of either an impurity like alcohol or cathode active material that may (or may not) act as a catalyst, there is no evidence of thermally induced reaction between LiPF 6 and the prototypical Li-ion battery solvents EC, PC, DMC or EMC.

Patterned Conductive Polyaniline on Si(100) Surface via Self-Assembly and Graft Polymerization

A combination of surface graft polymerization of aniline and photopatterned self-assembly monolayer (SAM) was used to generate a well-defined pattern of conductive polyaniline on a Si(100) surface. A self-assembly of phenylsilane monolayer was first generated by reacting a hydroxylated silicon surface with phenyltrichlorosilane under a dry inert (N2) atmosphere. The formed SAM layer has been photopatterned under an UV laser at 263 nm through a lithographic mask. The patterned SAM was reacted with triflic acid (HOTf) under a dry inert atmosphere to remove the benzene rings from the SAM layer. The OTf groups of the triflated SAM have been substituted with aniline under a dry inert atmosphere to generate an aniline-primed substrate which was further used for the graft polymerization of aniline to prepare a patterned conductive polyaniline (PANI) layer. The composition, microstructure, and morphology of PANI grafted silicon surfaces were examined by X-ray photoelectron spectroscopy (XPS), atomic force microsc...

Deformation behaviour of nanocrystalline magnesium

The deformation behaviour of nanocrystalline magnesium was studied. Nanocrystalline magnesium powder was prepared by high energy ball milling in a dry inert gas atmosphere and vacuum cold pressed to form fully dense cylindrical specimens. Compression tests were carded out at room temperature. The samples exhibited remarkably high values of ductility, and a significant improvement in yield strength in sintered specimens. Large yield drops were observed on the stress-strain curve of sintered specimens. The strain rate sensitivity of the flow stress was also measured and compared to the values for commercially available pure magnesium bars. The values of activation volume as well as the stress exponent were found to be significantly lower in the nanocrystalline samples. It is speculated that grain boundary sliding controls the deformation mechanism in the nanocrystalline magnesium samples.

Polymeric anodes for organic light-emitting diodes

Polymer light-emitting diodes based on PPV, for example MEH-PPV, are known to be susceptible to photo-oxidative degradation. The formation of the carbonyl species in the polymer results in quenching of the luminescence. In addition the oxidation process reduces the conjugation of the polymer, leading to lower charge carrier mobilities and consequently higher operating voltages. Previous in situ FTIR studies revealed that even in a dry inert atmosphere polymer oxidation occurs, and that ITO can act as the source of oxygen. In order to explore further the nature of the oxidation mechanism and to provide guidance for its elimination, we have studied the behavior of MEH-PPV LEDs prepared with conducting polymer anodes. When a layer of polyaniline is present between the ITO and the MEH-PPV the device characteristics improve dramatically: the injection voltage drops, the luminous efficiency increases and, most significantly, the rate of decay of the luminance decreases by up to two orders of magnitude. These data not only confirm that ITO is a source of oxygen, but also imply that the oxidation mechanism is due to direct interfacial reaction. We compare several different forms of polyaniline, with different dopants, as well as a derivative of a polythiophene.

Degradation and failure of MEH-PPV light-emitting diodes

Light-emitting diodes made with poly(2-methoxy-5(2′-ethyl)hexoxy-phenylenevinylene) (MEH- PPV) using indium-tin-oxide (ITO) as anode and Ca as cathode have been examined as they age during operation in a dry inert atmosphere. Two primary modes of degradation are identified. First, oxidation of the polymer leads to the formation of aromatic aldehyde, i.e., carbonyl which quenches the fluorescence. The concomitant chain scission results in reduced carrier mobility. ITO is identified as a likely source of oxygen. The second process involves the formation of localized electrical shorts which do not necessarily cause immediate complete failure because they can be isolated by self-induced melting of the surrounding cathode metal. We have not identified the origin of the shorts, but once they are initiated, thermal runaway appears to accelerate their development. The ultimate failure of many MEH-PPV devices occurs when the regions of damaged cathode start to coalesce.

The morphological evolution of hollow shells during the mechanical milling of ductile metals

Mechanical alloying is a ball milling process during which powder particles are repeatedly fractured and welded to produce a homogeneous powder. If a ductile metal or alloy is milled at room temperature in a dry inert atmosphere, welding will predominate over fracture and the particle size will steadily increase with milling time. To inhibit welding and produce a fine powder, it is generally necessary to cool the vial or use process control agents (typically liquid or powdered organic compounds). Since large sized powders are less amenable to subsequent processing techniques, few investigations have been made into the morphology of ductile metals milled for extensive times without temperature control or a process control agent. In this paper the authors report on the morphological evolution of large hollow spheres which are formed when copper (a typical ductile metal) is milled without a process control agent. Milling under these conditions also produces secondary effects such as the formation of smaller spherical shells inside the primary spheres (the so-called Russian Doll effect), but these will not be discussed here. This work is part of a wide study on the morphological development of powders during mechanical alloying, part of which has been reported previously.

Paramagnetic point defects in SnO2and their reactivity with the surrounding gases. Part 1.—Interaction of oxygen lattice centres with vapour-phase H2O, air, inert and combustible gases, as revealed by electron paramagnetic resonance spectroscopy

The formation of oxygen vacancies in powdered SnO2 has been investigated by electron paramagnetic resonance (EPR) spectroscopy. It is suggested that strong resonances at g= 1.89 are responsible for the paramagnetic singly ionized form of the V0 neutral vacancies. These defects were formed under dry inert atmosphere at temperatures above 673 K, while both under inert wet gas or wet air they become stable at lower temperature (473 K). The maximum amounts of V0 were observed under dry H2(0.5%)–air and moist CO (0.5%)–air mixed gases, again at 473 K.A rationale is given for the role of the vapour-phase H2O in promoting the formation of donor centres and in improving the conductance of SnO2 at relatively low temperatures.

Investigation of poly-(p-phenylene) obtained in electrochemical oxidation of benzene in the BuPyClAlCl 3 melt and in organic solvents with oleum

Poly-(p-phenylene) has been obtained in electrochemical oxidation of benzene in the BuPyClAlCl 3 melt. The conductivity of the fresh film is 10–100 S/cm. Even when the film is stored in the dry inert atmosphere, its conductivity reduces. Poly-(p-phenylene) has been also obtained in electrooxidation of benzene with oleum or P 2O 5. Electrochemical properties and IR and ESR spectra have been investigated. The SEM data on the film morphology have been also discussed.

Investigation of Poly-(p-Phenylene) Obtained in Electrochemical Oxidation of Benzene in the BuPyCl-AlCl<sub>3</sub> Melt

Poly(p-phenylene) has been obtained by electrochemic al oxidation of benzene in a BuPyCl-AlCl3 melt. The conductivity of the fresh film is 10 100 S/cm. Even when the film is stored in a dry inert atmosphere, its conductivity is reduced. Electrochemical properties and IR and ESR spectra have been investigated. The polymer has an average chain length of 29 - 30 units.

Investigation of poly( p-phenylene) obtained by electrochemical oxidation of benzene in a BuPyClAlCl 3 melt

Poly( p-phenylene) has been obtained by electrochemical oxidation of benzene in a BuPyClAlCl 3 melt. The conductivity of the fresh film is 10 – 100 S/cm. Even when the film is stored in a dry inert atmosphere, its conductivity is reduced. Electrochemical properties and IR and ESR spectra have been investigated. The polymer has an average chain length of 29 – 30 units.

Synthesis and identification of [ 76As]arsenic trichloride

Radiosynthesis of arsenic trichloride (AsCl 3) was achieved using 76As as the radionuclide of choice for preliminary investigations. The synthesis required neutron activation of arsenic trioxide (As 2O 3) followed by reaction with sulfur monochloride (S 2Cl 2) under a dry inert atmosphere. The synthesized 76AsCl 3 was purified by distillation or partially purified by treatment with dry acetonitrile followed by filtration. Identification was accomplished by thin layer chromatography (TLC) and reversed phase high performance liquid chromatography (HPLC). 76AsCl 3 was used for synthesis of a dihydrophenarsazine derivative.