Ammonia-sensing properties of acridine immobilized in SiO2 sol-gel films

The spectral and luminescent properties of acridine in SiO₂ films synthesized by the sol-gel method using acid hydrolysis of tetraethoxysilane are studied. It is shown that acridine in films exists in protonated form. Ammonia-gas-sensing properties of films doped with acridine are studied by the fluorescence response (decrease in the intensity) of the protonated form. The possibility of multiple use of a sample without a noticeable decrease in its sensitivity is demonstrated. It is shown that the fluorescence response to a maximal permissible concentration of ammonia in the gas mixture with argon is 6–8%.     

Haloalkynylation of norbornadiene with haloacetylenes activated with a trifluoroacetyl or ethoxalyl group

Reactions of norbornadiene with haloacetylenes activated with a trifluoroacetyl or ethoxalyl group proceed as stereospecific conjugated exo-addition of the alkynyl substituent and the halogen atom to the double bond of norbornadiene.     

1-Bromo-2-trifluoroacetylcyclobutenes as novel building blocks for the construction of trifluoromethyl substituted heterocycles. Part 2: Synthesis of trifluoromethyl substituted thiophenes, condensed with cyclobutene moieties

This paper describes a novel synthetic approach to 2-cyano-3-trifluoromethylthiophenes fused with cyclobutene rings with variable spiro conjunctions. The reaction of substituted 1-bromo-2-trifluoroacetylcyclobutenes with mercaptoacetonitrile results in the substitution of bromine with S-center to afford the corresponding nitriles in high yields, which form the target thiophenes by subsequent treatment of lithium 2,2,6,6-tetramethylpiperidide and acetic anhydride.     

Addition reactions of 1,1,1-trifluoro-4-trimethylstannylbut-3-yn-2-one and 1,1,1-trifluorobut-3-yn-2-one to some tetrahydropyridines. Synthesis of trifluoroacylated polysubstituted tetrahydroazocines

A reaction of tetrahydropyridines, obtained by the Diels-Alder reaction from α,β-unsat-urated N,N-dimethylhydrazones and methyl acrylate, with acetylenes activated with the trifluoroacetyl group has been studied and found to lead to polysubstituted trifluoroacylated tetrahydroazocines. No cyclobutene intermediates have been detected.     

Optimization of tert-Butyl Perbenzoate Purification

Purification of tert-butyl perbenzoate with an Na₂S₂O₅ solution was studied.     

Spectroscopic and laser characteristics of new efficient luminophores for a wide spectral range based on complexes of dipyrrolylmethene derivatives with difluorine borate

We have studied the spectral-luminescent, lasing, photochemical, and endurance characteristics of a series of new efficiently emitting difluorine borate complexes with dipyrrolylmethenes of different structures. Experimental data have been obtained in polar and nonpolar organic solvents and in solid polymer films involving the participation of silicate structures. We have discussed relations of the structure of investigated compounds and formed solvates with their optical characteristics, and have given guidelines on the use of particular compounds as active media of tunable lasers for determining spectral ranges.     

Structural and phase transformations in ferromanganese alloys during deformation under pressure

Using optical metallographic, TEM, Mössbauer spectroscopy, and X-ray analysis the structural and phase transformations in Fe-(3–55) wt % Mn alloys during shear deformation under pressure were investigated. It is established that a large deformation under high pressure causes the formation of a nanocrystalline structure with grain sizes of 40–60 nm. Nanostructure increases the hysteresis of inverse (hcp-fcc) transformation and stabilizes the (hcp) ? phase in alloys containing more than 40 wt % Mn, up to normal conditions. The Fe-3 wt % Mn alloy after shear under pressure treatment became nanostructured, retaining the original bcc phase state.