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Sample records for 1,3-diazines

  1. Phase transition and proton exchange in 1,3-diazinium hydrogen chloranilate monohydrate

    Energy Technology Data Exchange (ETDEWEB)

    Asaji, T., E-mail: asaji@chs.nihon-u.ac.jp; Hoshino, M. [Nihon University, Department of Chemistry, Graduate School of Integrated Basic Sciences (Japan); Ishida, H. [Okayama University, Department of Chemistry, Faculty of Science (Japan); Konnai, A. [National Maritime Research Institute, Navigation and System Engineering Department (Japan); Shinoda, Y. [Bruker AXS K. K. (Japan); Seliger, J. [University of Ljubljana, Faculty of Mathematics and Physics (Slovenia); Zagar, V. [Jozef Stefan Institute (Slovenia)

    2010-06-15

    In the hydrate crystal of 1:1 salt with 1,3-diazine and chloranilic acid (H{sub 2}ca), (1,3-diazineH){center_dot}H{sub 2}O{center_dot}Hca, an unique hydrogen-bonded molecular aggregate is formed. There exists proton disorder in the N-H...O hydrogen bond between 1,3-diazinium ion and water (H{sub 2}O) of crystallization. In order to reveal dynamic aspect of this disorder, {sup 35}Cl NQR measurements were conducted. Two resonance lines observed at 35.973 and 35.449 MHz at 321 K split into four lines below T{sub c} = 198 K clearly showing occurrence of a solid-solid phase transition; 36.565, 36.357, 36.011, 35.974 MHz at 77 K. Temperature dependence of spin-lattice relaxation time T{sub 1} in high-temperature phase was observed to obey an Arrhenius-type relation with the activation energy of 8.5 kJ mol{sup - 1}. This result leads to the conclusion that proton exchange in the N-H...O hydrogen bond takes place in the high-temperature phase. Specific heat measurements by DSC resulted in the transition entropy {Delta}S = 1.3 J K{sup - 1} per 1 mole [(1,3-diazineH){center_dot}H{sub 2}O{center_dot}Hca]{sub 2} which is far less than 2R ln2 = 11.5 J K{sup - 1} mol{sup - 1}. It is expected that proton exchange in the two hydrogen bonds within the aggregate does not occur independently but concertedly with strong correlation in the high-temperature phase.

  2. EXPERIMENTAL AND COMPUTATIONAL STUDIES OF THE FORMATION MECHANISM OF PROTONATED INTERSTELLAR DIAZINES

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhe-Chen; Cole, Callie A.; Bierbaum, Veronica M. [Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309 (United States); Snow, Theodore P., E-mail: zhwa4666@colorado.edu [Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States)

    2015-01-10

    Studies of interstellar chemistry have grown in number and complexity by both observations and laboratory measurements, and nitrogen-containing aromatics have been implicated as important interstellar molecules. In this paper, the gas-phase collision induced dissociation (CID) processes of protonated pyridazine (1,2-diazine), pyrimidine (1,3-diazine), and pyrazine (1,4-diazine) cations (C{sub 4}H{sub 5}N{sub 2} {sup +}) are investigated in detail both experimentally and theoretically. The major neutral loss for all three CID processes is HCN, leading to the formation of C{sub 3}H{sub 4}N{sup +} isomers; our density functional theory (DFT) calculations support and elucidate our experimental results. The formation of C{sub 3}H{sub 4}N{sup +} isomers from the reaction of abundant interstellar acrylonitrile (CH{sub 2}CHCN) and H{sup +}is also studied employing DFT calculations. Our results lead to a novel mechanism for interstellar protonated diazine formation from the consecutive reactions of CH{sub 2}CHCN+ H{sup +} + HCN. Moreover, our results motivate the continuing search for interstellar C{sub 3}H{sub 4}N{sup +} isomers as well as polycyclic aromatic N-containing hydrocarbons (PANHs)

  3. C-H bond strengths and acidities in aromatic systems: effects of nitrogen incorporation in mono-, di-, and triazines.

    Science.gov (United States)

    Wren, Scott W; Vogelhuber, Kristen M; Garver, John M; Kato, Shuji; Sheps, Leonid; Bierbaum, Veronica M; Lineberger, W Carl

    2012-04-18

    The negative ion chemistry of five azine molecules has been investigated using the combined experimental techniques of negative ion photoelectron spectroscopy to obtain electron affinities (EA) and tandem flowing afterglow-selected ion tube (FA-SIFT) mass spectrometry to obtain deprotonation enthalpies (Δ(acid)H(298)). The measured Δ(acid)H(298) for the most acidic site of each azine species is combined with the EA of the corresponding radical in a thermochemical cycle to determine the corresponding C-H bond dissociation energy (BDE). The site-specific C-H BDE values of pyridine, 1,2-diazine, 1,3-diazine, 1,4-diazine, and 1,3,5-triazine are 110.4 ± 2.0, 111.3 ± 0.7, 113.4 ± 0.7, 107.5 ± 0.4, and 107.8 ± 0.7 kcal mol(-1), respectively. The application of complementary experimental methods, along with quantum chemical calculations, to a series of nitrogen-substituted azines sheds light on the influence of nitrogen atom substitution on the strength of C-H bonds in six-membered rings.

  4. Chemical constituents and antioxidant activities of waste liquid extract from Apostichopus japonicus Selenka processing

    Institute of Scientific and Technical Information of China (English)

    LI Chaofeng; LI Xiancui; LI Hong; GUO Shuju; ZHU Xiaobin

    2013-01-01

    Apostichopus japonicus Selenka is an ideal tonic food that is used traditionally in many Asian countries,and it contains many bioactive substances,such as antioxidant,antimicrobial,and anticancer materials.To convert waste liquid generated during production into a useful resource,extract from waste liquid was isolated by column chromatography and studied by the pyrogallol autoxidation and 1,10-phenanthroline-Fe2+ oxidation methods.Results show that the extract scavenged about 91% of the superoxide anion radical at a concentration of 1.4 mg/mL and 24% of the hydroxyl radical at 3.3 mg/mL.Four compounds were isolated and identified from the extract:2,4-dihydroxy-5-methyl-1,3-azine; 2,4-dihydroxy-1,3-diazine; 3-O-[β-D-quinovopranosyl-(1→2)-4-O-sodium sulfate-β-D-xylopranosyl]-holosta-9(11)-ene-3β,12t,17α-triol; and 24-ethyl-5t-cholesta-7-ene-3β-O-β-D-xylopyranoside.All of these compounds are known in A.japonicus,and were found in the waste liquid for the first time.