A facile synthesis of alkyl substituted maleic anhydrides: radical approach

Synthetic background for the preparation of alkyl substituted maleic anhydrides and maleimides based on radical alkylation of 2,3-dichloromaleic anhydride (maleimide) by hydrocarbons was developed. The best conditions for the selective synthesis of 2-alkyl-3-chloro- and unsymmetrically substituted dialkylmaleic anhydrides were elaborated.     

Cathodoluminescence of Ge, Si, and O implanted SiO2 layers and the role of mobile oxygen in defect transformations

Thermally grown SiO₂ layers of thickness d=500 nm have been implanted by Ge⁺, Si⁺, and O⁺ ions of energy 350, 150, and 100 keV, respectively, and a uniform implantation dose of D_i=5×10¹⁶ ions/cm². Thus the implantation profiles are expected with a concentration maximum of nearly 4 at.% at the half-depth d_m≅250 nm of the SiO₂ layers. After thermal annealing to 900 °C for 1 h in dry nitrogen or vacuum the typical violet luminescence band (λ=400 nm) of the Ge⁺ implanted centers is increased more than 200-fold and the Ge luminescent center depth profile is shifted from about 250 to 170 nm towards the surface as determined by cathodoluminescence (CL) depth profiling. Implanting oxygen increases the red band (λ=650 nm) but does not affect the blue band (λ=460 nm). Silicon surplus increases the amplitude of the blue (B) luminescence, but reduces the amplitude of the red (R) one. Studying the irradiation dose dependence of these blue and red bands we have established defect kinetics in SiO₂ including six main defects and precursors, including the non-bridging oxygen hole center for the red luminescence, the twofold-coordinated silicon as the oxygen deficient center ODC(2) for the blue luminescence and the mobile oxygen as the main transmitter between precursors and the radiation induced defects. The kinetics are described by a set of eight differential equations which predict the dose dependence of the CL.     

Observation of a new photoluminescence band at 320 nm under 270 nm excitation in Ge-doped silica glass

We investigate the influence of temperature on photoluminescence (PL) in Ge-doped silica glass. Under 270 nm excitation, we observe only one PL band at 424 nm at room temperature (RT). This band shifts to 436 nm with cooling (4 K), and a new PL band is recorded at 320 nm. We assign these PL bands to triplet-to-singlet and singlet-to-singlet transitions of a same Ge-related defect, whose structure is still unknown. The shift of the PL band (from 424 nm at RT to 436 nm at 4 K) is explained by the decrease of the overlap between PLs from different centers.     

Positron annihilation spectroscopy in studying the basicity of a series of <Emphasis Type="Italic">n</Emphasis>-alcohols

A series of alcohols is studied by means of positron annihilation lifetime spectroscopy. The fourth lifetime component of the τ₄ positronium is determined.     

Magnetism of crustal rocks: Implications for the Earth’s evolution

New approaches to the study of the geomagnetic field history, rock magnetism, and the global features of rock magnetism are discussed in relation to the Earth’s evolution. A method for solving the problem of the existence of reversals by investigating the phenomenon of self-reversal in rocks is proposed.     

Ion neutralization model of galvanic cell operation

An ion neutralization model of galvanic cell operation is developed. The electromotive force in this model is formed at the electrode interface owing to the different energies of conduction electrons bonds in electrodes. Constant continuous current is ensured by neutralization of electrolyte ions on the electrode surface. Charge capacity is determined by electrolyte volume and the rate of electrochemical degradation of electrode surfaces in the electrolyte. Potential energy of electrolyte ions serve as the energy source.     

Magnetization self-reversal in natural ferrite

Self-reversal of thermal magnetization in natural ferrite (a solid solution of the magnetite and maghemite with Curie temperature of 595°C) was studied. The experimental results show that self-reversal occurs as a result of the effect of negative exchange anisotropy in the vicinity of the Curie temperature via a mechanism related to the presence of a weak magnetic sublattice in ferrite.     

Reactions of α-nitroacrylates with thiophenols

Reactions of α-nitroacrylates with aromatic thiols like 4-methyl- and 4-chlorothiophenols afford a series of new 3-arylsulfanyl-2-nitropropanoates. The latter were isolated as diastereomerically pure substances or mixtures of two diastereomers. Structures of the obtained S-adducts were confirmed by IR, ¹H and ¹³C-{¹H} NMR spectroscopy using HMQC and HMBC experiments.     

Structure of 3,4-dinitro-3,4-dimethyl-1,1-diphenyl-1-silacyclopentane

Conclusions 3,4-Dinitro-3,4-dimethyl-1,1-diphenyl-1-silacyclopentane in the liquid phase has a half-chair conformation, and in the solid phase, its conformation is described by a form intermediate between the half-chair and the envelope conformation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2731–2736, December, 1985.