Electrocatalytic carboxylation of chloroacetonitrile at a silver cathode for the synthesis of cyanoacetic acid
Abstract The electrocatalytic carboxylation of chloroacetonitrile to cyanoacetic acid performed at silver cathodes was investigated both theoretically and experimentally. Silver exhibits powerful electrocatalytic activities towards the reduction of chloroacetonitrile. In CO 2 -saturated CH 3 CN, reduction of NCCH 2 Cl occurs at potentials that are about 0.7 V more positive than those observed at glassy carbon and gives cyanoacetic acid in good yields. Theoretical considerations on the effect of operative parameters on the performances of the process were confirmed by electrocarboxylation experiments performed in undivided cells equipped with sacrificial anodes both in a bench-scale electroc…
The influence of aluminium cations on electrocarboxylation processes in undivided cells with Al sacrificial anodes
Abstract The influence of Al cations on the electrochemical carboxylation of acenaphthylene ( 1 ), benzophenone ( 2 ), 6-methoxy-2-acetonaphthone ( 3 ), and benzyl chloride ( 4 ) has been investigated in dimethylformamide at a glassy carbon cathode. The Al 3+ ions were either added at the beginning of the experiment or were released from the anode during electrocarboxylation. It has been found that when Al cations are added to the reaction medium, they strongly influence the reduction process, in most cases leading to a complete change of the mechanism. For example, in the case of 1 , the radical anion ( 1 − ) formed upon 1e − reduction rapidly reacts with Al 3+ to give an Al(III) adduct, w…
Atom transfer radical polymerization with different halides (F, Cl, Br, and I): Is the process "living" in the presence of fluorinated initiators?
Atom transfer radical polymerization (ATRP) is often used for grafting from fluorinated polymers. Nevertheless, the possibility to initiate an ATRP from a C-F functionality and the activity of the catalysts in the presence of fluoride anions are essentially unexplored. Therefore, we investigated the thermodynamics and kinetics of C-F bond activation by ATRP catalysts and compared it with other halide systems. The ATRP equilibrium constant was estimated to be small for the reaction between [CuITPMA]+ and benzyl fluoride (TPMA = tris(2-pyridylmethyl)- amine). However, [CuITPMA] + could react with the more active initiator diethyl fluoromalonate (DEFM). With DEFM as initiator and CuIBr/TPMA as…
Electrochemical reduction and carboxylation of halobenzophenones
Abstract The electrochemical reduction of a series of halogenated benzophenones XC6H4COC6H4Y (1) was studied in aprotic solvents, in the absence and presence of CO2, by cyclic voltammetry (CV) and controlled-potential electrolysis. The mechanism of electroreduction in dimethylformamide (DMF) has been investigated in some detail. Most of the compounds undergo reductive carbonhalogen bond cleavage in the time window of CV. The radical anions derived from difluorobenzophenones (X=Y=4-F; X=2-F, Y=4-F) as well as from the 3-chloro derivative are quite stable with a cleavage rate constant (kc) of the order of 10−2 s−1 or less. With 4-chloro-, 2-chloro-, 4,4′-dichloro- and 2,4′-dichorobenzophen…
Smooth crack-free targets for nuclear applications produced by molecular plating
The production process of smooth and crack-free targets by means of constant current electrolysis in organic media, commonly known as molecular plating, was optimized. Using a Nd salt, i.e., [Nd(NO3)(3)center dot 6H(2)O], as model electrolyte several constant current density electrolysis experiments were carried out to investigate the effects of different parameters, namely the plating solvent (isopropanol and isobutanol mixed together, pyridine, and N,N-dimethylformamide), the electrolyte concentration (0.11, 0.22, 0.44 mM), the applied current density (0.17, 0.3, 0.7, and 1.3 mA/cm(2)), and the surface roughness of the deposition substrates (12 and 24 nm). Different environments (air and …
Electrocarboxylation of aromatic ketones: Influence of operative parameters on the competition between ketyl and ring carboxylation
Abstract The purpose of this work is to investigate the effect of operational parameters on the competition between the formation of the target 2-hydroxy-2-arylpropanoic acid and ring carboxylation in the electrocarboxylation of aromatic ketones. For the investigated ketones, this competition has been found to be dramatically influenced by different parameters such as the water content and the ratio between the carbon dioxide and the ketone concentrations (q = [CO2]/[ketone]). In particular, the target carboxylic acid formation can be favoured with respect to ring carboxylation by operating at high q ratios or by addition of small amounts of H2O to the reaction medium. An increase of the wa…
Electrocarboxylation of benzyl chlorides at silver cathode at the preparative scale level
Abstract The electrocarboxylation of benzyl chlorides to the corresponding carboxylic acids performed at silver cathodes was investigated both theoretically and experimentally in order to find the influence of the operative parameters on the selectivity and on the Faradic efficiency of the process. Theoretical considerations were confirmed by the electrocarboxylation of 1-phenyl-1-chloroethane performed in undivided cells equipped with sacrificial anodes both in a bench-scale electrochemical batch reactor and in a continuous batch recirculation reaction system equipped with a parallel plate electrochemical cell. Selectivity and Faradic yields higher than 80% and 70%, respectively, were obta…
Elucidation of constant current density molecular plating
Abstract The production of thin layers by means of constant current or constant voltage electrolysis in organic media is commonly known as molecular plating. Despite the fact that this method has been applied for decades and is known to be among the most efficient ones for obtaining quantitative deposition, a full elucidation of the molecular plating is still lacking. In order to get a general understanding of the process and hence set the basis for further improvements of the method, constant current density electrolysis experiments were carried out in a mixture of isopropanol and isobutanol containing millimolar amounts of HNO 3 together with [Nd(NO 3 ) 3 ·6H 2 O] used as a model electrol…