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61.
Elena Stashenko Hughes Wiame Stephane Dassy Jairo Ren Martinez Takayuki Shibamoto 《Journal of separation science》1995,18(1):54-58
The oil extracted from the trunk of the copaiba tree (Copaifera officinalis) is composed of sesquiterpenes, C15H24, and a small amount (>7 %) of sesquiterpenols, C15H26O; these were identified from their Kováts indices and mass spectra. The use of zeolites in the catalytic transformation of this renewable source of hydrocarbons is of interest in the search for new chemicals and ecologically clean fuels. Oil samples from copaiba trees growing in Colombia's Oriental Plains were circulated over zeolite ZSM-5 in a continuous flow fixed-bed micro reactor at 225, 265, and 325°C, for 1 h and subsequently analyzed by HRGC and GC-MS. Whereas only thirty four sesquiterpenes were identified in the original oil, over two hundred compounds were found in the product of the treatment of copaiba oil with zeolite ZSM-5. This complex mixture of sesquiterpenes, light aromatic compounds, and indene and naphthalene derivatives resulted from reactions such as isomerization, hydrogenation, cracking, and dehydrogenation with and without cracking. The amount of cracking products and aromatic compounds increased with reactor temperature but decreased with catalyst aging. 相似文献
62.
Duvernay F Trivella A Borget F Coussan S Aycard JP Chiavassa T 《The journal of physical chemistry. A》2005,109(49):11155-11162
The UV isomerization of formamide (HCONH2) trapped in xenon, nitrogen, argon, and neon cryogenic matrices has been monitored by Fourier transform infrared (FT-IR) spectroscopy. Formamide monomer is the only species present in the matrices after deposition; when UV-selective irradiation was carried out at 240 nm, the n --> pi transition allowed us to observe the formation of several isomers of formimidic acid [H(OH)C=NH]. On these latter species, we carried out selective IR irradiation of their OH stretching mode and compared the experimental and theoretical (B3LYP/6-311+G(2d,2p)) sets of bands. This study allowed us to characterize for the first time all the isomers of formimidic acid. We have then studied the vacuum UV photodecomposition (lambda > 160 nm) of this molecule at 10 K in argon and xenon matrices. Several primary photoproducts such as HCN.H2O, HNC.H2O, and HNCO.H2 complexes, yielded by dehydration and dehydrogenation processes, were characterized. 相似文献
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65.
Pedersen DB Zgierski MZ Denommee S Simard B 《Journal of the American Chemical Society》2002,124(23):6686-6692
An Al-cytosine association complex has been generated via laser ablation of a mixture of aluminum and cytosine powders that were pressed into a rod form. The ionization energy of the complex is found to be 5.16 +/- 0.01 eV. The photoionization efficiency spectrum of Al-cytosine has also been collected. DFT calculations indicate that binding of Al to cytosine manifests a significant weakening of the N-H bond, predicted to have a strength of 1.5 eV in the complex, and a significant stabilization of the oxo tautomeric form relative to the hydroxy forms. The predicted ionization energy of 5.2 eV agrees well with the experimental value. The threshold for dehydrogenation/ionization of Al-cytosine, forming (Al-cytosine-H)+, is found to occur at photoexcitation energies between 11.4 and 12.8 eV. This is a two-photon process that is proposed to occur via photoinduced electron transfer from Al to an antibonding (sigma) orbital localized on N-H. In the context of this mechanism, this work constitutes the first time charge transfer between a metal and DNA base has been photoinitiated in the gas phase. 相似文献
66.
Brough P Klumpp C Bianco A Campidelli S Prato M 《The Journal of organic chemistry》2006,71(5):2014-2020
Eight members of a new family of fullerene derivatives, [60]fulleropyrrolidine-N-oxides, have been synthesized and characterized. Facile oxidation, by a peracid, of the parent [60]fulleropyrrolidine gave clean conversions into the product molecules, in which the tertiary amine is transformed into a quaternary amine bearing an oxygen atom. The reaction is very selective, favoring the nitrogen atom of the pyrrolidine ring in preference to epoxidation of the fullerene cage. The 1H NMR shows an AB quartet splitting pattern, characteristic of nonequivalent hydrogens in the pyrrolidine ring and at a chemical shift displacement of 0.8 ppm downfield. Other methods of characterization are described, including MS, differential scanning calorimetry, thermogravimetric analysis, HPLC, UV/vis, and IR. Conclusive evidence for the formation of an N-oxide moiety is provided by the synthesis, oxidation, and NMR characterization of a novel [60]fulleropyrrolidine containing a 15N isotope, showing an 85 ppm downfield heteroatom chemical shift. Preliminary details of the effects of substitution on the reactivity of the pyrrolidine ring are also reported. 相似文献
67.
Konstantinos Ghirtis Nicole Pouli Panagiotis Marakos Alexios‐Leandros Skaltsounis Stephane Leonce Ghanem Atassi Daniel H. Caignard 《Journal of heterocyclic chemistry》2001,38(1):147-152
As part of a research program directed towards the design and synthesis of pyranoxanthones structurally related to acronycine, we present here the synthesis and cytotoxic activity of the pyranoxanthones 3 and 4 (X= H, Br; R= H, OMe; R'= H, Ac). Some of these compounds inhibit L1210 cell proliferation. 相似文献
68.
Stephane LeconteRenzo Ruzziconi 《Journal of fluorine chemistry》2002,117(2):167-172
Regioisomerically pure trifluoromethyl- and trifluoromethoxy-substituted aromatic and heteroaromatic aldehydes and carboxylic acids are valuable building blocks for the synthesis of biologically active molecules. They have been prepared by employing modern organometallic methods. On this basis, a novel access to 2,3-dihydro-5-(trifluoromethoxy)indole was developed which represents an intriguing example of how organometallic and radical chemistry can fecundate each other. 相似文献
69.
Stephane Laederich 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1991,42(2):264-279
In this paper we will be interested in the behaviour of long chains of coupled gravitational pendula. We will prove existence and uniqueness of periodic solutions for such chains under periodic forcing and will prove that under some smoothness assumptions the chain behaves as an uncoupled one. We will also analyse a more general class of differential difference equations and prove existence and unicity results for periodic solutions.Research partially supported by AFOSR under U.R.I, contract F49620-86-C-0131 to Northeastern University. 相似文献
70.
Stephane?DanieleEmail author Liliane?G.?Hubert-Pfalzgraf 《Journal of Sol-Gel Science and Technology》2005,35(1):57-64
The reactions between La3(OBut)9(HOBut)2 and various trimethylsilylamide species M[N(SiMe3)2] x(THF)y (M = K, Ba, Pb) have been investigated as a means to acceed to heterometallic La-M species. The La-K derivative was used as synthon in metathesis reaction toward CuCl2 in order to get an heterometallic La-Cu derivative. All compounds were characterized by elemental analysis, FT-IR, EPR and multinuclear NMR spectroscopies. Their hydrolyses at room temperature in THF led to nanocrystalline doped-lanthanum hydroxides. The as-prepared materials were characterized by elemental analysis, XRD and TEM. Their thermal behavior was studied by XRD and compared with that of yttrium derivatives. 相似文献