Reactions of Polyhalopyridines. 16. Synthesis and Reactions of 2,3,5,6-Tetrafluoro-4-perfluoroalkylthiopyridines

Identical reaction products, viz. 2,3,5,6-tetrafluoro-4-perfluoroalkylthiopyridines 3a-c, were obtained on thermal decomposition of Xe(II) bisperfluoroalkylcarboxylates in the presence of mercaptotetrafluoropyridine and bis(2,3,5,6-tetrafluoro-4-pyridyl) disulfide. Compounds 3a-c readily interact with N-, O-, and S-containing nucleophiles, though with the first two types of reactant only with substitution of fluorine atoms in position 2 of the pyridine ring. In the latter case products are obtained both with retention of the perfluoroalkylthio group on interaction with sodium N,N-dimethyldithiocarbamate, and with total fission of that group in the case of alkali metal methanethiolate and toluenethiolate.     

Computer simulation of proton channelling in silicon

The channelling of 3 MeV protons in the 〈110〉 direction of silicon has been simulated using Vineyard model taking into account thermally vibrating nuclei and energy loss due to ion-electron interactions. A beam made up of constant energy particles but with spatial divergence has been simulated for the purpose. The values of the minimum scattering yield and half width of the channelling dip are shown to be depth sensitive and agree well with the measured values. The dependence of yield on the angle of incidence has been found to give information of all three types of channelling. The critical angles for the three types of channelling and wavelength of planar oscillations are consistent with the previous calculations.     

Energy dependence of multiplicity in proton-nucleus collisions and models of multiparticle production

This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioR _em = 〈n _s〉/〈n _ch〉, where 〈n _ch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,R _em = 1·71 implies an effectiveA-dependence ofR _A =A ^0.18,i.e., a very weak dependence. Predictions ofR _em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production.     

Reactions of polyhalogenopyridines. 15. Reaction of isomeric tetrachlorocyanopyridines and pentachloropyridine with potassium isopropyltrithiocarbonate

The reaction of isomeric tetrachlorocyanopyridines and pentachloropyridine with potassium isopropyltrithiocarbonate was investigated. It was found that the structure and composition of the reaction products depend both on the initial polychloropyridines and on the solvent in which the process is carried out. The intramolecular transformations of the isopropyltrithiocarbonate derivatives of tetrachloro-2-cyanopyridine in acetonitrile solution lead to 1,3-dithiolo[4,5-c]pyridines. In other cases heterocyclization was not observed. If the reactions were conducted in ethanol (except with tetrachloro-3-cyanopyridine) thioalkylation of the pyridine ring occurred.For Communication 14, see [1].Chernogolovka Institute of Chemical Physics, Chernogolovka 142432, Russia. M. V. Lomonosov Moscow State University, Moscow 119899. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 330–341, March, 1998.     

Determination of aromatic hydrocarbons in petroleum jet fuels by capillary gas chromatography and high-performance liquid chromatography

About a hundred hydrocarbon compounds have been identified as components of petroleum jet fuel by capillary gas chromatography and high-performance liquid chromatography. In gas chromatography stuides, glass capillary columns over 100 m long with polysiloxane OV-101 have been used as the stationary phase. In liquid chromatography, 150-mm-long columns with a separation ability of about 60 000 theoretical plates meter of length have been used to separate partitioned fractions of aromatic hydrocarbons from petroleum jet fuels of various origins.     

Thermotropic liquid crystalline polymers. II. Polymers with amino acid fragments in the side chains

The comblike polymers, poly(N^ε-methacryloyl-N^α-acyl) derivatives of L -lysine, which contain amino acid fragments and long sequences of methylene groups in the side chain, were synthesized. This article, which is based on x-ray data, differential thermal analysis, and optical microscopy, describes the structure of these polymers and their properties. It also shows that the combination of anisodiametric side groups with a “rigid” matrix of main chains leads to a liquid crystalline structure of examined polymers.     

Cyclization of N,N-dialkylditiocarbamate and alkylxanthate derivatives of polyhalogenated pyridines in gas and liquid phases

The intramolecular cyclization of 31 polyhalogen substituted pyridines containing N,N-dialkyldithiocarbamate or alkylxanthate groups has been compared in reaction in solution with sodium N,N-dialkyldithiocarbamates or potassium carbetoxydithiolate and in the gas phase under electron ionization (EI). The scheme of fragmentation of the studied compounds has been proposed. An influence of the nature of leaving groups (Cl, F, CF(3), CN, COOEt), of the presence of electron withdrawing groups (Cl, F, CN, CCl(3), CF(3), COOEt) in ortho-,meta or para-positions to the leaving halogen, of the position of a dithio group toward pyridine nitrogen atom and of the role of oxygen and nitrogen in corresponding alkylxanthates and N,N-dialkyldithiocarbamates on the cyclization process has been investigated.     

Reactions of polyhalogenopyridines. 14. Reaction of isomeric dichlorocyanopyridines and pentachloropyridine with potassium ethylxanthate

The reactions of isomeric tetrachlorocyanopyridines with potassium ethylxanthate were studied. It was found that tetrachloro-2-cyanopyridine was converted successively into 4-mono- and then 3,4-bisethylxanthate derivatives. In the presence of potassium ethylxanthate the last derivative undergoes intramolecular cyclization with the formation of derivatives of 1,3-dithiolo[4,5-c]pyridine. In the case of other initial polychloropyridines processes involving substitution of the chlorine atoms by the ethylxanthate fragment, sometimes accompanied by the loss of COS molecules, were observed instead of heterocyclization. For Communication 13, see [1]. Chernogolovka Institute of Chemical Physics, Russian Academy of Sciences, Chernogolovka 142432. M. V. Lomonosov Moscow State University, Moscow 119899. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1510–1520, November, 1997.     

Reactions of Polyhalopyridines. 17. Synthesis of 2-, 3-, and 4-Perfluoroalkylthiopolychloropyridines

2-, 3-, and 4-Perfluoroalkylthiopolychloropyridines have been synthesized using perfluoroalkylated thiol and disulfide derivatives of polychloropyridines via the thermal decomposition of Xe(II) bisperfluoroalkylcarboxylates. It was shown that their formation takes place from the starting thiols only through the formation of the disulfides. It was found that 3,4,5,6-tetrachloro-2-trifluoromethylthiopyridine reacts with potassium p-tolylthiolate with retention of the fluorine containing fragment and substitution of the chlorine atom in position 4 of the pyridine ring by the tolythio group.