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31.
The oxidation of perfluorobutene‐2 (C4F8) initiated by trifluoromethyl hypofluorite (CF3OF) in presence of O2 has been studied at 323.1, 332.6, 342.5, and 352.0 K, using a conventional static system. The initial pressure of CF3OF was varied between 4.8 and 23.6 Torr, that of C4F8 between 48.7 and 302.4 Torr, and that of O2 between 51.5 and 270.4 Torr. Several runs were made in presence of 325.5–451.2 Torr of N2. The main products were COF2, CF3C(O)F, and CF3OC(O)F. Small amounts of compound containing ? CF(CF3)? O? C(O)CF3 group were also formed, as detected by 13C NMR spectroscopy. The oxidation is a homogeneous short‐chain reaction, attaining, at the pressure of O2 used, the pseudo‐zero‐order condition with respect to O2 as reactant. The reaction is independent of the total pressure. Its basic steps are as follows: the thermal generation of CF3O? radicals by the abstraction of fluorine atom of CF3OF by C4F8, the addition of CF3O? to the alkene, the formation of perfluoroalkoxy radicals RO? in presence of O2, and the decomposition of these radicals via the C? C bond scission, giving products containing ? C(O)F end group and reforming RO? and CF3O? radicals. The mechanism consistent with experimental results is postulated. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 532–541, 2003 相似文献
32.
Existence and Uniqueness of Fixed Point in Partially Ordered Sets and Applications to Ordinary Differential Equations 总被引:1,自引:0,他引:1
We prove some fixed point theorems in partially ordered sets, providing an extension of the
Banach contractive mapping theorem. Having studied previously the nondecreasing case, we consider
in this paper nonincreasing mappings as well as non monotone mappings. We also present some
applications to first–order ordinary differential equations with periodic boundary conditions, proving
the existence of a unique solution admitting the existence of a lower solution.
Research partially supported by Ministerio de Educación y Ciencia and FEDER, Project MTM2004-06652-C03-01, and by Xunta de
Galicia and FEDER, Projects PGIDIT02PXIC20703PN and PGIDIT05PXIC20702PN 相似文献
33.
We find sufficient conditions for the boundness of every solution of first-order fuzzy differential equations as well as certain fuzzy integral equations. Our results are based on several theorems concerning crisp differential and integral inequalities. 相似文献
34.
Comelli NC Lobayan RM Castro EA Jubert AH 《The journal of physical chemistry. A》2011,115(9):1686-1700
The conformational and electronic characteristics of the polar O(9)═C(8)-X(10) moiety in the anticonvulsant valproic acid (Vpa) drug and some of their amides and ester derivatives are analyzed at the B3LYP level using the 6-31+G(d,p) and 6-311++G(d,p) 6d,10f basis sets. Exploring the delocalization of the electron density of the O(9)═C(8)-X(10) moiety by means of ELF, NBO, and AIM calculations, we found that the bending away from coplanarity of the atoms in O(9)═C(8)-X(10) is accompanied by a three-dimensional arrangement of donor and acceptor proton units closing nearly planar pseudorings of four, five, and six members arising from stabilizing interactions around the O(9)═C(8)-X(10) backbone. From the structure-property relationship analysis, we explain the origin of the change in the structural parameters and atomic charges in the polar moiety. 相似文献
35.
The challenging separation of regioisomers and enantiomers of monoacylglycerols (MAGs) of fatty acids has been achieved using a single chiral HPLC column (Chiralpak® IC or Chiralpak® IA) and hexane/2‐propanol eluent mixtures, without previous derivatization of the samples. The efficacy of the method is independent of the chain length and the degree of unsaturation of the fatty acids of the MAG. In addition, the separation method allows monitoring the time course for the loss of enantiomeric purity of the fatty acid‐derived MAGs in polar hydroxylic solvents. 相似文献
36.
37.
Tobón YA Nieto LI Romano RM Della Védova CO Downs AJ 《The journal of physical chemistry. A》2006,110(8):2674-2681
The photolytically induced reactions of a dihalogen XY (= Cl2, ICl, or IBr) with OCS isolated together in an Ar matrix at about 15 K lead to different photoproducts depending on the natures of X and Y. In addition to the known species ClCO*, OCCl2, syn-ClC(O)SCl, syn-ClC(O)SSCl, IC(O)Cl, IC(O)Br, and syn-BrC(O)SBr, syn-iodocarbonylsulfenyl bromide, syn-IC(O)SBr, has thus been identified for the first time as a photoproduct of the reactions involving IBr. The first product to be formed in the reactions with Cl2 or ICl is the ClCO* radical which reacts subsequently with halogen or sulfur atoms or other matrix guests to give the corresponding carbonyl dihalide (OCCl2 and IC(O)Cl), syn-ClC(O)SCl or syn-ClC(O)SSCl. The analogous reaction with IBr affords syn-BrC(O)SBr, IC(O)Br, and syn-IC(O)SBr. The changes have been followed, the products characterized experimentally by IR measurements, and the spectra analyzed in the light of the results of appropriate theoretical calculations. 相似文献
38.
Hydrogen peroxide (H2O2) present in honey was rapidly determined by the differential amperometric method in association with flow-injection analysis (FIA) and a tubular reactor containing immobilized enzymes. A gold electrode modified by electrochemical deposition of platinum was employed as working electrode. Hydrogen peroxide was quantified in 14 samples of Brazilian commercial honeys using amperometric differential measurements at +0.60V vs. Ag/AgCl((sat)). For the enzymatic consumption of H2O2, a tubular reactor containing immobilized peroxidase was constructed using an immobilization of enzymes on Amberlite IRA-743 resin. The linear dynamic range in H2O2 extends from 1 to 100 x 10(-6) mol L(-1), at pH 7.0. At flow rate of 2.0 mL min(-1) and injecting 150 microL sample volumes, the sampling frequency of the 90 determinations per hour is afforded. This method is based on three steps involving the flow-injection of: (1) the sample spiked with a standard solution, (2) the pure sample and (3) the enzymatically treated sample with peroxidase immobilized. The reproducibility of the current peaks for hydrogen peroxide in 10(-5) mol L(-1) range concentration showed a relative standard deviation (R.S.D.) better than 1%. The detection limit of this method is 2.9 x 10(-7) mol L(-1). The honey samples analyses were compared with the parallel spectrophotometric determination, and showed an excellent correlation between the methods. 相似文献
39.
Jerome Lozada Wen Xuan Lin Rosana M. Cao-Shen Ruyin Astoria Tai Prof. David M. Perrin 《Angewandte Chemie (International ed. in English)》2023,62(16):e202215371
Tetrafluoroborate (BF4−) has long been used as a spectator counter anion. Herein, we report an unprecedented salt metathesis between a variety of BF4− salts and a series of organoboronic acids yielding the corresponding organotrifluoroborates. We identified conditions for fast and efficient fluoridation (<1 h) with minimal workup. Fundamentally, this work discloses the proclivity of BF4− to exchange fluoride atoms with organoboronates, highlighting the lability of BF4−. 相似文献
40.
Dr. Óscar Gutiérrez‐Sanz Dr. Paolo Natale Dr. Ileana Márquez Dr. Marta C. Marques Sonia Zacarias Dr. Marcos Pita Dr. Inês A. C. Pereira Dr. Iván López‐Montero Dr. Antonio L. De Lacey Dr. Marisela Vélez 《Angewandte Chemie (International ed. in English)》2016,55(21):6216-6220
ATP, the molecule used by living organisms to supply energy to many different metabolic processes, is synthesized mostly by the ATPase synthase using a proton or sodium gradient generated across a lipid membrane. We present evidence that a modified electrode surface integrating a NiFeSe hydrogenase and a F1F0‐ATPase in a lipid membrane can couple the electrochemical oxidation of H2 to the synthesis of ATP. This electrode‐assisted conversion of H2 gas into ATP could serve to generate this biochemical fuel locally when required in biomedical devices or enzymatic synthesis of valuable products. 相似文献