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91.
Hong-Bo Ni 《Journal of fluorine chemistry》2006,127(3):426-432
The radical reactions of polyolefin and olefin copolymers (4-9), polydienes and diene coplymers (10-15), and polysiloxane (16) with “magic blue” reagent containing H-abstracting agent-bis{perfluoro-1-[1-(2-fluorosulfonyl)ethoxy]ethyl}nitroxide [FSO2CF2CF2OCF(CF3)]2N(O) (2)and spin trap-perfluoro-1-nitroso-[1-(2-fluoro-sulfonyl)ethoxy]ethane FSO2CF2CF2OCF(CF3)NO (3) were studied by EPR detection of the spin adducts of the corresponding polymeric radicals generated in the H-abstraction step to the spin trap 3, namely, the nitroxides FSO2CF2CF2OCF(CF3)N(O) (polymer-H) 17-29. EPR studies have provided information about the regio-selectivity of H-abstraction, the subsequent radical steps followed H-abstraction and grounded a possibility of employing “magic blue” reagent in polymer modification via H-abstraction-initiated grafting polymerization. 相似文献
92.
Raymond Turner 《Entropy (Basel, Switzerland)》2021,23(2)
Representation and abstraction are two of the fundamental concepts of computer science. Together they enable “high-level” programming: without abstraction programming would be tied to machine code; without a machine representation, it would be a pure mathematical exercise. Representation begins with an abstract structure and seeks to find a more concrete one. Abstraction does the reverse: it starts with concrete structures and abstracts away. While formal accounts of representation are easy to find, abstraction is a different matter. In this paper, we provide an analysis of data abstraction based upon some contemporary work in the philosophy of mathematics. The paper contains a mathematical account of how Frege’s approach to abstraction may be interpreted, modified, extended and imported into type theory. We argue that representation and abstraction, while mathematical siblings, are philosophically quite different. A case of special interest concerns the abstract/physical interface which houses both the physical representation of abstract structures and the abstraction of physical systems. 相似文献
93.
Hue Minh Thi Nguyen Asit K. Chandra Shaun A. Carl Minh Tho Nguyen 《Journal of Molecular Structure》2005,732(1-3):219-224
We have theoretically investigated the hydrogen abstraction reactions of ethynyl radical with simple hydrogen compounds, C2H+HX, using quantum chemical computations. Computations have been performed using the density functional theory with the recently proposed MPW1K functional and the 6-311++G(3df,2p) basis set. An analysis of the resulting energy barriers for hydrogen abstraction reactions has been carried out using the bond dissociation energy of the breaking X–H bond and DFT-based reactivity parameters to rationalize the reaction behavior. 相似文献
94.
The reaction of 1-fluorooctane (1) with an excess of lithium powder (4-10 equiv.) and DTBB (2-4 equiv.) in THP at 0°C for 5 min gives a solution of the corresponding 1-octyllithium (2), which reacts then with different electrophiles at 0°C (D2O, MeSiCl, ButCHO, Et2CO), or −78°C [ClCO2Me, (PhCH2S)2] or −40°C (CO2) to room temperature to give, after hydrolysis, the expected products (3). The same process applied to 2-fluorooctane gives mainly octane as reaction product, independently on the electrophile used, resulting from a proton abstraction by 2-lithiooctane formed from the reaction medium before addition of the electrophilic reagent. 相似文献
95.
The effect of the inclusion of the exact exchange into self-interaction corrected generalized gradient approximation density
functional theory (GGA-DFT) for the simplest hydrogen abstraction reaction, H + H2 → H3 → H2 + H, is presented using a triple-zeta augmented 6-311++G(d,3pd) basis set. The introduction of the self-interaction correction has a considerably larger effect on molecular geometry and
vibrational frequencies than the inclusion of the exact exchange. We investigate the influence of the self-interaction error
on the shape of the potential energy surface around the transition state of the hydrogen abstraction reaction. The decomposition
of the self-interaction error into correlation and exchange parts shows that the exchange self-interaction error is the main
component of the energy barrier error. The best agreements with the experimental barrier height were achieved by self-interaction
corrected B3LYP, B-LYP and B3PW functionals with errors of 1.5, 2.9 and 3.0 kcal/mol, respectively.
Received: 13 August 1997 / Accepted: 14 November 1997 相似文献
96.
Noboru Mataga 《中国化学会会志》1995,42(2):127-140
Results of our femtosecond-picosecond laser photolysis studies on photoinduced electron transfer phenomena in solutions including exciplex dynamics and its solvent dependences, energy gap dependences of photoinduced charge separation and charge recombination of various geminate ion pairs, mechanisms of chemical reactions via exciplexes and ion pairs, dynamics of photoinduced election transfer in hydrogen bonding complexes, dynamics and mechanisms of photoinduced electron transfer in fixed distance donor acceptor dyads and photosynthetic reaction center models, and mechanisms of electron ejection from solute fluorescent state in polar solutions are summarized and discussed. 相似文献
97.
98.
99.
Five hydrogen abstraction reactions, CH4 + R CH3 + HR have been studied usingab initio SCF and CI methods. R was successively chosen as H, CH3, NH2, OH and F. Geometries were fully optimized at SCF level and energies were computed at CI level for products, reactants and transition states. Quadratic hypersurfaces were fitted in the neighborhood of the most important points of the potential energy hypersurfaces and vibrational analysis were performed thereupon. Wigner's and Christov's approximations were used to obtain an idea of the importance of tunneling of H atoms through the reaction barrier, and this effect was shown to be non-negligible. Finally, rate constant calculation were carried out at different temperatures.Chercheur Qualifié au Fonds National Belge de la Recherche Scientifique. 相似文献
100.
I. A. Opeida A. G. Matvienko O. Z. Bakurova 《Theoretical and Experimental Chemistry》2006,42(1):22-25
The rate constants for the reaction of the TEMPO radical with fluorene, 2-cyanofluorene, and 9-cyanofluorene were determined
by ESR. A comparison was made of the reactivity of the hydrocarbons in reaction with the TEMPO radical and the peroxyl radical.
The quantum-chemical characteristics of the radicals and particles taking part in the reactions and also the characteristics
of the transition states in the reactions of the TEMPO radical and cumenylperoxyl radical with fluorene were obtained by the
PM3 method.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 1, pp. 19–22, January–February, 2006. 相似文献