Effect of Temperature on the Growth Rate of Pre-Explosion Luminescence in Silver Azide

The effect of temperature on the growth rate of pre-explosion luminescence in AgN₃ crystals is examined. It is found in experiments that the reaction rate of the explosive decomposition at 300 K is higher than at 80 K. It can be inferred from here that the limiting stage for the chain reaction is electron capture on a neutral center (divacancy). The data obtained agree well, both qualitatively and quantitatively, with the previously reported model of initiation in heavy metal azides, thus providing support to the divacancy model.__________Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 3, pp. 106–109, May–June, 2005.     

Regioselective Synthesis of β‐Aryl Enaminones and 1,4,5‐ Trisubstituted 1,2,3‐Triazoles from Chalcones and Benzyl Azides

A highly regioselective synthesis of β‐aryl enaminones and 1,4,5‐trisubstituted 1,2,3‐triazoles from chalcones and benzyl azides based on reaction solvent selection is reported. In the presence of a catalytic amount of Ce(OTf)₃, reactions of chalcones with benzyl azides in DMF at 100 °C afforded densely substituted Z‐β‐aryl enaminones in good to excellent yields, whereas treatment of chalcones with benzyl azides in toluene at 100 °C selectively produced 1,4,5‐trisubstituted 1,2,3‐triazoles in excellent yields.

     

Diazotization–azidation of amines in water by using crosslinked poly(4‐vinylpyridine)‐supported azide ion

The use of polymeric reagents simplifies routine azidation of diazonium salts, because it eliminates the traditional purification. An efficient, simple, and effective method for the preparation of aryl azides is described. The synthesis of aromatic azides from the corresponding amines is accomplished under mild conditions with sodium nitrite in the presence of p‐toluenesulfonic acid or concentrated H₂SO₄ at low temperature (0–5°C to room temperature). The obtained relatively stable diazonium salts, followed by treatment with a polymer‐supported azide ion in water at room temperature to produce the corresponding aryl azides. The spent polymeric reagents can be regenerated and reused for several times without losing their activity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

对硝基叠氮苄的合成

有机叠氮化合物在合成反应中有着重要意义。对硝基溴化苄和叠氮化钠在一定条件下反应，得到对硝基叠氮苄。     

Catalytic azide reduction in biological environments

In the quest for the identification of catalytic transformations to be used in chemical biology and medicinal chemistry, we identified iron(III) meso-tetraarylporphines as efficient catalysts for the reduction of aromatic azides to their amines. The reaction uses thiols as reducing agents and tolerates water, air, and other biological components. A caged fluorophore was employed to demonstrate that the reduction can be performed even in living mammalian cells. However, in vivo experiments in nematodes (Caenorhabditis elegans) and zebrafish (Danio rerio) revealed a limitation to this method: the metabolic reduction of aromatic azides.     

Polymer-grafted multi-walled carbon nanotubes through surface-initiated ring-opening polymerization and click reaction

Multi-walled carbon nanotubes (MWNTs) are modified to possess the hydroxyl groups and are used as coinitiators to polymerize poly(ε-caprolactone) (PCL) or poly(α-chloro-ε-caprolactone) (PαClCL) by surface-initiated ring-opening polymerization. Pendent chlorides were converted into azides by the reaction with sodium azides. Finally, various types of terminal alkynes were reacted with pendent azides by copper-catalyzed Huisgen’s 1,3-dipolar cycloaddition (click reaction). Chemical structure of resulting product and the quantities of grafted polymer were determined by Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS). High-resolution transmission electron microscopy (HR-TEM) images clearly indicate that the nanotubes were coated with a polymer layer. The MWNT-g-PCLs and MWNT-g-(PαN₃CL-g-alkyne)s are well dispersed in the organic solvent. The dispersability of MWNTs with grafted organic moieties is easier in CHCl₃ than in THF. The average thickness of the enwrapped polymer layer is approximately 8-10 nm for MWNT-g-PCL and 3 nm for MWNT-g-(PαN₃CL-g-PBA).     

Novel Palladium‐on‐Carbon/Diphenyl Sulfide Complex for Chemoselective Hydrogenation: Preparation,Characterization, and Application

A diphenyl sulfide immobilized on palladium‐on‐carbon system, Pd/C[Ph₂S], was developed to achieve the highly chemoselective hydrogenation of alkenes, acetylenes, azides, and nitro groups in the presence of aromatic ketones, halides, benzyl esters, and N‐Cbz protective groups. Instrumental analyses of the heterogeneous catalyst demonstrated that diphenyl sulfide was embedded on Pd/C via coordination of its sulfur atom to palladium metal or physical interaction with graphite layers of the activated carbon. The catalyst could be recovered and reused at least five times without any significant loss of the reactivity.     

Synthesis of poly(methyl methacrylate‐g‐glycidyl azide) graft copolymers using N,N‐dithiocarbamate‐mediated iniferters

A glycidyl azide polymer with pendent N, N‐diethyl dithiocarbamate groups (GAP‐DDC) was prepared by the reaction of poly(epichlorohydrin) (PECH) with pendent N, N‐diethyl dithiocarbamate groups (PECH‐DDC) and sodium azide (NaN₃) in dimethylformamide (DMF). It was then used as a macro‐photoinitiator for the graft polymerization of methyl methacrylate (MMA). Photopolymerization was carried out in a photochemical reactor at a wavelength greater than 300 nm. Conversion was determined gravimetrically and first‐order time conversion plot for the polymerization system showed linear increase with the polymerization time indicating that polymerization proceed in controlled fashion. The molecular weight distribution (M_w/M_n) was in the range of 1.4–1.6 during polymerization. The formation of poly(methyl methacrylate‐g‐glycidyl azide) (PMMA‐g‐GAP) graft copolymer was characterized by gel permeation chromatography, FT‐IR spectroscopy, Thermogravimetric analysis, and differential scanning calorimetry. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Production of nitride and carbonitride powders from inorganic azides by self-propagating high-temperature synthesis

The paper sums up studies into the production of nitride and carbonitride powders from inorganic azides by self-propagating high-temperature synthesis. Due to the high purity of such powders and the anisotropic or branched structure of their particles, it was possible to make a pore-free ceramic material withK _lc=8–12 MPa·m^1/2 without sintering activators.     

Preparation and characterization of polystyrene modified single‐walled carbon nanotube

A halogen atom terminated Polystyrene (PSt) was prepared by means of atom transfer radical polymerization. Then, the halogen atom was converted into ‐N₃ group and a ‐N₃ terminated PSt was obtained. Finally PSt was grafted onto the surface of single walled carbon nanotube (SWNT) by the reaction of azide group with SWNT. Comparison of X‐ray photoelectron spectrometer of N1s electron belonging to ‐N₃ and the surface of SWNT demonstrated that three‐membered rings were formed by releasing N₂ from ‐N₃ during the reaction. The structure of PSt modified SWNT was characterized by FTIR, UV, Raman spectrum, and TEM. The experimental results showed that the PSt was connected assuredly to SWNT by the covalent bond. TGA data showed that the amount of PSt on the surface of SWNT firstly increased with growing of PSt and then decrease when continues to grow. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Correlation of Structure and Sensitivity in Inorganic Azides II. Effect of Lattice Defects on Non Bonded Nitrogen to Nitrogen Distances

The sensitivity of explosives during handling operation is an important subject for explosives safety. Current ability to predict sensitivity is based on a series of empirical rules for different classes of explosive compounds based on their chemical composition. Whilst these may be valid for organic classes, inorganic materials do not conform to any of these patterns. There was a very good correlation found between impact sensitivity and the minimum non bonded nitrogen to nitrogen distance across a wide variety of azides. This correlation suggests reduction in the atomic movements required to produce the reaction products. This study examines the structure of a number of inorganic azides containing defects using molecular mechanics based on a Universal Force Field (UFF) approach, previously validated for a range of perfect lattices, with RMS deviations of between 7 and 11 pm from the original crystal structure following operation of the minimisation technique from a disordered arrangement. Using the UFF method, appropriate point defects (Schottky and Frenkel pairs) were modelled for these azides under conditions of maximum and minimum achievable pair separation. The maximum limit on pair separation was a result of the explicit modelling being limited to a 3×3×3 unit cell matrix. The results showed that the minimum non bond nitrogen to nitrogen distance narrowed in the presence of defects for all azides. In two cases, RbN₃ and TlN_3, this reduction in non bonded nitrogen to nitrogen distances was dramatically different from the other azides and was very dependant on the defect configuration and separation. This may indicate that the sensitivity of these two azides containing defects, is greater than the ideal crystal structure would suggest. If the normal production of this azide produces a significantly defective structure then it may well explain the enhanced sensitivity.     

Thermal characterization of glycidyl azide polymer (GAP) and GAP‐based binders for composite propellants

Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) were used to investigate the thermal behavior of glycidyl azide polymer (GAP) and GAP‐based binders, which are of potential interest for the development of high‐performance energetic propellants. The glass transition temperature (T_g) and decomposition temperature (T_d) of pure GAP were found to be −45 and 242°C, respectively. The energy released during decomposition (ΔH_d) was measured as 485 cal/g. The effect of the heating rate on these properties was also investigated. Then, to decrease its T_g, GAP was mixed with the plasticizers dioctiladipate (DOA) and bis‐2,2‐dinitropropyl acetal formal (BDNPA/F). The thermal characterization results showed that BDNPA/F is a suitable plasticiser for GAP‐based propellants. Later, GAP was crosslinked by using the curing agent triisocyanate N‐100 and a curing catalyst dibuthyltin dilaurate (DBTDL). The thermal characterization showed that crosslinking increases the T_g and decreases the T_d of GAP. The T_g of cured GAP was decreased to sufficiently low temperatures (−45°C) by using BDNPA/F. The decomposition reaction‐rate constants were calculated. It can be concluded that the binder developed by using GAP/N‐100/BDNPA/F/DBTDL may meet the requirements of the properties that makes it useful for future propellant formulations. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 538–546, 2000     

In situ grafting MPEG on the surface of cell-loaded microcapsules for protein repellency

The protein repelled alginate-graft-BAT/chitosan/MPEG-norbornene (A_BCP_N) hydrogel microcapsules were achieved by copper-free click reaction between azides from BAT and alkylenes from norbornene. The MPEG modified polyelectrolyte microcapsules showed significant resistance to immune protein adsorption and good biocompatibility in vivo. Moreover, the mild reaction condition made it feasible that the microcapsules could be formed and modified in situ even when live cells were encapsulated, and precluded the damage cause by other violent modifications methods to transplanted cells or tissues.     

Manganese(II)‐Mediated Domino Annulation Reaction of Vinyl Azides and 4‐Hydroxycoumarin: A Stereoselective Synthesis of Spirobenzofuranone‐lactams

A manganese(II) acetate‐catalyzed domino reaction of vinyl azides and 4‐hydroxycoumarin has been developed for the synthesis of polyfunctionalized spirofuranone‐lactams. A wide range of vinyl azides are capable of providing the desired spirofuranone‐lactams in good to excellent yields. The reaction was achieved via thermal decomposition of vinyl azides to 2H‐azirines, followed by an intramolecular nucleophilic attack and stereoselective cyclization. The mild reaction conditions and easy operation make this reaction advantageous for the synthesis of spirofuranone‐lactams.

     

Reactions of Azides with Electrophiles: New Methods for the Generation of Cationic 2-Azabutadienes. Synthesis of 1,2, 3,4-Tetrahydroquinolines and 1,2-Dihydroquinolines via a Hetero Diels–Alder Reaction

Two methods for the generation of iminium ions of the type ArN⁺(X)=CHR (X = H or alkyl, R = H or alkyl) are reported: (1) the Bronsted-acid-promoted rearrangement of benzylic azides and (2) the intermolecular Schmidt reactions of azides XN₃ (X = aliphatic) with benzylic carbocations derived from benzylic alcohols ArCH(R)OH. The iminium ions ArN⁺(X)=CHR behave as cationic 2-azabutadienes in the presence of alkenes and alkynes, producing 1,2, 3,4-tetrahydroquinolines and 1,2-dihydroquinolines by a hetero Diels–Alder reaction.     

Synthesis and characterization of polyhedral oligomeric azido‐octaphenylsilsesquioxane

Polyhedral oligomeric azido‐octaphenylsilsesquioxane (N₃‐OPS) was synthesized from octaaminophenylsilsesquioxane (OAPS) via its diazonium salt. The synthesis included nitration of octaphenylsilsesquioxane (OPS) to octanitrophenylsilsesquioxane (ONPS), conversion of ONPS into octaaminophenylsilsesquioxane (OAPS), and conversion of OAPS into N₃‐OPS. The kinetics of the conversion of OAPS into N₃‐OPS were studied by recording the volume of N₂ gas released with the reaction time, which revealed it to be a 1st order reaction. The chemical structures of ONPS, OAPS and N₃‐OPS were characterized by ¹H‐NMR, GPC, FTIR, ²⁹Si solid NMR, ¹³C‐NMR, XRD, and elemental analysis. It is proposed that the diazonium salt of OAPS was substituted by the main ? N₃ group and a few of the ? OH groups. The ratio of ? N₃:? OH was calculated to be approximately 68:32 in N₃‐OPS on the basis of the elemental analysis and ¹H‐NMR. XRD suggested that N₃‐OPS was a kind of amorphous compound. The two‐step conversion mechanism of OAPS to N₃‐OPS was briefly discussed. TGA results showed that N₃‐OPS was stable at ambient temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis of Oxazolidin‐2‐ones and Imidazolidin‐2‐ones Directly from 1,3‐Diols or 3‐Amino Alcohols using Iodobenzene Dichloride and Sodium Azide

A general and efficient method for the synthesis of oxazolidin‐2‐ones and imidazolidin‐2‐ones directly from 1,3‐diols and 3‐amino alcohols has been developed using the same reagent combination of iodobenzene dichloride (PhICl₂) and sodium azide (NaN₃).

     

Molecular-beam mass-spectrometric study of the flame structure of composite propellants based on nitramines and glycidyl azide polymer at a pressure of 1 MPa

A study was performed of the chemical and thermal structure of flames of model composite propellants based on cyclic nitramines (RDX and HMX) and an active binder (glycidyl azide polymer) at a pressure of 1 MPa. Propellant burning rates were measured. The chemical structure of the flame was studied using molecular-beam mass spectrometry, which previously has not been employed at high pressures. Eleven species (H₂, H₂O, HCN, N₂, CO, CH₂O, NO, N₂O, CO₂, NO₂, and nitramine vapor) were identified, and their concentration profiles, including the composition near the burning surface were measured. Two chemical-reaction zones were observed. It was shown that flames of nitramine/glycidyl azide polymer propellants are dominated by the same reactions as in flames of pure nitramines. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 6, pp. 48–57, November–December, 2006.     

Lithium perchlorate promoted highly regioselective ring opening of epoxides under solvent-free conditions

A simple and efficient synthesis of diol diesters, protected chlorohydrins, chlorohydrins and β-hydroxy azides with acetyl or benzoyl, TMSN₃ and TMSCl groups has been achieved by ring opening of epoxides with acetic anhydride, acetyl chloride or benzoyl chloride and TMSN₃ using catalytic amount of lithium perchlorate under solvent-free conditions. All reactions proceeded in short times and afforded the corresponding products in good to excellent yields under mild reaction conditions. LiClO₄ shows enhanced reactivity for the ring opening of epoxides under solvent-free conditions, therefore, reducing the reaction times dramatically and improved the yields and amount of catalyst.