Study of the Effect of Electron Cooling: Overview of the Current State

Technical Physics - Investigation results of the effect of electron cooling are considered. The current state-of-the-art is analyzed. The possibilities are discussed for the experimental study of...     

Reaction of chloromethyl derivatives of ethyl 3-(furyl)-3-(diethoxyphosphoryl)acrylates with sodium azide and potassium thiocyanate

Reaction of chloromethyl derivatives of ethyl 3-furyl-3(diethoxyphosphoryl)acrylates with sodium azide in acetonitrile in the presence of catalytic amount of potassium iodide proceeds with substitution of halogen with the azido group. The same chloromethyl derivatives react with potassium thiocyanate under analogous conditions to give a mixture of thiocyanates and isothiocyanates in (0.6–0.8) : 1 ratio save the case of ethyl 3-(3-chloromethylfur-2-yl)- and 3-(4-chloromethylfur-3-yl)acrylates when only thiocyanates are formed. Bromination of diethyl 5-methyl-2-furoyl phosphonate with N-bromosuccinimide afforded 5-bromomethyl-2-furoyl phosphonate. In the reaction with potassium thiocyanate it forms only thiocyanate.     

Equilibrium composition and the effective adiabatic exponent of a clustering carbon plasma

The equilibrium composition and the effective adiabatic exponent of a low-temperature carbon plasma containing eight components (C, C₂, C₃, C₄, C₅, C⁺, C₂⁺, and e) are calculated. The temperature and pressure ranges are found in which polyatomic clusters form in a gas flow. It is shown that the effective adiabatic exponent of the carbon plasma is a nonmonotonic function of temperature. In the parameter range where the plasma consists largely of polyatomic clusters, the adiabatic exponent is close to unity. It is noted that anomalously low values of the effective adiabatic exponent indicate a considerable concentration of polyatomic molecules in the plasma jet. Such values can be observed in experiments with a low-temperature carbon plasma flowing about bodies.     

Synthesis of actinomycin analogs: XXIV. Non-symmetric derivatives of actinocin containing benzo-18-crown-6 moiety and tertiary ammonium group

Non-symmetric derivatives of actinocin containing fragments of benzo-18-crown-6 and dimethylaminopropylamine (with the crown ether group separated from the heterocyclic chromophore by β-alanine moiety) have been prepared as models of actinomycin D.     

Kinetic study of bleaching of photoinduced forms of o-methylnitrobenzothiazoles

Photochromic properties of benzothiazole derivatives containing nitro and methyl groups in the ortho positions with respect to each other were studied by flash photolysis. The rate constant of bleaching of the corresponding photoinduced nitronic acids and their anions increases as the CH₃C-CNO₂ bond becomes longer. The application of the thermodynamic approach to predict the kinetic stability of nitronic acids is limited owing to specific intramolecular interactions. The lifetime of photoinduced nitronic acid anions tends to increase with rise in the chemical shift of the methyl protons.     

Generation of a gas-discharge air plasma in a supersonic magnetohydrodynamic channel

A method for ionizing a supersonic air flow is developed to obtain a flow conductivity sufficient for a magnetohydrodynamic (MHD) interaction and generation of a magnetically induced current in a supersonic nozzle. The efficiencies of several (high-frequency, multiple-pulse high-voltage, and combined) methods for initiating a gas discharge used for ionizing air are compared. The supersonic air flow is ionized by a pulse-periodic high-voltage discharge producing an air plasma with a conductivity of up to 20 S/m. The experimentally obtained magnetically induced current of 0.1 A is smaller than the rated value owing to the Hall effect and the electrode voltage drop. The theoretical possibility of obtaining a magnetically induced current in a supersonic air flow is demonstrated; such currents can subsequently be used for controlling the flow in air inlets of aircraft.     

Supersonic flow of a nonequilibrium gas-discharge plasma around a body

The flow of a nonequilibrium gas-discharge plasma around a semicylindrical body is studied. The aim of the study is to see how a change in the degree of nonequilibrium of the incoming plasma changes the separation distance between a shock wave and the body. Experiments are carried out with a supersonic nozzle into which a semicylindrical body is placed. The inlet of the nozzle is connected to a shock tube. In the course of the experiment, electrodes built into the wall of the nozzle initiate a gas discharge in front of the body to produce an additional nonequilibrium ionization in the stationary incoming supersonic flow. The discharge parameters are selected such that the discharge raises the electron temperature and still minimizes heating of the gas. The degree of nonequilibrium of the flow varies with gas-discharge current. Diagnostics of the flow is carried out with a schlieren system based on a semiconductor laser. The system can record flow patterns at definite time instants after discharge initiation.     

Synthesis and Transformations of 5-Substituted 2-Furoyl Phosphonates

5-Chloromethyl-2-furoyl chloride when treated with triethyl phosphite has given 5-chloromethyl-2-furoyl phosphonate. This compound has reacted with sodium azide in the presence of potassium iodide to give 5-azidomethyl-2-furoyl phosphonate. Treatment of 5-chloromethyl-2-furoyl phosphonate with secondary amines even under mild conditions has caused cleavage of P–C bond with liberation of diethyl hydrogen phosphite and formation of 5-chloromethyl-2-furancarboxamide. Butanthiol in the presence of potassium carbonate in acetonitrile has converted the chloromethyl group into the butylthiomethyl one and simultaneously split the P–C bond with the formation of the corresponding thioester. Under the action of S-methylthiuronium iodide and triethylamine, 5-chloromethyl-2-furoyl phosphonate has been unexpectedly reduced into the 5-methyl derivative. 5-Butylthiomethyl- and 4-(N-morpholinomethyl)-2-furoul chlorides have been phosphorylated with triethyl phosphite into the corresponding 5-functionalized 2-furoyl phosphonates. The prepared furoyl phosphonates have reacted with resonance-stabilized phosphoranes to give phosphorylated derivatives of 3-(furyl)acrylates and 4-(furyl)but-3-en-2-one with trans-location of phosphoryl and carbonyl groups with respect to the double bond.

     

Synthesis of ethyl 4-(1,2,3-thiadiazol-4-yl)-5-(bromomethyl)furan-2-carboxylate and its reactions with nucleophiles

By cyclization of carboethoxyhydrazone of ethyl 4-acetyl-5-methylfuran-2-carboxylate under the conditions of Hurd–Mori reaction ethyl 4-(1,2,3-thiadiazol-4-yl)-5-methylfuran-2-carboxylate was synthesized. The ester obtained was brominated with N-bromosuccinimide at the methyl group in the furan ring. This bromide reacts with various N-, S-, O-, and P-nucleophiles to form the corresponding substitution products. Furylthiadiazole fragment remains stable in the course of these transformations.