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Cyanide Anion (cyanide + anion)
Selected AbstractsTheoretical and Experimental Study of the Regioselectivity of Michael AdditionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2004David C. Chatfield Abstract Nucleophilic attack at an ,,,-unsaturated carbonyl moiety usually results in conjugate addition at the ,-carbon atom (1,4 or Michael addition) or, occasionally, in addition at the carbonyl carbon atom (1,2 addition). Recently, however, addition at the ,-carbon atom has been observed when strongly electron-withdrawing groups are positioned at the carbon atom , relative to the carbonyl group [e.g., methyl 3,3-bis(trifluoromethyl)propenoate (8) and ethyl 3-(2,4-dinitrophenyl)propenoate (24)]. We have performed theoretical calculations [HF/6,31+G(d) and B3LYP//HF/6,31+G(d)] for the addition of cyanide anion to model ,,,-unsaturated carbonyl compounds to determine trends in the regioselectivity with respect to properties of the substituents. The difference between the reaction barriers for ,- vs. ,-addition decreases as the strength of electron-withdrawing groups increases until, for sufficiently strong electron-withdrawing groups, ,-addition becomes favored. The calculations are in agreement with the experimental results. We show that the regioselectivity can be predicted from partial atomic charges and properties of the frontier orbitals of the reactants. We also report new experimental evidence of ,-addition to polysubstituted cinnamates and cinnamaldehydes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] A Highly Sensitive Hybrid Colorimetric and Fluorometric Molecular Probe for Cyanide Sensing Based on a Subphthalocyanine Dye,ADVANCED FUNCTIONAL MATERIALS, Issue 9 2006E. Palomares Abstract A highly sensitive, selective colorimetric and fluorometric molecular probe based on a subphthalocyanine dye has been developed for cyanide-anion determination in aqueous solution. It has also been shown that a carboxysubphthalocyanine derivative can be covalently anchored to transparent mesoporous nanocrystalline high-surface-area metal oxide films to detect low concentrations of cyanide anion in pure water with no interference from other anionic or cationic species. [source] New Insight into the Mode of Action of Nickel Superoxide Dismutase by Investigating Metallopeptide Substrate ModelsCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2009Daniel Tietze M. Abstract For the first time, the existence of a substrate adduct of a nickel superoxide dismutase (NiSOD) model, based on the first nine residues from the N terminus of the active form of Streptomyces coelicolor NiSOD, has been proven and the adduct has been isolated. This adduct is based on the cyanide anion (CN,), as a substrate analogue of the superoxide anion (O2.,), and the nickel metallopeptide H-HCDLPCGVY-NH2 -Ni. Spectroscopic studies, including IR, UV/Vis, and liquid- and solid-state NMR spectroscopy, show a single nickel-bound cyanide anion, which is embedded in the metallopeptide structure. This complex sheds new light on the question of whether the mode of action of the NiSOD enzyme is an inner- or outer-sphere mechanism. Whereas discussion was previously biased in favor of an outer-sphere electron-transfer mechanism due to the fact that binding of cyanide or azide moieties to the nickel active site had never been observed, our results are a clear indication in favor of the inner-sphere electron-transfer mechanism for the disproportionation of the O2., ion, whereby the substrate is attached to the Ni atom in the active site of the NiSOD. [source] | ||||||||||