On Radical Anions in Elucidation of Mechanisms of Organic Reactions.

Lund, Hakon; Daasbjerg, Kim; Lund, Torben; Occhailini, D.; Pedersen, Steen Uttrup; Niinistö, Lauri; Styring, Stenbjörn; Tommos, Cecilia; Warncke, Kurt; Wood, Bryan R.

doi:10.3891/acta.chem.scand.51-0135

Cited by 60 publications

(39 citation statements)

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“…The competition between reactions of Eq. 10 and 11 depends on the difference between the standard reduction potentials of the radical R " and catalyst, 46 When ⌬E is large, as it is in our case, reduction of the radical outruns the coupling reaction and the overall process becomes a 2e Ϫ reduction of the halide to the corresponding carbanion. However, in all MCB-catalyzed experiments, we found that at the end significant deactivation of the ester had occurred during electrolysis.…”

Section: Resultsmentioning

confidence: 79%

Electrochemical Synthesis of Cyanoacetic Acid from Chloroacetonitrile and Carbon Dioxide

Isse

Gennaro

2002

J. Electrochem. Soc.

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The electrochemical carboxylation of chloroacetonitrile was investigated in dimethylformamide ͑DMF͒ and acetonitrile ͑MeCN͒ by cyclic voltammetry and controlled-potential electrolysis. Both direct electroreduction and mediated reduction of the halide in CO 2 -saturated solvents were used to achieve the electrocarboxylation process. Also the effects of cathode material and cell type ͑divided or undivided with dissolving anode͒ were examined. In DMF the electrolyses performed in the divided cell resulted in low to moderate yields of NCCH 2 CO 2 H ͑25-45%͒, independent of the electrode material and catalyst type. The process is remarkably more efficient in MeCN, in which acid yields of ca. 60% were obtained under similar conditions. Very good results were obtained in both solvents when an undivided cell with aluminum sacrificial anode was used. In this case, the acid yield increased to 73 and 93% in DMF and MeCN, respectively.Cyanoacetic acid and its derivatives such as alkyl cyanoacetates are employed as starting materials in many industrial processes. 1 The current method of production of this acid makes use of the reaction between chloroacetic acid and alkali metal cyanides. 1 Alternative methods of synthesis, involving less dangerous reagents, have been described in a number of patents. [2][3][4][5] In particular, carboxylation of acetonitrile with CO 2 has attracted some attention. Kawamata et al. 4 and Tyssee 5 described the preparation of cyanoacetic acid by carboxylation of acetonitrile. This method requires deprotonation of CH 3 CN to NCCH 2 Ϫ , which is then trapped by CO 2 . To generate NCCH 2 Ϫ , Kawamata et al. 4 used alkali phenolates in DMF whereas Tyssee 5 used an electrochemical method. More recently, attempts to carboxylate acetonitrile by employing 1,3-diphenylurea or diphenylcarbodiimide in the presence of alkalimetal carbonates and CO 2 have given unsuccessful results. 6,7 Anodic oxidation of cyanoethanol 8 or some ␤-cyanoethyl ethers 9 at a Pt or PbO 2 electrode in 1.6 M H 2 SO 4 has been reported to give cyanoacetic acid as one of the principal oxidation products. Although good yields of acid were obtained under certain conditions, significant amounts of HCN were always formed as a side product. The electrochemical reduction of organic halides in CO 2 -saturated aprotic solvents has been extensively investigated as a synthetic route to carboxylic acids. 10-21 High faradaic and chemical yields were obtained when electrolyses were performed in undivided cells with sacrificial Al or Mg anodes. 10-12 Also catalytic systems, mainly based on transition-metal complexes, were employed with good results in either divided or undivided cells. 13-21 Two major reaction routes were identified in such catalytic processes. With some nickel, 13,15 palladium, 16 and cobalt 17-19 complexes, electrocarboxylation proceeds through involvement of metal-centered intermediates. In other systems the process is initiated by interaction between the reduced form of the mediator and RX whereby free radicals R " are formed...

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Section: Resultsmentioning

confidence: 79%

Electrochemical Synthesis of Cyanoacetic Acid from Chloroacetonitrile and Carbon Dioxide

Isse

Gennaro

2002

J. Electrochem. Soc.

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“…For example, it was reported 136 In general, it is evident 61 that a SET process is governed by the difference in the oxidation potential of a nucleophile and the reduction potential of a partner reactant. The difference between these two potentials, E = E ox − E red , was used by Okubo and coworkers 138 -142 to estimate the relative efficiency of SET (the so-called ' E approach').…”

Section: Concluding Remarks: Electrochemical Data In the Elucidamentioning

confidence: 99%

Electrochemistry of Organomagnesium Compounds

Jaworski

2009

Patai's Chemistry of Functional Groups

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Introduction Electrochemical Synthesis of Organomagnesium Compounds Conductivity of Solutions of Organomagnesium Compounds Anodic Oxidation of Organomagnesium Compounds Cathodic Reduction of Organomagnesium Compounds Organomagnesium Compounds as Intermediates in Electrode Reactions Concluding Remarks: Electrochemical Data in the Elucidation of Reactivity of G rignard Reagents

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“…radical anions and cations; and carbenes [1][2][3][4][5][6][7][8], or, in a broader sense, to the problem of electron transfer [2,3]. The redox properties of intermediates to a large extent define the direction and efficiency of electrode processes, including those in organic electrochemistry [3 − 12].…”

Section: Introductionmentioning

confidence: 99%

“…Detailed information about redox properties of intermediates happens to be critically important not only for the characterization of the electron transfer [2,3] but also for a successful realization of electrosynthetic processes of practical value [6][7][8][9][10][11][12]31], in particular, electrocatalytic [6,7,12] (in the first place, mediated oxidation and reduction of stable compounds), predictions of the direction of radical reactions (dimerization, cross-coupling, radical abstraction of H atoms and some others from a substrate, disproportionation), and so on (see for example [4-14, 20, 21, 31]). In particular, detailed investigation of redox properties of intermediates has already made it possible to explain why a number of reactions expected a priori do not occur in reality, for example, the cross-coupling of radicals during the photoreduction of benzophenone by 2propanol [6][7][8] or the dimerization of radical β -hydroxyethyl to 1,4-butanediol in media from acid to weakly alkaline [32].…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic and kinetic characteristics of intermediates of electrode reactions: Determination by direct and combined electrochemical methods

2005

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The potentialities of electrochemical and combined methods for the determination of thermodynamic characteristics and kinetic parameters of intermediates are analyzed. The electrochemical methods include polarography, versions of voltammetry, and chronopotentiometry. The combined methods combine nonelectrochemical (or indirect) generation of intermediates with electrochemical methods of their subsequent investigation: photomodulation voltammetry, method of polarography of pulsed-radiolysis products, method of indirect electrolysis, electrochemiluminescence, and a group of laser photoemission methods. Theoretical foundations and basic advantages and disadvantages of the laser photoemission methods (the measurement of photocurrents in potentiostatic conditions-method of time resolved voltammograms obtained under chopped illumination and the measurement of the kinetics of variations in the potential of an electrode after illuminating it by a pulsed laser-in coulostatic conditions) are described in detail. The potentialities of the laser photoemission methods for the determination of thermodynamic (standard potentials E 0 of redox pairs / R -, standard adsorption free energies) and kinetic (values of rate constants W 0 at an equilibrium potential, bulk lifetime of radicals and products of their reduction R -) characteristics of intermediates are demonstrated by studying a trifluoromethyl radical.

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On Radical Anions in Elucidation of Mechanisms of Organic Reactions.

Cited by 60 publications

References 0 publications

Electrochemical Synthesis of Cyanoacetic Acid from Chloroacetonitrile and Carbon Dioxide

Electrochemical Synthesis of Cyanoacetic Acid from Chloroacetonitrile and Carbon Dioxide

Electrochemistry of Organomagnesium Compounds

Thermodynamic and kinetic characteristics of intermediates of electrode reactions: Determination by direct and combined electrochemical methods

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