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1

The Relationship Between the Heats of Formation and the Molecular Electrostatic Potentials of Polyazaarenes

Bartošková M., Friedl Z.

Central European Journal of Energetic Materials

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2013

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Vol. 10, no. 1

103--112

EN

In order to characterize the explosive properties of high-nitrogen, energetic compounds, the heats of formation, either in the gas or the solid state, are often used as preliminary data. Their relationship to the number of nitrogen atoms involved is usually known, so exploring it cannot furnish any new information. However, the very promising, quantitative structure property relationship (QSPR) approach utilizes the molecular surface electrostatic potential V(r). We have therefore performed calculations for 12 azines and 10 azoles by the DFT B3PW91/cc-pVTZ method, and constructed their gas phase heats of formation Δf H°(298,g) by means of the isodesmic reaction approach. The acquired gas phase heats of formation Δf H°(298,g) were correlated with the molecular surface electrostatic potentials VS,max, VS,min, and VS(ring), which were calculated by the B3LYP/6-31G(d,p)//B3PW91/cc-pVTZ method. It is shown that the VS(ring) electrostatic potential describes very precisely the structures of high-nitrogen N-heteroaromatics, with both consecutive and isolated nitrogen atoms, and their thermodynamic properties.

2

15N NMR Coordination Shifts in Transition Metal Chloride Complexes with Azines versus Type of Central Ion

Pazderski L.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 7

1083-1093

EN

15N NMR coordination shift is the difference between the 15N chemical shift of the concerned nitrogen atom in the complex and ligand molecules (Delta coord 15N =delta compl 15N - delta lig 15N ). Themeasurements, convenient for complexes with diamagnetic transition metal ions, allow to determinemetallation siteswithin potentially ambidentateN-donor heterocycles. In case of azines, the 15N coordination shifts of pyridine-type nitrogens are usually negative, i.e. the shielding is observed. Variable low-frequency 15N coordination shifts (ca. 70-140 ppm) were noted for a number of chloride complexes of Pd(II), Pt(II), Au(III), Pd(IV), Pt(IV), Co(III), Rh(III) and Zn(II) with pyridine, 2,2'-bipyridine, 1,10-phenanthroline, 2,2'-biquinoline, purine and 1,2,4-triazolo-[1,5a]-pyrimidine(s). Some dependencies between the magnitude of the shielding effect and such features of the concerned complex as the type of central ion, its electron configuration (oxidation state) and the coordination sphere geometry were discussed.

3

Tandem pericyclic reactions in synthesis of azines. Part I. PM3 study of thermal behavior of 1-aza-1,3,5-hexatrienes

Suwiński J., Mohamed M.

Zeszyty Naukowe. Chemia / Politechnika Śląska

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2002

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z. 147

5-13

EN

This paper presents results of PM3 calculations of the disrotatory thermal electrocyclization of several simple azahexatrienes and a short review of selected papers concerning formation of azines in thermal processes starting from aza-1,3,5-hexatriene derivatives and occurring, we believe, as tandem pericyclic processes involving disrotatory electrocyclization followed by a concerted elimination or other thermal reactions. The results of calculations in some cases support the mechanistic propositions based on the results of synthetic experiments, in the other ones they seem to deny them, pointing out to pericyclic processes.

PL

W pracy przedstawiono wyniki obliczeń metodą PM3 dysrotacyjnej termicznej elektrocyklizacji szeregu prostych azaheksatrienów i krótki przegląd wybranych prac dotyczących tworzenia azyn w termicznych procesach wychodząc z aza-1,3,5-heksatrienu lub jego pochodnych i zachodzących, jak sądzimy, zgodnie z mechanizmem dysrotacyjnej elektrocyklizacji wraz z następczą uzgodnioną eliminacją lub innym termicznym procesem. Wyniki naszych obliczeń w niektórych przypadkach potwierdzają mechanizmy proponowane na podstawie eksperymentów, w innych wydają się im zaprzeczać, wskazując na procesy pericykliczne.

4

The reactions of 2--(Chloroseleno)benzoyl Chloride with Pyridine and Related Azines

Osajda M., Młochowski J.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 7

953-958

EN

The reaction of 2-(chloroseleno)benzoyl chloride with pyridine and pyridine-like heterocycles such as pyrimidine, pyrazine, quinoline, phthalazine, phenazine and 1,10-phenanthroline was studied. In the most cases stable 2-(hydroxyseleno)benzoylazinium chlorides were produced depending on the number of the pyridinium-like nitrogen atoms and their situation in the ring system.