Influence of the Experimental System and Optimization of the Selectivity for the Electrocarboxylation of Chloroacetonitrile to Cyanoacetic Acid

Abstract

The electrocarboxylation of chloroacetonitrile (ClACN) to cyanoacetic acid in undivided cells equipped with sacrificial anodes was investigated 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 faradaic yields higher than 90% were obtained by working under anhydrous conditions with low halide concentrations and at more negative potentials. It was found that the instantaneous selectivity in the carboxylate compound depends mainly on the [CO 2 ]/[ClACN] ratio at high substrate concentration and is close to 100% for low ClACN concentration. These results were consistent with the previsions of a semiempirical model based on the assumption that under adopted experimental conditions the selectivity of the process is mainly determined by the competition between two very fast reactions: the carboxylation and a father-son reaction between the electrogenerated anion and the substrate. The effect of the nature of the solvent and of the concentration of proton donor species was further investigated.

Electrochemical synthesis of coenzymes Q n by oxidation of tetramethoxy precursors

“…Attempts to scale up electrochemical organic syntheses resulted in some cases in drastic decreases of both yields and faradic efficiencies as compared to experiments performed in bench-scale systems under similar operative conditions [4,19]. Hence, in order to test the role of the experimental system on the electrosyntheses of coenzymes Q 0 and Q 10 , some amperostatic electrolyses were performed in a continuous batch re-circulation cell (system II) with an initial substrate concentration of 10 mM.…”

“…Although the electrochemical reaction usually is only one step in a complex sequence, it has often the key-role of generating the activated intermediate. Hence, in the last years industrial and academic groups were involved several times in the investigation of new electrosynthetic routes for the preparation of fine and specialty chemicals [1][2][3][4]. Interestingly, many of these researches are not known because of secrecy requirements [1].…”

Electrocatalytic carboxylation of chloroacetonitrile at a silver cathode for the synthesis of cyanoacetic acid

“…The use of dangerous reagents such as cyanides makes this method of preparation an environmentally unfriendly process. For this reason, important research efforts have been carried out in the last 2 decades to find alternative methods using less dangerous reagents [2][3][4][5][6][7][8][9]. In particular, two electrochemical methods have recently been developed.…”

“…The best results, obtained with an experimental set-up using undivided cells equipped with sacrificial anodes, show Faradic yields lower than 30-40% [7]. The second is based on the cathodic reduction of NCCH 2 Cl at Hg [8] or carbon [8,9] cathodes in CO 2 -saturated aprotic solvents. This method gives good results both in terms of conversion and acid yields, but suffers from an inevitable employment of highly negative working potentials.…”

Electrocarboxylation of Benzyl Halides through Redox Catalysis on the Preparative Scale

“…Reduction of this species generally occurs at potentials much less negative than that of the parent organic halide due to the activation by the metal(ii) center producing an organometal, RTM I [Eq. (8)] or an organometal(0) anion [Eq. (9)], depending on the nature of the metal catalyst and of its ligands.…”