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71.
72.
73.
Edgar Marquez Alexis Maldonado Felix Rosas Beatriz Ramirez Gabriel Chuchani 《Molecular physics》2014,112(3-4):462-473
The kinetics and mechanisms of thermal decomposition of phenyl acetate and p-tolyl acetate in the gas phase were studied by means of electronic structure calculations using density functional theory methods: B3LYP/6-31G(d,p), B3LYP/6-31++G(d,p), B3PW91/6-31G(d,p), B3PW91/6-31++G(d,p), MPW1PW91/6-31G(d,p), MPW1PW91/6-31++G(d,p), PBE/6-31G(d,p) and PBE/6-31++G(d,p). Two possible mechanisms have been considered: mechanism A is a stepwise process involving electrocyclic [1,5] hydrogen shift to eliminate ketene through concerted six-membered cyclic transition-state structure, followed by tautomerisation of cyclohexadienone or by 4-methyl cyclohexadienone intermediate to give the corresponding phenol. Mechanism B is a one-step concerted [1,3] hydrogen shift through a four-membered cyclic transition-state geometry, to produce ketene and phenol or p-cresol. Theoretical calculations showed reasonable agreement with experimental activation parameters when using the Perdew, Burke and Ernserhof (PBE)functional, through the stepwise [1,5] hydrogen-shift mechanism. For mechanism B, large deviation for the entropy of activation was observed. No experimental data were available for p-tolyl acetate; however, theoretical calculations showed similar results to phenyl acetate, thus supporting the stepwise mechanism for both phenyl acetate and p-tolyl acetate. 相似文献
74.
Klukovich HM Kean ZS Black Ramirez AL Lenhardt JM Lin J Hu X Craig SL 《Journal of the American Chemical Society》2012,134(23):9577-9580
Epoxidized polybutadiene and epoxidized polynorbornene were subjected to pulsed ultrasound in the presence of small molecules capable of being trapped by carbonyl ylides. When epoxidized polybutadiene was sonicated, there was no observable small molecule addition to the polymer. Concurrently, no appreciable isomerization (cis to trans epoxide) was observed, indicating that the epoxide rings along the backbone are not mechanically active under the experimental conditions employed. In contrast, when epoxidized polynorbornene was subjected to the same conditions, both addition of ylide trapping reagents and net isomerization of cis to trans epoxide were observed. The results demonstrate the mechanical activity of epoxides, show that mechanophore activity is determined not only by the functional group but also the polymer backbone in which it is embedded, and facilitate a characterization of the reactivity of the ring-opened dialkyl epoxide. 相似文献
75.
Jose Luis Castro Maria Rosa Lopez‐Ramirez Juan Francisco Arenas Juan Carlos Otero 《Journal of Raman spectroscopy : JRS》2012,43(7):857-862
The Surface‐enhanced Raman scattering of benzenesulfonamide and sulfanilamide adsorbed on silver sols was studied. On the basis of the noticeable shifts observed for wavenumbers of the νs(OSO), ν(CS), and ν(SN) vibrations with respect to the Raman spectra of the solids and the ionic solutions, we conclude that these molecules are adsorbed on silver nanoclusters at pH ≥ 7 with the aminosulfonyl groups partially deprotonated. The benzenesulfonamide links to the metal through the nitrogen atom of the corresponding azanion, while the sulfanilamide interacts in turn through the nitrogen atoms of the –NH2 and –SO2NH– groups in the para‐position. Additionally, it was found that the most enhanced surface‐enhanced Raman scattering bands, especially the 8a;νring mode, are related to the presence of the charge transfer mechanism. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
76.
Teodoro Cordova-Fraga Modesto Sosa Martha Alicia Hernandez-Gonzalez Jose Antonio Reyes-Aguilera Sergio Solorio Chystian Ramirez Evelia Bautista-Flores Guadalupe Reynaga Mario Avila-Rodriguez Jose Maria De la Roca-Chiapas 《Applied magnetic resonance》2012,42(2):161-167
Magnetic resonance imaging (MRI) of the gastrointestinal (GI) tract is still limited due to the lack of widely available oral
contrast agents (OCA). The availability of OCA for MRI of the GI tract is a necessity; different fruits might be implemented
as OCA in order to solve this need throughout the year. The objective of this study is to present an alternative fruit as
a clinical OCA for MRI of the GI tract, Achras sapota L. (common medlar). Both physical and chemical characterization of the medlar was performed. It was also tested in situ and
in vivo as an OCA for MRI of the GI tract. Results showed that this fruit had a diamagnetic behavior, although it has enough
iron, manganese and copper to contrast the GI tract in T
1- and T
2-weighted images. Thus we conclude that the medlar fruit has shown a potential as an OCA in GI evaluation by MRI, so it can
be considered as an alternative in complementation of natural OCA. 相似文献
77.
Ramirez AG Miller AR Gallion K San Miguel de Majors S Chalela P García Arámburo S 《Community genetics》2008,11(4):215-223
78.
E. I. Klimova M. Martinez Garcia T. Klimova L. Ruiz Ramirez J. M. Mendez Stivalet N. N. Meleshonkova 《Russian Chemical Bulletin》2000,49(3):514-519
3,5-Bis(ferrocenylmethylene)-1-methyl-4-methylenepiperidine, a diferrocenyltriene with a fixeds-cisoid conformation of the exocyclic double bonds, was synthesized. On heating, this compound cyclodimerizes according to
the [4+2]-cycloaddition scheme; it forms Diels-Alder adducts with azodicarboxylic and maleic acidN-phenylimides. The compound easily cyclodimerizes in the presence of acids by a proton cyclodimerization mechanism to give
a spiro cyclodimer. The triene also adds a 3,5-bis(ferrocenylmethylene)-1,4-dimethyl-1-azonia-4-cyclohexyl salt to the terminal
methylene group yielding linear and cyclic addition products.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 511–516, March, 2000. 相似文献
79.
Lee J. Silverberg Carlos Pacheco Debashish Sahu Peter Scholl Hany F. Sobhi Joshua T. Bachert Kaitlyn Bandholz Ryan V. Bendinsky Heather G. Bradley Baylee K. Colburn David J. Coyle Jonathon R. Dahl Megan Felty Ryan F. Fox Kyanna M. Gonzalez Jasra M. Islam Stacy E. Koperna Quentin J. Moyer Duncan J. Noble Melissa E. Ramirez Ziwei Yang 《Journal of heterocyclic chemistry》2020,57(4):1797-1805
A series of 11 novel 3-aryl-2-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-ones was prepared at room temperature by T3P-mediated cyclization of N-aryl-C-phenyl imines with thiosalicylic acid. This provides simple and ready access to N-aryl compounds in this family, which have been generally difficult to prepare. 相似文献
80.
Espinoza-Vergara Javier Pavez Jorge Gonzalez Evelyn Ramirez Cristián Páez Maritza Gulppi Miguel 《Journal of Solid State Electrochemistry》2019,23(12):3225-3229
Journal of Solid State Electrochemistry - Here we demonstrate that the metal ion excess after precipitating a sparingly soluble metal salt can be conveniently determined by a secondary... 相似文献