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61.
The ab initio energies, nuclear and electron repulsions and charge distributions have been calculated using moderately large basis sets as a function of the RC N angle (R NH2, NF2 or PF2). The optimum RC N angles were calculated to be 178.9°, 176.6°, and 175° for NH2CN, NF2CN, and PF2CN, respectively. A rationalization of the differing bends is presented in terms of nuclear-nuclear and electron-electron repulsions. 相似文献
62.
Christian Roussel Alexandru T. Balaban Ulf Berg Michel Chanon Roger Gallo Gerd Klatte Joseph A. Memiaghe Jacques Metzger Daniela Oniciu Johanna Pierrot-Sanders 《Tetrahedron》1983,39(24):4209-4219
The effect of the shape of a methyl group on reactivity, which cannot be accounted for by considering a methyl group as a spherical substituent with the appropriate van der Waals radius, was considered in kinetics of alkylalion of substituted pyridines and barriers to rotation and ground state conformations of an isopropyl group attached to a planar framework. The perturbation of a methyl group by an o-methyl group is accounted for by a unique conformational explanation which involves the polyhedral shape of the methyl group. 相似文献
63.
Ti(III)-induced free-radical decomposition of a phenyldiazonium salt, followed by phenyl radical iodine-atom abstraction from alkyl iodides, leads to a one-pot selective alkyl radical addition to the C-atom of imines generated in situ under aqueous acidic conditions. [reaction: see text] 相似文献
64.
Simon J. Garden Marilza B. Corrêa Angelo C. Pinto James L. Wardell John N. Low Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(4):o234-o238
In ethyl N‐[2‐(hydroxyacetyl)phenyl]carbamate, C11H13NO4, all of the non‐H atoms lie on a mirror plane in the space group Pnma; the molecules are linked into simple chains by a single C—H⋯O hydrogen bond. The molecules of ethyl N‐[2‐(hydroxyacetyl)‐4‐iodophenyl]carbamate, C11H12INO4, are linked into sheets by a combination of O—H⋯I and C—H⋯O hydrogen bonds and a dipolar I⋯O contact. Ethyl N‐[2‐(hydroxyacetyl)‐4‐methylphenyl]carbamate, C12H15NO4, crystallizes with Z′ = 2 in the space group P; pairs of molecules are weakly linked by an O—H⋯O hydrogen bond and these aggregates are linked into chains by two independent aromatic π–π stacking interactions. 相似文献
65.
Angelo Gilio 《International Journal of Approximate Reasoning》2012,53(3):413-434
In this paper we first recall some notions and results on the coherence-based probabilistic treatment of uncertainty. Then, we deepen some probabilistic aspects in nonmonotonic reasoning, by generalizing OR, CM, and Cut rules. We also illustrate the degradation of these inference rules when the number of premises increases. Finally, we show that the lower bounds obtained when applying OR and Quasi-Conjunction inference rules coincide, respectively, with Hamacher and Lukasiewicz t-norms; the upper bounds in both rules coincide with Hamacher t-conorm. 相似文献
66.
67.
Camila L. de Camargo Letícia S. ShiromaGabriela F. Giordano Angelo L. GobbiLuis C.S. Vieira Renato S. Lima 《Analytica chimica acta》2016
This paper addresses an important breakthrough in the deployment of ultra-high adhesion strength microfluidic technologies to provide turbulence at harsh flow rate conditions. This paper is only, to our knowledge, the second reporting on the generation of high flow rate-assisted turbulence in microchannels. This flow solves a crucial bottleneck in microfluidics: the generation of high throughput homogeneous mixings. We focused on the fabrication of bulky polydimethylsiloxane (PDMS) microchips (without any interfaces) rather than the laborious surface modifications that were employed in the first reporting about turbulence-assisted microfluidics. The fabrication is cleanroom-free, simple, low-cost, fast, solventless, and bondless requiring only a laboratory oven. More specifically, our method relies on the shaping of a nylon scaffold, cure of PDMS with embedded nylon, and removal of this scaffold. The scaffold was obtained by manually wrapping nylon threads. The withdrawing out of the scaffold was completed in few seconds using only a plier. Such microchannels endured flow rates of up to 60.0 mL min−1 with a strikingly low elastic deformation. The importance in producing turbulence into microscale channels was successfully shown in liquid-liquid extractions. The great energy dissipation rate relative to the turbulence created high throughput and efficient extractions in microfluidics for the first time. The residence time was only 0.01 s at 25.0 mL min−1 (total flow rate of the immiscible phases). In addition, the partition coefficient determined in a single run was similar to that obtained by the conventional batch shake-flask method that was realized in triplicate. 相似文献
68.
69.
Gabriella Ieronimo Alessandro Mondelli Francesco Tibiletti Angelo Maspero Giovanni Palmisano Simona Galli Stefano Tollari Norberto Masciocchi Kenneth M. Nicholas Silvia Tagliapietra Giancarlo Cravotto Andrea Penoni 《Tetrahedron》2013
The thermal reaction between nitrosoarenes and alkynes under alkylating conditions produces N-alkoxyindoles as the major products in moderate to good yields and excellent regioselectivity. Various electrophiles are used affording different N–O-protected hydroxyindoles in a multi-component fashion. Privileged acetylenic substrates used in reactions with substituted nitrosoarenes are arylalkynes or propiolates. Potentially bioactive compounds and other classes of highly functionalizable indole products were prepared. Reactions between o-carbomethoxy-nitrosoarenes and arylacetylenes provided tricyclic compounds containing an acylaziridine indoline skeleton. 相似文献
70.
Giancarlo De Santis Luigi Fabbrizzi Maurizio Licchelli Piersandro Pallavicini Angelo Perotti Antonio Poggi 《Supramolecular chemistry》2013,25(2):115-125
Abstract The new ferrocene-containing water-soluble ligands 1 and 2 were synthesized and their protonation and complexation properties toward NiII and CuII studied as a function of pH, by means of potentiometric titration experiments. Electrochemical measurements were performed in aqueous solution on pure 1 and 2 and in the presence of NiII and CuII cations, in the pH range 2–12, allowing us to determine the redox potential values relative to the ferrocene oxidation in the free ligands and in their NiII and CuII complexes. 1 and 2 behave as redox switchable ligands, the former enhancing, the latter decreasing its binding ability upon oxidation of the appended ferrocene function. Besides, the CuII complex of ligand 1 and the NiII complex of ligand 2 behave as two-centre two-electron redox systems, the complexed metal cation being subject to further oxidation to MIII. 相似文献