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961.
Cameron TS Lemaire MT Passmore J Rawson JM Shuvaev KV Thompson LK 《Inorganic chemistry》2005,44(8):2576-2578
Reduction of the radical-cation [*NSSNC-CNSNS][AsF(6)] with ferrocene affords the novel biradical *NSNSC-CNSSN* containing both 1,2,3,5- and 1,3,2,4-isomeric dithiadiazolyl rings. Biradicals form centrosymmetric dimers with pi(*)-pi(*) interactions between different isomeric rings. Biradical *NSNSC-CNSSN* is diamagnetic in the solid state (C = 0.00035, TIP = 6.5 x 10(-)(5) emu/Oe.mol); however, an increase in paramagnetism was observed upon grinding (C = 0.003, TIP = 4.2 x 10(-)(4) emu/Oe.mol). 相似文献
962.
963.
964.
Correct proofs are given for Theorem 3 and the Propositions of §§5, 6 of [4]. For the latter, we must modify the principle
(S)″ in a technical way. We prove a weaker version of Theorem 2, where □ is replaced by the stronger hypothesis PΓN
1
b.
Partially supported by NSF grant MCS 8301042. 相似文献
965.
Stanley Fiorini 《Journal of Combinatorial Theory, Series B》1975,18(1):35-38
Vizing [Diskret. Analiz3 (1964), 25–30] has shown that if ? denotes the maximum valency of a simple graph, then its chromatic index is either ? or ? + 1. The object of this paper is to show that the chromatic index of an outerplanar graph G is ? if and only if G is not an odd circuit. 相似文献
966.
Tetsuro Oie Gilda H. Loew Stanley K. Burt Robert D. Macelroy 《Journal of computational chemistry》1983,4(4):449-460
As a model reaction for peptide and bond formation, the SN2 reactions between glycine and ammonia have been studied with and without amine catalysis: using ab initio molecular-orbital methods. For each of the catalyzed and uncatalyzed reactions, two reaction mechanisms have been examined: a two-step and a concerted mechanism. The stationary points of each reaction, including intermediate and transition states, have been identified and free energies calculated for all geometry-optimized reaction species to determine the thermodynamics and kinetics of the reaction. The calculations demonstrate that a second ammonia molecule catalyzes amide bond formation, and that the two-step mechanism is more favorable than the concerted one for the catalyzed reaction, while for the uncatalyzed reaction both mechanisms are competitive. 相似文献
967.
968.
Stanley D. Furrow 《国际化学动力学杂志》1979,11(2):131-145
The reaction\documentclass{article}\pagestyle{empty}\begin{document}$ CH\left({CH_3 } \right)\left({COOH} \right)_2 + I_2 \rightleftharpoons CI(CH_3)\left({COOH} \right)_2 + H^ + + I^ - $\end{document} was followed spectrophotometrically at 353 nm and 470 nm at 25°C under various conditions of pH and methylmalonic acid concentration. The equilibrium constant for the reaction is 0.11 ± 0.02. An iterative technique was used to integrate postulated rate equations. Agreement between experimental and calculated absorbance versus time curves was generally better than 0.005 A (approximately 5% of maximum) at both wavelengths for a mechanism where the rate-determining step is formation of an enolate (k = 1.63 Θ 10?4 ± 0.03 Θ 10?4 sec?1). The enolate may be rapidly transformed to the enol or enol carboxylate anion depending on the pH. All three forms are rapidly iodinated. The mechanism of general base catalysis is supported by rate increases proportional to base concentration in buffer solutions. The bases, acetate ion, chloracetate ion, sulfate ion, dichloracetate ion, and water, follow a Brønsted relationship with β = 0.7. 相似文献
969.
970.