Erratum to: “Determination of Parameters of Phase Element under Conditions of Multiray Interference”

Optics and Spectroscopy -     

Determination of parameters of phase element under conditions of multiray interference

The method of measuring the phase shift Γ and the relative amplitude transmission coefficient F of a phase element is developed and experimentally tested. The conditions minimizing an experimental error of measuring Γ and F are determined. The accuracy of the proposed method is shown to be comparable to that of the currently used one; however, the proposed method is simpler and allows automation.     

Thermal Rearrangements of 3<Emphasis Type="Italic">H</Emphasis>- and 4<Emphasis Type="Italic">H</Emphasis>-Pyrazoles Prepared by Reactions of 9-Diazofluoren with Methyl Tetrolate and Methyl 3-Phenylpropiolate

9-Diazofluoren adds in Et₂O at 20°C to methyltetrolate in keeping with Auwers rule and nonregioselectively adds to methyl-3-phenylpropiolate with the formation of spirocyclic 3H-pyrazoles. The methyltetrolate adduct at boiling in toluene converts into methyl 3a-methyl-3aH-dibenzo[e,g]indazole-3-carboxylate, at 190°C in benzene, into methyl 3-methyl-2H-dibenzo[e,g]indazole-2-carboxylate, and at 160°C in methanol, into 3-methyl-2H-dibenzo[e,g]indazole. Auwers adduct of methyl 3-phenylpropiolate at boiling in benzene gives cyclopropene derivative and at boiling in methanol isomerizes into methyl 3a-phenyl-3aHdibenzo[e,g]indazole-3-carboxylate. Anti-Auwers adduct at boiling in benzene isomerizes into methyl 2-phenylpyrazolo[1,5-f]phenanthridine-3-carboxylate.     

Polyacrylonitrile-based FeCo/C nanocomposites: Preparation and magnetic properties

Metal–carbon nanocomposites that represent FeCo alloy nanoparticles uniformly distributed over the carbon matrix, were prepared by the IR pyrolysis of precursors comprising polyacrylonitrile (PAN), iron acetylacetonate, and cobalt acetate (the metal ratio in the precursors was Fe: Co = 1: 1, 3: 1). The composition of FeCo alloy nanoparticles satisfies the tailored ratio Fe: Co. The FeCo phase is formed at synthesis temperatures in the range 500–600°С; at T ≤ 500°С only FCC-Co-base solid solutions are observed. The nanocomposites prepared at T ≥ 600°С simultaneously contain FeCo intermetallic nanoparticles and an insignificant amount of a FCC-Co phase or a cobalt-base solid solution phase. The saturation magnetization of FeCo/C metal–carbon nanocomposites is determined by the mean nanoparticle size and the alloy composition, and ranges from 36 to 64 (A m²)/kg (when Fe: Co = 1: 1) and from 35 to 52 (A m²)/kg (when Fe: Co = 3: 1) at synthesis temperatures in the range 600–800°С.     

Stereochemical characteristics of the ammonia reaction with perfluoro-2-methyl-2-pentenethiocyanate-3: The defining role of the steric factor determined by geometric modeling

Geometric modeling has been used to analyze the stereochemical characteristics of the ammonia reaction with perfluoro-2-methyl-2-pentenethiocyanate-3. This reaction is stereospecific because it results in only one E stereoisomer of 2-aminoperfluoro-4,4-dimethyl-4,5-dihydro-5-ethylidene-1,3-thiazole (3). It is shown that such stereospecificity is determined by a lower steric hindrance in the anion from which the E isomer is formed as compared to that in the anion from which a Z isomer would be formed. Strong steric hindrances associated with the amino group attached to a double bond exclude the heat-dependent cyclization of E-2,4-diaminoperfluoro-4-methyl-2-pentenethiocyanate-3 (4), which would result in the formation of a thiazole ring. The substitution of the fluorine atom at the double exocyclic bond in thiazoline E-3 by an amino group does not occur because of the electron destabilization of the transition state resulting from the repulsion of the unshared electron pairs of the carbanion and the sulphur atom .A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 343–349, February, 1992.