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1.
Carbohydr Polym ; 142: 189-98, 2016 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-26917390

RESUMO

The aim of this study was to develop a quick reaction that had high activity with a small amount of catalyst, which could be an eco-friendly alternative technique for the synthesis of biarlys in Suzuki coupling reactions. First, a novel chitosan Schiff base supported Pd(II) catalyst was synthesized, and its structure was illuminated with FTIR, (1)H NMR, (13)C NMR, TG/DTG, SEM/EDAX, XRD, ICP-OES, UV-vis, magnetic moment, and molar conductivity techniques. Subsequently, the catalytic activity of the catalyst was tested in Suzuki C-C reactions under microwave irradiation using a solvent-free reaction condition. The catalytic tests showed an excellent activity with a small load of the catalyst (0.02 mol%) in 4 min. The catalyst showed seven runs without loss of activity, and high values of turnover numbers (TON) and turnover frequency (TOF) were obtained. The novel biopolymer supported Pd(II) catalyst provided much faster reaction times, higher yields, and reusability under microwave heating compared to classic heating methods.


Assuntos
Quitosana/química , Química Verde/métodos , Paládio/química , Hidrocarbonetos Policíclicos Aromáticos/síntese química , Catálise , Química Verde/economia , Micro-Ondas , Hidrocarbonetos Policíclicos Aromáticos/química , Bases de Schiff/química
2.
J Am Chem Soc ; 136(10): 3764-7, 2014 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-24579565

RESUMO

A straightforward strategy has been used to construct large BN-embedded π-systems simply from azaacenes. BN heterosuperbenzene derivatives, the largest BN heteroaromatics to date, have been synthesized in three steps. The molecules exhibit curved π-surfaces, showing two different conformations which are self-organized into a sandwich structure and further packed into a π-stacking column. The assembled microribbons exhibit good charge transport properties and photoconductivity, representing an important step toward the optoelectronic applications of BN-embedded aromatics.


Assuntos
Hidrocarbonetos Policíclicos Aromáticos/química , Compostos Aza/química , Técnicas de Química Sintética/economia , Técnicas de Química Sintética/métodos , Desenho de Equipamento , Modelos Moleculares , Conformação Molecular , Hidrocarbonetos Policíclicos Aromáticos/síntese química , Transistores Eletrônicos
3.
J Geophys Res ; 105(B1): 539-59, 2000 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-11543291

RESUMO

The possibility for abiotic synthesis of condensed hydrocarbons in cooling/diluting terrestrial volcanic gases has been evaluated on the basis of the consideration of metastable chemical equilibria involving gaseous CO, CO2, H2 and H2O. The stabilities of n-alkanes and polycyclic aromatic hydrocarbons (PAHS) have been evaluated for several typical volcanic gas compositions under various conditions for cooling/diluting of quenched volcanic gas. The modeling shows that n-alkanes and PAHs have a thermodynamic potential to form metastably from H2 and CO below approximately 250 degrees C within the stability field of graphite. Despite the predominance of CO2 in volcanic gases, synthesis of hydrocarbons from CO2 and H2 is less favored energetically than from CO and H2. Both low temperature and a high H/C atomic ratio in volcanic gas generally favor stability of hydrocarbons with higher H/C ratios. PAHs are thermodynamically stable at temperatures approximately 10 degrees -50 degrees C higher than large n-alkanes; however, at lower temperatures, PAHs and n-alkanes have similar stabilities and are likely to form metastable mixtures. Both the energetic drive to form hydrocarbons and possible temperatures of formation increase as the oxidation state (fO2) of the volcanic gases decreases and as the cooling/dilution ratios of volcanic gases increase. Synthesis of hydrocarbons is energetically more likely in cooling trapped gases than in ashcloud eruptive columns. Mechanisms for hydrocarbon formation may include Fischer-Tropsch-type synthesis catalyzed by magnetite from solid volcanic products. On the early Earth, Mars, and Jupiter's satellite Europa, several factors would have provided more favorable conditions for hydrocarbon synthesis in volcanic gases than under current terrestrial conditions and might have contributed to the production of organic compounds required for the emergence of life.


Assuntos
Alcanos/síntese química , Evolução Química , Hidrocarbonetos/síntese química , Hidrocarbonetos Policíclicos Aromáticos/síntese química , Erupções Vulcânicas/análise , Dióxido de Carbono/química , Monóxido de Carbono/química , Planeta Terra , Evolução Planetária , Hidrogênio/química , Oxirredução , Planetas , Temperatura , Água/química
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