Mass-spectral behavior of 2-azatriptycene and its derivatives

The mass-spectral behavior of 11 aromatic and partially hydrogenated 2-azatriptycenes was investigated. It was established that the principal fragmentation pathway for these compounds is the formation of [M-nH] ⁺ and [M-nH]²⁺ ions (n = 1–6), as well as pseudoretrodiene fragmentation of the heterocyclic ring with the elimination of the atoms in the 2 and 3 positions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1399–1402, October, 1981.     

Mass-spectral behavior of benzothiolactams and isomeric ω-arylalkyl isothiocyanates

The corresponding five benzothiolactams were obtained by cyclization of racemic arylalkyl isothiocyanates in polyphosphoric acid. The fragmentation of all five pairs of isomeric compounds under the influence of electron impact was investigated thoroughly.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp, 1520–1523, November, 1980.     

Mass-spectral behavior of substituted 2-alkylaminobenzoxazoles and 3-methyl-2-alkyliminobenzoxazolines

Schemes that reflect the peculiarities of each of the investigated groups of compounds and make it possible to distinguish the amino and imino forms are given on the basis of a study of the dissociative ionization processes of 18 2-alkyl(dialkyl)-aminobenzoxazoles and six 3-methyl-2-alkyliminobenzoxazolines. A qualitative relationship between the electronic properties of the substituents in the aromatic ring and the formation of the imino forms of the molecular ions in the gas phase was found.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 304–308, March, 1981.     

Mass-spectral behavior and thermal stability of hetaryl analogs of unsymmetrical benzoins

The main path in the mass-spectral dissociation of the hetaryl analogs of unsymmetrical benzoins is β-fragmentation with cleavage of the central C-C bond. Here, the strongest peak in the mass spectra of α-benzoins is the peak of the hydroxymethylhetaryl cation, and in β-benzoins it is the peak of the hetaroyl cation. The thermal α → β isomerization of the hetaryl analogs of benzoin was studied. In the case of indole and pyrrole derivatives the formation of polyheterocyclic systems is observed. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 515–521, April, 2006.     

Mass-spectral investigation of 4-aryloxazoles

4-(p-Substituted)phenyloxazoles containing electron-donor and electron-acceptor substituents were synthesized and subjected to a mass-spectral study. On the basis of calculations of the free energies liberated in a number of metastable transitions, assumptions regarding the structures of some of the fragment ions are expressed.     

Mass-spectral investigation of indolizine derivatives

The dissociative ionization of substituted 3-aroylindolizines proceeds with the successive loss of an aryl residue and CO. Detachment of OH and CHO groups proceeds simultaneously. The stabilities of the indolizines and the similarly constructed indole derivatives are compared.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 509–513, April, 1975.The authors thank A. B. Belikov for participating in the recording of the mass spectra.     

Mass-spectral investigation of some alkyl- and dialkylamino-substituted oxazolino- and thiazolino-sym-triazines

The mass spectra of eight alkyl- and dialkylamino-substituted oxazolino- and thiazolino-sym-triazines were investigated. It is shown that prior to fragmentation with opening of the oxazoline ring, the excited molecular ions of oxazolino-sym-triazines undergo rearrangement to N-vinyl-substituted sym-triazinols, The dissociative ionization of thiazolino-sym-triazines is primarily due to cleavage of the bonds in the thiazoline ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 124–128, January, 1982.     

Mass-spectral study of heterocyclic analogs of 4-dimethylamino- and 4-azidochalcones

The predominant pathway in the mass-spectral fragmentation of 4-dimethylamino- and 4-azidochalcones under the influence of electron impact is cleavage of the aryl-CO and CO-CH bonds and localization of the charge on the fragment with the lower ionization energy. The characteristic chalcone rearrangement with the ejection of a molecule of CO from the molecular ion and subsequent cyclization and aromatization of the stilbene derivative is also observed; in the case of azides this process takes place only after the loss of a molecule of nitrogen by the molecular ion. The differences in the pathways of fragmentation of the hetero analogs make it possible to identify compounds with , , and orientations of the substituent relative to the heteroring nitrogen atom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 660–664, May, 1991.     

Mass-spectral study of esters of keto acids of the indole series

Under the influence of electron impact, esters of saturated keto acids of the indole series undergo the fragmentation typical for 3-acylindoles, whereas esters of unsaturated and aromatic 3-indolyl keto acids have specific mass spectra that reflect the peculiarities of their structure and the mutual orientation of the substituents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 194–199, February, 1976.     

Mass-spectral investigation of pyrrolo[3,2-c]piperidines

The dissociative ionization of derivatives of pyrrolo[3,2-c]piperidines and their deutero analogs was studied. The successive elimination of the substituents in the piperidine ring, which leads to its aromatization, and cleavage of this ring via a retrodiene fragmentation mechanism are the principal pathways of fragmentation of these substances. The principles found make it possible to determine the position and character of the substituents in the piperidine ring of derivatives of pyrrolo[3,2-c]piperidines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 212–215, February, 1988.     

Preparation of copper-indium sulfide thin films by single-source OMCVD: Mass-spectral investigation of decomposition path of the organometallic sources

In order to prepare high-quality CuInS₂ thin films vapor phase decomposition patterns of three copper-indium binuclear complexes, and as candidates for source materials were investigated using EI MS. The complex 1c showed series of intensive peaks due to the fragmentation of M⁺. For 1a, only a fragmentation pattern starting from BuIn(S₂CNBu₂)₂ was detectable. This should suggest that 1a decomposed into BuIn(S₂CNBu₂)₂ and copper sulfide before vaporization. In addition an ambiguous feature could be observed for 1b, viz. two fragmentation paths. Consequently, we judge that 1c is a suitable source complex to prepare CuInS₂ thin films via a single-source OMCVD process. Thus chalcopyrite CuIns₂ thin films were successfully prepared via single-source OMCVD using 1c as a source complex, with T_substrate400°C, T_source80°C, base pressure 0.7 Torr and carrier (nitrogen) flow rate 0.8 L min^?1. Fragmentation of two copper dithiocarbmates, Cu(S₂CNBu₂)₂ and Cu[S₂CN(i-Pr)₂]₂, and two butylindium thiolates, Bu₂InS(i-Pr) and BuIn[S(i-Pr)]₂, as components of 1 is additionally discussed.     

Polarographic behavior and determination of Flumequine

Flumequine was found to be reduced at the dropping mercury electrode in Britton-Robinson buffer containing methanol as a solubilizer, over the pH range 5–10. A well-defined cathodic wave was produced over this entire range. The wave was characterized as being diffusion-controlled, although adsorption phenomena played a limited role in the reduction process. The proposed method was applied to the determination of Flumequine in tablets, and the results were satisfactorily accurate and precise.     

Adsorption behavior and activity of hexokinase

The study on the adsorption of hexokinase (HK) onto silicon wafers was carried out by means of in situ ellipsometry and atomic force microscopy in the liquid. The thickness values of the adsorbed HK layer determined by both techniques were in excellent agreement and evidenced HK monolayer formation. The adsorption of HK onto Si wafers was favored at low ionic strength, indicating that the adsorption is mainly driven by electrostatic forces, since salt screens not only the segment-segment repulsion but also the segment-surface attraction when the salt concentration increases. The enzymatic activity of free HK and of adsorbed HK was measured as a function of time. Free HK in solution lost activity upon storage. Contrarily, adsorbed HK kept its activity level even after 48 h storage at room temperature. This outstanding behavior was attributed to specific orientation of the HK active site to the solution.     

Structure and fluxional behavior of pentamethoxycarbonylcyclopentadiene

Quantum-chemical calculations by the density functional theory method at the B3LYP/6- 311++G** level have shown that the fulvene form of pentamethoxycarbonylcyclopentadiene 1 in the gas phase is more favorable in energy than cyclopentadiene form 2 by ΔE_ZPE = 7.8 kcal/mol. The fluxional behavior of fulvene 1, detected by dynamic NMR can be explained by the mechanism of circular low-barrier 1,9-O,O'-H shifts accompanied by rotations of the hydroxymethoxymethylene substituent about the С=С bond with the activation barrier ΔE_ZPE= 23.5 (gas) and 20.9 (CH₂Cl₂) kcal/mol. This reaction path is 18.6 kcal/mol more favorable in energy than transition of fulvene 1 to cyclopentadiene 2 with subsequent 1,5- sigmatropic hydrogen shifts in the five-membered ring.     

Spectroscopy behavior of diiodofluorescein and tetrabromofluorescein

The luminescence behavior of diiodofluorescein (DIF) and tetrabromofluorescein (TBF) have been investigated including the solid surface room temperature phosphorescence (SS-RTP) and the room temperature fluorescence (RTF). The luminescence intensities of the two compounds are strongest in alkaline solution. RTP lifetime of the two compounds are in the range of 130-140 ms. The RTP and RTF polarization was in the range of 0.01-0.05. The two analytical methods--SS-RTP and RTF, of the two compounds have been established.