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Lorenzo CaggianoDamiano Castoldi Raphael BeumerPau Bayón Joachim TelserCesare Gennari 《Tetrahedron letters》2003,44(43):7913-7919
During the course of our synthetic studies towards simplified eleuthesides, we have found that p-methoxyphenyl (PMP) protected allylic alcohols are compatible with the RCM reaction and can give better yields than the corresponding free allylic alcohols. 相似文献
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Depecker G Patino N Di Giorgio C Terreux R Cabrol-Bass D Bailly C Aubertin AM Condom R 《Organic & biomolecular chemistry》2004,2(1):74-79
A cyclic molecule including a hexameric PNA sequence has been designed and synthesized in order to target the TAR RNA loop of HIV-1 through the formation of a "kissing complex". For comparison, its linear analogue has also been investigated. The synthesis of the cyclic and linear PNA has been accomplished following a liquid-phase strategy using mixed PNA and fully N-protected (aminoethylglycinamide) fragments. The interactions of this cyclic PNA and its linear analogue with TAR RNA have been studied and the results indicate clearly that no interaction occurs between the cyclic antisense PNA and TAR RNA, whereas a tenuous interaction has been detected with its linear PNA analogue. 相似文献
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Based on theoretical thermodynamic principles, the possibility of environmental degradation of polyacrylamide to its starting monomer was investigated. Theoretical electronic structure studies on the geometry and fragmentation energy of acrylamide and N,N‐dimethyl acrylamide tetramer models were carried out using a first principles gradient corrected density functional approach. Thermal degradation to form a radical would require the cleavage of carbon–carbon bonds in the polymer chain; the energy needed for this cleavage was found to depend on the structure of the repeat unit which ranged from low of 72.5 kcal for a rare head‐to‐head construct to 86.2 kcal for a normal head‐to‐tail polymer construct (therefore, for the cleavage of a normal head‐to‐tail repeat unit, temperatures of approximately 450°C would be required). The thermodynamics of the unzipping, disproportionation, and back‐biting reactions in the resulting radical fragments were also investigated; the back‐biting process was found to require the least energy and provided the most stable radical fragment with a low probability for disproportionation or releasing of monomer to occur. The effect of solvation on the hydrogen‐bonding network in the acrylamide tetramer was studied by adding explicit molecules of water to the tetramer models. The addition of water had a significant effect on the stability of the model polymer slightly stabilizing the head‐to‐head polymer, and slightly destabilizing the head to tail polymer. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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K. Raha Mrs P. S. Makashir E. M. Kurian 《Journal of Thermal Analysis and Calorimetry》1989,35(4):1173-1179
The kinetics of the initial stage of thermal decomposition of N-2,4,6 tetranitro-N-methyl aniline (tetryl) in condensed state has been investigated by high temperature infrared spectroscopy (IR) in conjunction with pyrolysis gas analysis and thermogravimetry (TG). The decomposition in KBr matrix in the temperature range of 131 to 145 °C shows rapid decrease in the N-NO2 band intensity as compared to the C-NO2 band. Decomposition products in the initial stage show mainly NO2 gas and picric acid. The studies show that the initial stage of decomposition of tetryl occurs by the rupture of the N-NO2 bond and the energy of activation for this process is 177 kJ/mol.
Zusammenfassung Mittels Hochtemperatur-IR-Spektroskopie wurde in Verbindung mit Pyrolysengasanalyse und Thermogravimetrie (TG) die Kinetik des einleitenden Schrittes der thermischen Zersetzung von N-2,4,6-Tetranitro-N-Methylanilin (Tetryl) im kondensierten Zustand untersucht. Die Zersetzung in einer KBr-Matrix im Temperaturbereich von 131–145 °C äußert sich in einem schnellen Abnehmen der Intensität der N-NO2 Bande bezogen auf die der C-NO2 Bande. Zersetzungsprodukte des einleitenden Schrittes sind hauptsächlich NO2 Gas und Pikrinsäure. Die Untersuchungen zeigten, daß der einleitende Schritt der Zersetzung von Tetryl die Spaltung der N-NO2 Bindung ist. Die Aktivierungsenergie für diesen Prozess beträgt 177 kJ/mol.
N-2,4,6-N- () , . 131–145 °C N-NO2 C-NO2. . , N-NO2, 177 /.相似文献
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Luís Antônio Dantas Silva Fernanda Vieira Teixeira Raphael Caixeta Serpa Najla Locatelli Esteves Rayane Ramos dos Santos Eliana Martins Lima Marcílio Sérgio Soares da Cunha-Filho Adriano Antunes de Souza Araújo Stephânia Fleury Taveira Ricardo Neves Marreto 《Journal of Thermal Analysis and Calorimetry》2016,123(3):2337-2344
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