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61.
62.
Marta Lenartowicz Andrzej Swinarew Grażyna Rymarz 《International Journal of Polymer Analysis and Characterization》2014,19(7):611-624
The article presents the impact of long-term (10 years of maintenance) use of polymer material, with the result of a gradual loss of primary physical and chemical properties and degradation. Under the influence of factors such as heat, water, sunlight, stress forces, sulfur oxides, nitrogen oxides, oxygen, metals, and microorganisms, polymers experience irreversible structural changes that cause a decrease in molecular weight or change in chemical composition. The problems mentioned in this article are known worldwide because of many possible applications for wide-area covers, roofing and others. 相似文献
63.
64.
Helicenophyrins: Expanded Carbaporphyrins Incorporating Aza[5]helicene and Heptacyclic S‐Shaped Aza[5]helicene Motifs 下载免费PDF全文
Dr. Bartosz Szyszko Monika Przewoźnik Dr. Michał J. Białek Dr. Agata Białońska Prof. Dr. Piotr J. Chmielewski Dr. Jakub Cichos Prof. Dr. Lechosław Latos‐Grażyński 《Angewandte Chemie (International ed. in English)》2018,57(15):4030-4034
Incorporation of phenanthrene into a hexaphyrin(1.1.1.1.1.0) frame resulted in intramolecular ring fusion, thus giving rise to chiral helicenophyrins. These molecules contain helicene and porphyrin features by incorporating either an aza[5]helicene or heptacyclic S‐shaped aza[5]helicene. 相似文献
65.
Cobalt‐Catalyzed Electrophilic Amination of Aryl‐ and Heteroarylzinc Pivalates with N‐Hydroxylamine Benzoates 下载免费PDF全文
Dr. Yi‐Hung Chen Simon Graßl Prof. Dr. Paul Knochel 《Angewandte Chemie (International ed. in English)》2018,57(4):1108-1111
Aryl‐ and heteroarylzinc pivalates can be aminated with O‐benzoylhydroxylamines at 25 °C within 2–4 h in the presence of 2.5–5.0 % CoCl2?2 LiCl to furnish the corresponding tertiary arylated or heteroarylated amines in good yields. This electrophilic amination also provides access to diarylamines and aryl(heteroaryl)amines. A new tuberculosis drug candidate (Q203) was prepared in six steps and 56 % overall yield by using this cobalt‐catalyzed amination as the key step. 相似文献
66.
A. Gehring S. Goy P. Müller O. Roos Br. Tacke Th. Arnd J. von Csiky G. von Eperjessy H. Kappen R. A. Kutschinsky S. T. Jensen St Kühn S. N. Aleschin O. Lemmermann J. König J. Hasenbäumer A. A. J. v. 'Sigmond A. Němec H. Neubauer L. Dworak K. Hesse M. Gračanin Hempelmann L. Fresenius H. Fischer E. Blanck W. Jessen W. Lesch E. Hoffmann B. Dirks F. Scheffer E. Becker R. Balks H. Elleder M. Gerlach Th. Römer A. Densch E. A. Mitscherlich H. Vageler R. Meyer H. Opitz K. H. Rathsack H. Niklas H. Poschenrieder J. Trischler J. Lanik Anna Koppová O. Wehrmann O. Eckstein A. Jacob G. N. Hoffer 《Analytical and bioanalytical chemistry》1932,90(11-12):456-480
67.
Michael Zirbes Dr. Tobias Graßl Rieke Neuber Prof. Dr. Siegfried R. Waldvogel 《Angewandte Chemie (International ed. in English)》2023,62(14):e202219217
Lignin, the world's largest resource of renewable aromatics, with annually roughly 50 million tons of accruing technical lignin, mainly Kraft lignin, is highly underdeveloped regarding the production of monoaromatics. We demonstrate the oxidative depolymerization of Kraft lignin at 180 °C to produce vanillin 1 in yields up to 6.2 wt % and 92 % referred to the maximum yield gained from the quantification reaction utilizing nitrobenzene. Using peroxodicarbonate (C2O62−) as “green” oxidizer for the degradation, toxic and/or harmful reagents are prevented. Also, the formed waste can serve as makeup chemical in the pulping process. Na2C2O6 is synthesized in an ex-cell electrolysis of aqueous Na2CO3 at BDD anodes, achieving a yield of Na2C2O6 with 41 %. At least, the oxidation and degradation of Kraft lignin is analysis via UV/Vis and NMR spectroscopy. 相似文献
68.
Incorporation of a Phenanthrene Subunit into a Sapphyrin Framework: Synthesis of Expanded Aceneporphyrinoids 下载免费PDF全文
Dr. Bartosz Szyszko Marcin Małecki Dr. Anna Berlicka Michał J. Białek Dr. Agata Białońska Kamil Kupietz Dr. Ewa Pacholska‐Dudziak Prof. Lechosław Latos‐Grażyński 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(22):7602-7608
32‐Hetero‐5,6‐dimethoxyphenanthrisapphyrins—macrocycles that link structural features of polycylic aromatic hydrocarbons and expanded porphyrins—were obtained in a straightforward [3+1] condensation reaction of dimethoxyphenanthritripyrrane and 2,5‐bis(arylhydroxymethyl)heterocyclopentadienes. The highly folded conformation of formally 4 n π‐electron macrocycles causes them to manifest only limited macrocyclic π conjugation as explored by means of NMR spectroscopic and X‐ray structural analyses, and supported by DFT calculations. Although protonation does not change their π‐conjugation characteristics, the cleavage of ether groups at the phenanthrenylene moiety yields nonaromatic 32‐hetero‐5,6‐dioxophenanthrisapphyrins. 相似文献
69.
A series of 2,2'-bipyrroles has been efficiently synthesized using an improved synthetic approach based on Pd(0)-catalyzed homocoupling of various 2-iodopyrroles. This new synthetic approach takes place at room temperature and in the presence of water. Functional groups such as formyl, ester, and nitrile are able to survive these reaction conditions. Solvents are found to play an important role in this reaction. 相似文献
70.
There has been a lasting discussion in the literature on the validity of Fourier's heat conduction law. The main concern
is the inherent infinite propagation velocity of temperature changes. Some authors hold that due to this problem the law should
fail for certain materials or on extreme time scales. Then, to reconcile experiment with theory Fourier's equation would need
an extension to a hyperbolic form. To contribute to this matter we report on unsteady heat conduction experiments in wet sand
for which hyperbolic behaviour (Kaminski 1990) was documented. Our results clearly salvage Fourier's law without giving any
explanation on why a theory with a serious inconsistency can work so well.
Received on 3 November 1998 相似文献