The synthesis of 4H-imidazo[5,1-c][1,4]benzothiazine derivatives

A facile synthesis of the 4H-imidazo[5,1-c][1,4]benzothiazine ring system is described. The synthesis utilized the annulation of an imidazole ring onto a 2H-1,4-benzothiazin-3(4H)-one via the addition of the anion of ethyl isocyanoacetate. Methods for the functionalization of the 1-, 3-, 4-, and 5-positions of the ring system are presented.     

Trace analysis of halocarbons in water; Direct aqueous injection with electron capture detection

Interest in monitoring halogenated organics in drinking water and natural surface and ground water in the low ppb range continues to grow. There is a tendency to include still more volatile halocarbons, the trace determination of which is known to be rather demanding. This prompted us to re-examine the feasibility of large-volume direct aqueous injection onto capillary columns, coupled with ECD. A primary problem was to avoid simultaneous elution of water with halocarbons, since water suppresses the ground current of the ECD. The following measures contributed to the solution of this problem. Apolar, extremely inert, columns are required to elute water completely, and even before very light halocarbons. Their coatings have to be far thicker (≈? 5 mUm) than commonly employed thick films since they must permit isothermal analysis at a column temperature around 100°C in order to ensure rapid and complete elution of water. Finally, it is essential that sampling be carried out on-column for two reasons: diffusion of water vapor in the injector, resulting in delayed elution, is then eliminated, and peak distortion during splitless injection is avoided. Although we now know that persilylated columns with immobilized coatings withstand routine water injections, more longterm experience is needed to provide detailed recommendations for the handling of these columns.     

Pyridine N-sulfides. Benzisothiazolo[2,3-a]pyridinium tetrafluoroborates and benzothiopheno[3,2-b]pyridines. Novel heterocyclic systems

2-(2-Mercaptophenyl)pyridines are prepared from the corresponding phenols and oxidized with N-chloro-succinimide and silver tetrafluoroborate to benzisothiazolo[2,3-a]pyridine salts ( 4 ). The latter do not rearrange thermally or photochemically to benzothiopheno[3,2-b)pyridines ( 19 ) and are attacked by nucleophiles at sulfur rather than in the pyridine ring, to give the original 2-(2-mercaptophenyl)pyridine back in a reaction involving a dismutation. 19 is prepared by rearranging O-[2-(3-bromo-2-pyridyl)-4-nitrophenyl]dimethylthio-carbamate to the S-aryl compound and heating the latter with strong base.     

Pion structure function from low-p T hadron production

The recombination model for low-p _T inclusive reactions is extended to the meson fragmentation region. Some basic issues in the model are rrexamined, and the differences between the proton and pion initiated reactions are stressed. By applying the model to theπ ⁺ p→K ⁺ X reaction, the fast valence quark distribution in the pion is extracted. Our best fit to the data yieldsF _q ^π (x)～(1?x)^0.8±0.2 for largex.     

Tau neutrino mass from semileptonic decays

The semileptonic three particle decays of the tau provide determinations of the tau neutrino mass. The shift of the maximal energy of the observable final state particles islinear in the neutrino mass. The endpoint energy of the pion and a partially integrated decay rate in τ → πωv _τ and τ → πρV _τ are sensitive to a neutrino mass smaller than 100 MeV. Thus, the present bound on \(m_{v_\tau } \) can significantly be improved.     

Plasma polymerization anda-C:H film ablation in microwave discharges in methane diluted with argon and hydrogen

Neutral hydrocarbons are observed from a microwave discharge in a fast flow of (A) 0.5–6% methane in argon, (B) 0.5–6% methane in hydrogen, and (C) hydrogen over a previously depositeda-C:H film. System (A) produces polyacetylenic and other hydrocarbons through C₈ by predominantly gas-phase reactions and deposits ana-C: H film. Reactions under conditions (B) and (C) produce hydrocarbon radicals and molecules with masses through 300 that in case (B) arise from both gas-phase reactions and film ablation, and in case (C) from film ablation alone. Proposals are made for the mechanisms of gas-phase polymerization, film deposition, and ablation. Hydrocarbon ions observed downstream from these discharges appear to arise from ionization of neutral species with a distribution determined by subsequent ion-molecule reactions and selective diffusion losses.Work supported by NSF Grant CHE-87-21744.     

Determination of organic substances by standard chromous chloride solution

The reducibility of a number of organic compounds by a standard chromous chloride solution, prepared determinately from potassium dichromate, has been studied. Orange II, tartrazine, and azoxybenzene (after rearrangement in sulfuric acid medium to the corresponding azo compound) were quantitatively cleaved to the corresponding amines, while azobenzene was reduced only to hydrazobenzene (extent of reduction uncertain). Also quantitatively reduced were: propiolic acid to propenoic acid, diacetyl to acetoin, and benzil to benzoin. Hydrazobenzene, diphenylacetylene, 2-methyl-3-butyn-2-ol, 1-ethynyl-cyclohexanol-1, 2,5-dimethyl-3-hexyne-2,5-diol, 2,5-diphenyl-3-hexyne-2,5-diol, and acetylacetone were not reduced even at elevated temperatures.     

Die Bestimmung des Sauerstoffgehaltes in Silizium nach Ionenimplantation durch eine SiO2-Deckschicht mit Hilfe der Reaktion18O(p, α)15N

The recoil implantation yield of oxygen atoms recoiled from¹⁸O-enriched SiO₂ layers into silicon substrates has been studied using the¹⁸O(p, α)¹⁵N nuclear reaction. The method to determine the number of oxygen atoms in silicon is described in detail and the results are compared to the theoretical predictions.