The disorder-longitudinal acoustic mode of oligo (ethylene glycol)-lithium trifluoromethane sulfonate solutions as studied by FT Raman spectroscopy

This work presents the results of Fourier transform Raman spectroscopy investigations of the disorder-longitudinal acoustic mode (D-LAM) of oligo(ethylene glycol) dimethyl ether-lithium trifluoromethane sulfonate solutions in dependence on oligomer chain length, temperature and salt concentration. The peak position and the bandwidth of this mode depend on the long-range conformational disorder of oligo(ethylene glycol) chains. The addition of salt causes a marked increase of the long-range conformational disorder. The frequency shift of the D-LAM combined with changes in the asymmetric CH₂ stretching bands indicate that the increasing long-range conformational disorder is connected with an increasing short-range conformational disorder of oligomer chains in a linear relationship.     

Trimethylsilyl and diethylboron derivatives of ethyl N-nitrocarbamate

Conclusions The trimethylsilyl and diethylboron derivatives of ethyl-N-nitrocarbamate were prepared.The former compound was found to exist as an equilibrium mixture of three stereoisomers, i.e., the N- and O-derivatives together with the previously unknown imide isomer. A mechanism of the tautomeric rearrangements in the system, involving both the charged ring intramolecular and the dissociative migration of the Si(CH₃)₃ group is suggested.The latter compound appears to exist in its imide form in which the boron atom is coordinated to the carbonyl group oxygen. The pyridine complex of this derivative has the N-isomer structure.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2547–2557, November, 1976.We are grateful to N. O. Cherskaya for recording the low-temperature IR spectra of (I) and to N. I. Shlykova and O. A. Luk'yanov for their help in preparing (V).     

Nitro derivatives of the thiophene series. 3. Study of the nitration of thiophene α,β-unsaturated ketones in the presence of protic and aprotic acids

The nitration of 4-(5-R-2-thienyl) but-3-en-2-ones (R = H, CH₃, C₂H₅) with a nitrating mixture and group I and III metal nitrates in concentrated sulfuric and trifluoroacetic acids, as well as in the presence of aluminum chloride, was investigated. Nitration with a nitrating mixture and potassium, sodium, lithium, copper, and aluminum nitrates in sulfuric acid takes place in the heterocyclic ring to give a mixture of nitro ketones. Nitration in trifluoroacetic acid and in the presence of aluminum chloride proceeds with the formation of a single -nitro ketone. The structures of the substances obtained were proved by means of the IR and PMR spectra. A possible mechanism of the reaction is discussed.See [1] for Communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 753–757, June, 1981.     

Heterocyclic Quinones in the Nenitzescu Reaction. Synthesis of Furo- and Pyrrolobenzothiazoles from 2-Methyl-4,7-dioxobenzothiazole

Treatment of the enamines of acetylacetone and benzoylacetone with 2-methyl-4,7-dioxobenzothiazole under Nenitzescu reaction conditions gave furo[2,3-e]benzothiazoles (in acetic acid) and pyrrolo[2,3-e]benzothiazoles (in nitromethane). Using enamines of acetoacetic ester gave exclusively pyrrolo[2,3-e]benzothiazoles.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 252–258, February, 2005.     

Electrophilic cyclization of α-series monoterpene ω-derivatives

New information is discussed concerning the protic and Lewis acid-initiated electrophilic cyclization reaction of -monoterpenols and their acetates; the distinguishing feature of these reactions is their termination by isopropenyl residues in these molecules. The reactions have been found to be general in nature, given additional functionalization of the terminator by chloro-, sulfonyl, sulfonylmethyl, or ester substituents. Cyclization of these linear substrates has also been shown to provide a convenient method for the synthesis of dimethylvinylcyclohexene derivatives and related cyclohexanediols, which are not readily available by other methods.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1361–1367, June, 1990.     

Temperature-dependent segregation of Pr3+ impurity ions in Y2SiO5:Pr3+ and YPO4:Pr3+ nanocrystals

Stationary and time-resolved spectroscopic methods are used to show that the impurity ions in Y₂SiO₅:Pr³⁺ and YPO₄:Pr³⁺ nanocrystals are distributed nonuniformly. This nonuniform distribution is found to be caused by the temperature-dependent segregation of Pr³⁺ ions near the surface of a nanocrystal. The motion of the activator ions from the bulk of a nanocrystal to the near-surface layer is traced when the activator concentration and the heat-treatment parameters are varied over wide ranges, and the main parameters of this effect (impurity redistribution intensity and time, diffusion coefficient) are estimated.