Showing papers by "Armando Gennaro published in 2008"
TL;DR: It is concluded that a hypothetical outer-sphere electron transfer (OSET) in ATRP should occur via concerted dissociative electron transfer rather than a two-step process with radical anion intermediates, implying that the ISET mechanism is preferred.
Abstract: High-level ab initio molecular orbital calculations are used to study the thermodynamics and electrochemistry relevant to the mechanism of atom transfer radical polymerization (ATRP). Homolytic bond dissociation energies (BDEs) and standard reduction potentials (SRPs) are reported for a series of alkyl halides (R−X; R = CH2CN, CH(CH3)CN, C(CH3)2CN, CH2COOC2H5, CH(CH3)COOCH3, C(CH3)2COOCH3, C(CH3)2COOC2H5, CH2Ph, CH(CH3)Ph, CH(CH3)Cl, CH(CH3)OCOCH3, CH(Ph)COOCH3, SO2Ph, Ph; X = Cl, Br, I) both in the gas phase and in two common organic solvents, acetonitrile and dimethylformamide. The SRPs of the corresponding alkyl radicals, R•, are also examined. The computational results are in a very good agreement with the experimental data. For all alkyl halides examined, it is found that, in the solution phase, one-electron reduction results in the fragmentation of the R−X bond to the corresponding alkyl radical and halide anion; hence it may be concluded that a hypothetical outer-sphere electron transfer (OSET) in ...
248 citations
TL;DR: The reductive cleavage of a series of organic chlorides was investigated at Ag, Cu, Pd and glassy carbon electrodes in CH(3)CN + 0.1 M (C(2)H(5))(4)NClO(4), offering a more favourable route possibly through the formation of strongly adsorbed activated complexes.
Abstract: The reductive cleavage of a series of organic chlorides, including chloroaromatics, benzyl chlorides, activated chloroalkanes and polychloromethanes, was investigated at Ag, Cu, Pd and glassy carbon (GC) electrodes in CH3CN + 0.1 M (C2H5)4NClO4. The silver cathode was either a 2-mm diameter disc, fabricated from Ag wire, or nanoclusters of average diameter d = 304 nm, prepared by electrodeposition on GC. Ag, Cu and Pd electrodes have shown remarkable electrocatalytic properties for the reduction of several compounds. The peak potentials recorded at these electrodes, for example, at υ = 0.1 V s−1 are positively shifted by 0.3–0.8 V with respect to the reduction potentials measured at a non catalytic electrode such as GC. Electrocatalysis is strictly related to the concerted nature of the dissociative electron transfer to the carbon–chlorine bond. No catalysis is observed when the dissociative electron transfer to RCl occurs according to a stepwise mechanism involving the intermediate formation of a radical anion. The catalytic surfaces affect the reaction scheme, offering a more favourable route possibly through the formation of strongly adsorbed activated complexes.
133 citations
TL;DR: In this paper, the influence of the operative parameters on the selectivity and on the Faradic efficiency of the benzyl chlorides to the corresponding carboxylic acids performed at silver cathodes was investigated both theoretically and experimentally in order to find the influence on selectivity, which was confirmed by the electrocarboxylation of 1-phenyl-1-chloroethane performed in undivided cells equipped with sacrificial anodes.
65 citations
TL;DR: In this article, the electrocatalytic carboxylation of chloroacetonitrile to cyanoacetic acid performed at silver cathodes was investigated both theoretically and experimentally.
44 citations
TL;DR: In this article, a stepwise approach is proposed to evaluate catalytic active surface areas relative to a non-catalytic reference one, particularly focusing on the modulating effects of the bulkiness and reactivity of the probe molecules.
Abstract: Appropriately dealing with real surface area evaluation in organic electrocatalysis implies working mostly in organic media, and, above all, adopting molecular probes. Their selection is not straightforward, implying preliminary knowledge of the structural and mechanistic effects possibly modulating the probe molecule’s perspective of the electrode surface. Taking the electrocatalytic reduction of organic bromides on polycrystalline silver as a model process, we propose a stepwise approach to the evaluation of catalytic active surface areas, relative to a non-catalytic reference one, particularly focusing on the modulating effects of the bulkiness and reactivity of the probe molecules.
3 citations