共查询到20条相似文献,搜索用时 15 毫秒
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S. S. Ivanchev A. I. Yurzhenko A. F. Lukovnikov Yu. N. Gak S. M. Kvasha 《Theoretical and Experimental Chemistry》1971,4(6):501-505
ESR studies are reported for the peroxides derived from butyric, caproic, caprylic, lauric, and stearic acids. In every case, a six-component soectrum is observed, which is transformed to the spectrum of the peroxy radical in the presence of oxygen, so the spectrum is assigned to alkyl radicals formed by rupture of the peroxide bond and decarboxylation of the alkoxy radical. The rate constants and activation energies are deduced for the decay of the radicals. The activity is inversely related to chain length. Buildup curves under UV are examined, since these are dependent on chain length and light intensity. 相似文献
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A stable symmetric diacyl peroxide, m-chlorobenzoyl peroxide (mCBPO), and an asymmetric diacyl peroxide, chloroacetyl m-chlorobenzoyl peroxide (CAMCBPO), were synthesized from m-chloroperbenzoic acid. Both peroxides oxidized phenols selectively at the ortho position predominantly. CAMCBPO gave para-oxidized compounds as minor products from some phenols. The improvement of the yield of ortho-oxidation of phenols with mCBPO was also reported. 相似文献
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测定了过氧化月桂酰(1),过氧化辛酰(2),过氧化己酰(3)和过氧化3,5,5-三甲基己酰(4)在热分解过程中生成的羧基转化产物[RC(O)OC(O)OR,R=正十一烷基(5),正庚基(6),正戊基(7),2,4,4-三甲基戊基(8)]的含。在同样条件小,4生成的羧基转化产物比1,2和3的多。羧基转化反应受溶剂极性和粘度的影响,但温度的影响较小。转化产物的分解受体系中相应脂肪酸的催化。直接光照可生成少量转化产物,二苯酮光敏化不产生羧基转化产物,文中对反应机理进行了讨论。 相似文献
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[reaction: see text] Photolysis at 254 nm of neat (no solvent) unsymmetrical diacyl peroxides derived from cyclopropane carboxylic acids and l-aspartic acid generates protected beta-cyclopropylalanines in reasonable yields. Orthogonally protected 3-(trans-2-aminocyclopropyl)alanine (21), a key constituent of the antitumor agent belactosin A, as well as protected hypoglycin A (26), a causative agent of Jamaican vomiting sickness, is synthesized by this approach with coupling of the intermediate substituted cyclopropyl radicals proceeding predominantly with retention of configuration (dr >or= 95:5). 相似文献
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Curium hydrides were prepared by reaction of curium-248 metal with hydrogen and characterized by X-ray powder diffraction. Several of the syntheses resulted in a hexagonal compound with average lattice parameters of a0 = 0.3769(8) nm and c0 = 0.6732(12) nm. These products are considered to be CmH3?δ by analogy with the behavior of lanthanide-hydrogen and lighter actinide-hydrogen systems. Face-centered cubic products with an average lattice parameter of a0 = 0.5322(4) nm were obtained from other curium hydride preparations. This parameter is slightly smaller than that reported previously for cubic curium dihydride, CmH2+x (B. M. Bansal and D. Damien, Inorg. Nucl. Chem. Lett., 6, 603, 1970). The present results established a continuation of typical heavy trivalent lanthanide-like behavior of the transuranium actinide-hydrogen systems through curium. 相似文献
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In the presence of aerosil the thermal decomposition of the polymeric peroxide of sebacic acid is enhanced proportionally to the filler weight fraction in the reaction system. This is attributed to the interaction of peroxide groups with acidic groups on the aerosil surface and their decomposition according to a nonradical mechanism unlike the homolytic radical decomposition in solution.
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Massod A. Khan J. C. Bhatt B. M. Fung Kenneth M. Nicholas Ellen Wachtel 《Liquid crystals》2013,40(1):285-290
Abstract The crystal and molecular structure of 1,l ′-bis(4′-pentyloxybiphenyl)ferrocene dicarboxylate ester (1) has been determined by X-ray diffraction at 295 and 160K. The molecule is found to exist at both temperatures in an extended S geometry. The carboxyl groups are essentially coplanar with the cyclopentadienyl rings but almost perpendicular to the attached phenyl ring. Low angle X-ray diffraction of three diesters in the smectic phases were also studied. The results were not very definitive because of the lack of thermal stability for the monotropic phase behaviour. Nevertheless, the layer spacing of about 47 A for one of the compounds at 409K is consistent with the extended S shape conformation. 相似文献
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N. A. Turovskii S. Yu. Tselinskii Yu. E. Shapiro A. R. Kalyuskii 《Theoretical and Experimental Chemistry》1993,28(4):251-253
Intermolecular and ion-molecule interactions of benzoyl peroxide with tetraethylammonium chloride in an acetonitrile medium have been investigated by means of NMR. The types of association of the diacyl peroxide with ammonium chloride have been modeled by means of the MNDO method. The state of the peroxide molecule in the associate has been analyzed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 4, pp. 320–323, July–August, 1992. 相似文献
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In hexamethylphosphoric triamide (HMPA), four representative diacyl peroxides, namely, benzoyl peroxide (1), Cyclopropylformyl peroxide (2), lauroyl peroxide (3) and trifluoroacetyl peroxide (4), all decompose at rates much higher than those expected from their unimolecular thermal decomposition, and the corresponding carboxylic acids are formed in high yields (74–97%). Furthermore, several radical colligation products formed from HMPA molecules can be identified. Evidently, the initial step in the reaction between a diacyl peroxide and the “solvent” HMPA involves an electron transfer with the latter acting as the donor. 相似文献
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Single-crystal and polycrystalline urea samples were compressed to 12 GPa in a diamond-anvil cell. Raman-scattering measurements indicate a sequence of four structural phases occurring over this pressure range at room temperature. The transitions to the high-pressure phases take place at pressures near 0.5 GPa (phase I --> II), 5.0 GPa (II --> III), and 8.0 GPa (III --> IV). Lattice parameters in phase I (tetragonal, with 2 molecules per unit cell, space group P42(1)m (D3(2d))) and phase II (orthorhombic, 4 molecules per unit cell, space group P2(1)2(1)2(1) (D2(4))) were determined using angle-dispersive X-ray diffraction experiments. For phases III and IV, the combined Raman and diffraction data indicate that the unit cells are likely orthorhombic with four molecules per unit cell. Spatially resolved Raman measurements on single-crystal samples in phases III and IV reveal the coexistence of two domains with distinct spectral features. Physical origins of the spatial domains in phases III and IV are examined and discussed. 相似文献
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Samoilov's interstitial model for liquid water is considered. It is shown that geometrically different frameworks and different positions of cavity molecules lead to comparable degrees of agreement with the experimental radial distribution function. The meaning and the limits of these agreements are discussed. 相似文献
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Ivan Wlassics Vito Tortelli Marco Sala Donato Montrone 《Journal of fluorine chemistry》2003,121(1):65-74
This paper deals with the synthesis of perfluoropolyether (PFPE) (poly)diacyl peroxides with mean EWs ranging from 500 to 4000 g eq.−1 via H2O2 and base from the corresponding PFPE diacyl halides, their decomposition (thermal and hydrolytic) and the synthesis of the corresponding di-halides by the reaction with elemental halides. A great advantage of this novel synthesis over other synthetic approaches is the ease in obtaining polyperoxides containing up to at least two diacyl peroxide groups/chain. This property confers to these peroxides a greater thermal stability. The synthesis of PFPE diacyl peroxides and its dependence on contact times of reagents, solvent, reaction temperature and reagent concentrations will be presented and discussed. Data concerning the thermal and hydrolytic decomposition of these PFPE diacyl peroxides as well as the dependence of their homolytic decomposition kinetics on EW will also be presented and discussed. Interestingly, we have discovered that these PFPE (poly)diacyl peroxides could in turn be easily available precursors of the corresponding α-ω-iodides or bromides. 相似文献
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X-ray diffraction studies of platinum-alumina catalysts in a high-temperature chamber have revealed that for the catalysts obtained by the reduction of preactivated samples, no complete reduction of platinum takes place.
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S. V. Gardionov N. P. Shapkin M. I. Balanov V. V. Vasilieva V. I. Razov V. O. Trukhin 《Journal of Structural Chemistry》2016,57(3):507-511
X-ray diffractometry and positron annihilation life-time spectroscopy are applied to study the structural features of polymetallophenylsiloxane (PMOS) samples with the Si/M ratio corresponding to the metal valence state, namely, interplanar spacings (d001), coherentscattering region (CSR) sizes, cross-section areas of polymer chains (s) calculated by the Miller-Boyer method, and the degree of amorphousness (β). It is demonstrated that the direct proportional dependence between the logarithm of the interplanar spacing d001 and the logarithm of the cross-section area s is observed for PMOSs. This is an inverse dependence relative to changes in the crystal chemical ion radius. The extraction of the iron ion from polyferrophenylsiloxane leads to a sharp decrease in the interplanar spacing, which turns out to be less than d001 in polyphenylsiloxanes, and also CSR increases due to a decrease in the diameter of the polymer chain. The positron annihilation life-time spectroscopy data show the observed direct dependence of the annihilation intensity (I3), the annihilation rate (K3), the degree of amorphousness on the PMOS cross-section area. 相似文献