Monitoring System of High Voltage Dielectric Equipment

Based on the research of the main causes of dielectric elements premature aging and electrical destruction of primary dielectric elements in high voltage electrical equipment the complex method for remote monitoring of said electrical equipment has been developed. The developed mobile diagnostic device is allowing detection and periodic control of the most dangerous defects. The set of diagnostic parameters of defects was experimentally obtained by using three physical methods (electromagnetic, optical, and acoustic), and allows to inspect the origin and development of defects, and to determine residual life of dielectric elements with a sufficient degree of reliability. The researched characteristics of the kinetics of reduction in operating parameters of polymer insulators permitted the development of the detection of accelerated increase in defects under the influence of ultra-large partial discharges.

2-Butyl-2-tert-butyl-5,5-diethylpyrrolidine-1-oxyls: Synthesis and Properties

Nitroxides are broadly used as molecular probes and labels in biophysics, structural biology, and biomedical research. Resistance of a nitroxide group bearing an unpaired electron to chemical reduction with low-molecular-weight antioxidants and enzymatic systems is of critical importance for these applications. The redox properties of nitroxides are known to depend on the ring size (for cyclic nitroxides) and electronic and steric effects of the substituents. Here, two highly strained nitroxides, 5-(tert-butyl)-5-butyl-2,2-diethyl-3-hydroxypyrrolidin-1-oxyl (4) and 2-(tert-butyl)-2-butyl-5,5-diethyl-3,4-bis(hydroxymethyl)pyrrolidin-1-oxyl (5), were prepared via a reaction of the corresponding 2-tert-butyl-1-pyrroline 1-oxides with butyllithium. Thermal stability and kinetics of reduction of the new nitroxides by ascorbic acid were studied. Nitroxide 5 showed the highest resistance to reduction.

Synthesis of 1-azaspiro[4.4]nonan-1-oxyls via intramolecular 1,3-dipolar cycloaddition

Sterically shielded nitroxides of the pyrrolidine series have shown the highest resistance to reduction. Here we report the synthesis of new pyrrolidine nitroxides from 5,5-dialkyl-1-pyrroline N-oxides via the introduction of a pent-4-enyl group to the nitrone carbon followed by an intramolecular 1,3-dipolar cycloaddition reaction and isoxazolidine ring opening. The kinetics of reduction of the new nitroxides with ascorbate were studied and compared to those of previously published (1S,2R,3′S,4′S,5′S,2″R)-dispiro[(2-hydroxymethyl)cyclopentan-1,2′-(3′,4′-di-tert-butoxy)pyrrolidine-5′,1″-(2″-hydroxymethyl)cyclopentane]-1′-oxyl (1).

Synthesis of 1-azaspiro[4.4]nonan-1-oxyls via Intramolecular 1,3-Dipolar Cycloaddition

Sterically shielded nitroxides of pyrrolidine series are known to demonstrate the highest stability to reduction. Here we report on the synthesis of new pyrrolidine nitroxides from 5,5-dialkyl-1-pyrroline N-oxides via the introduction of pent-4-enyl group to nitrone atom followed by intramolecular 1,3-dipolar cycloaddition reaction and isoxazolidine ring opening. Kinetics of reduction of the new nitroxides with ascorbate was studied and compared to that of previously published 1S,2R,3′S,4′S,5′S,2″R-dispiro[(2-hydroxymethyl)-cyclopentan-1,2′-(3′,4′-di-tert-butoxy)pyrrolidine-5′,1″-(2″-hydroxymethyl)cyclopentane]-1′-oxyl (1).