Catalytic opening of the diaziridine fragment in 6-aryl-1,5-diazabicyclo[3.1.0]hexanes

Treatment of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes with Lewis acids [BF₃·Et₂O or In(OTf)₃] promotes opening of the diaziridine ring, followed by formation of 1,3-dipolar cycloaddition products with N-arylmaleimides. The conversion of the initial diaziridine depends on the nature of the 6-aryl group. Diazabicyclohexanes with donor substituents react quantitatively to give (in the absence of dipolarophiles) the corresponding azomethine imine dimers, 1,2,4,5-tetrazine derivatives. The conversion of diazabicyclohexanes having acceptor substituents is poor; simultaneously, the fraction of the hydrolysis products increases. The stereoselectivity in the 1,3-dipolar cycloaddition, i.e. the ratio of the cis-and trans-adducts, depends on the catalyst and solvent. Azomethine imine dimers react with N-arylmaleimides in the presence of indium(III) trifluoromethanesulfonate to give the same 1,3-dipolar cycloaddition products as those obtained from parent 1,5-diazabicyclohexanes.     

Influence of electron irradiation on the properties of α-aluminum hydride polymorph

Russian Chemical Bulletin - Changes in dielectric properties and thermal stability of the alpha-aluminum hydride polymorph (α-AlH3) after irradiation with electrons with an energy of 7 MeV...     

A Gorizont neutron reflectometer—small-angle spectrometer based on the IN-06 pulsed neutron source

The Gorizont time-of-flight neutron reflectometer—small-angle spectrometer has been designed, manufactured, and assembled to operate with the IN-0 6 pulsed neutron source. The instrument has a vertical neutron scattering plane enabling research on liquid surfaces and interfaces. Model calculations of neutron spectra, beam profiles, and spectrometer resolutions have been performed via the Monte Carlo method. The spectrometer operates at wavelengths from 1.5 to 9 Å and ensures measurements in the momentum-transfer range of 0.003—1.5 Å^-1.     

The Crystallinity of γ-Irradiated Poly(tetrafluoroethylene)

The influence of absorbed -radiation dose over the range 0–220 kGy on the heat of fusion and the crystallinity of industrial specimens of bulk PTFE and PTFE films were studied using the techniques of adiabatic and differential scanning calorimetry. The thermodynamic characteristics of transitions in the interval 287–310 K in the original and the irradiated polymer were determined. Based on the results obtained, a new crystal modification other than the one present in the unirradiated material was assumed to be formed during -irradiation.     

Prediction of thermal explosion parameters for energetic materials on the basis of thermal analysis data

Results obtained in calculations of thermal ignition delay periods in a wide temperature range are in good agreement with published data for octogene samples in the form of a sphere 12.7 mm in diameter and cylindrical NEPE propellant samples with diameters of 20 to 80 mm. The kinetic parameters of the thermal decomposition of materials, used in the calculations, were obtained by the DSC method with the use of hermetically sealed crucibles and crucibles with perforated covers under a nitrogen pressure of 10 MPa at heating rates of 0.1 to 1.0 deg min^–1.     

Effect of γ-irradiation on the properties of poly(ester urethane) elastomer

The influence of irradiation with ⁶⁰Co γ-rays on gelation, change in the mechanical characteristics, and the formation of supermolecular structure in a poly(ester urethane) elastomer synthesized from oligoether adipate and diisocyanate, as well as a diol with or without double carbon-carbon bonds, was studied. It was found that the presence of double carbon-carbon bonds in the structure of the elastomer ensures the predominance of crosslinking over degradation processes. It was shown that γ-irradiation at a dose of 380 kGy is accompanied by the formation of a microglobular structure of ～1 μm size. The specifics of changes in the mechanical characteristics depending on the absorbed dose are discussed.     

(Z)-1-alkylidene- and 1-arylmethylidene-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ides and their cycloaddition to N-arylmaleimides

The reaction of (Z)-1-arylmethylidene-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ides with para-substituted N-arylmaleimides at 110°C is cis-stereoselective [cis/trans-adduct ratio ??(9?C10): 1]. Under analogous conditions, the conversion of (Z)-1-(2,6-dichlorophenylmethylidene)-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ide in the reaction with N-(4-methoxyphenyl)maleimide in 6-7 h did not exceed 1?C2%. The cycloaddition of (Z)-1-ethylidene- and (Z)-1-(2-methylpropylidene)-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ides to N-arylmaleimides, regardless of the substituent in the phenyl group of the latter, gave preferentially the corresponding trans-adducts, which cannot be rationalized only by steric effect of substituents in terms of the concerted mechanism.