Mechanism of electrohydrodimerization of chalcone on mercury from aqueous solutions containing strong surfactants

Moncelli, Maria Rosa; Nucci, Lamberto; Mariani, Palma; Guidelli, Rolando

doi:10.1016/0022-0728(84)80176-x

Cited by 13 publications

(9 citation statements)

References 18 publications

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“…In the pH regions 6.3-7.5 and 9.0-10.1, the cathodic peak potential is independent of the concentration of buffer components, indicating that imidazole and boric acid do not react with intermediates of process II. At pH 8.00 and 8.51 up to 5 V s -~, good linear dependences between E~ and the logarithm of the boric acid concentration were found, with respective slopes of 21 and 13 mV per dec, as expected if boric acid acts as proton donor in the pH interval 8.0-8.5, such as reported for other a,l~-unsaturated ketones (22,24,26). The addition of LiC1 (up to 1.0M) to solutions of pH > 9 does not cause any variation of the slope of E~ vs. pH plots up to 10 V s -L, this excluding the possibility of ion-pair or complex formation between intermediates and Li § cation.…”

Section: A~era~e Value (-+2 Mv) a Average Value (-+ 2 MV Per Dec)supporting

confidence: 79%

Electrohydrodimerization of α,β‐Unsaturated Alicyclic and Aliphatic Ketones in Hydroethanolic Solutions on a Mercury Electrode: I . Reduction of 2‐Cyclopenten‐1‐One

Bastida

Brillas

Costa

1991

J. Electrochem. Soc.

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Electrohydrodimerization (EHD) of 2‐cyclopenten‐1‐one in buffered hydroethanolic solutions containing 50% (v/v) ethanol over the pH range 3.5–12.5 on mercury has been studied by polarography, cyclic voltammetry, and controlled‐potential electrolysis. A one‐electron reduction process is always found, the electroactive species being either its protonated form below pH 6.0 or its unprotonated form above pH 6.3. The diketone (1,1′‐bicyclopentyl)‐3,3′‐dione is obtained as reaction product in all tested media. Voltammetric data allow the proposition that the protonated form is reduced in a one‐electron step to give the corresponding neutral radical, which subsequently couples to yield the final diketone. For the unprotonated form, however, different EHD mechanisms can be established depending on the solution pH. All these pathways are initiated by generation of the radical anion via a one‐electron reduction step. In the pH region 6.3–7.5, the final diketone is formed by dimerization of the neutral radical obtained by protonation of the radical anion with H+ ion. In the pH zone 8.0–11.0, the same hydrodimer is generated via coupling of the radical anion with the neutral radical, followed by protonation of the resulting dimer anion. Under such conditions, voltammetric results indicate that at pH 8.0–8.5, the proton donor is either boric acid of the buffer or H+ ion, whereas at pH 9.0–11.0 it is only the H+ ion. Above pH 11.0 the radical anion couples to form a dimer dianion, which is further protonated by water to give the final diketone. The rate‐determining step of each EHD reaction depends on the voltammetric conditions employed.

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Section: A~era~e Value (-+2 Mv) a Average Value (-+ 2 MV Per Dec)supporting

confidence: 79%

Electrohydrodimerization of α,β‐Unsaturated Alicyclic and Aliphatic Ketones in Hydroethanolic Solutions on a Mercury Electrode: I . Reduction of 2‐Cyclopenten‐1‐One

Bastida

Brillas

Costa

1991

J. Electrochem. Soc.

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“…The current us. potential characteristic for this mechanism is reported in ref (4),. where the Koutecky-HanuS-Mairanovskii equation21* 22 for a reversible electron transfer followed by a coupling step was modified to include a preceding protonation in quasi-equilibrium.…”

mentioning

confidence: 81%

Mechanism of electrohydrodimerization of cyclohex-2-en-1-one on mercury from aqueous solutions. Part 1.—Results obtained in the absence of surfactants

Duarte¹,

Malanga²,

Nucci³

et al. 1988

J. Chem. Soc., Faraday Trans. 1

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The diffusion-controlled one-electron wave (wave I) due to cyclohex-2-en-1one (R) electroreduction on mercury from aqueous solutions in the range 2.5 < pH < 4 is shown to be consistent with the following mechanism : R + HA+ RH+ +A-where HA is a proton donor and the rate-determining coupling step (1 c), denoted by rds, proceeds in the adsorbed state. Double-potential-step chronocoulometric measurements indicate that R adsorption lies below the limits of sensitivity of the method, whereas R2H2 adsorption is appreciable at all potentials positive to -1.4 V us. SCE. The limiting current of wave I in the range 4 < pH < 6 is controlled by the protonation step (1 b), which is shown to proceed both heterogeneously and homogeneously. The contribution of the various proton donors, including adsorbed water, is pointed out. The diffusion-controlled one-electron wave (wave 11), which develops 4-2

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“…It is a pleasure to emphasize here the importance of the contribution of Prof. Rolando Guidelli and his coworkers to the understanding of the mechanism of activated olefin electrodimerization under the very conditions where the Baizer-Monsanto reaction is carried out. We indeed learned much from their systematic study of the role of surfactants when the reaction is carried out in aqueous conditions, as it is on the industrial scale [25][26][27][28][29][30][31][32][33]. The first mechanistic investigations of the electrodimerization of activated olefins in non-aqueous media, where interfacial effects are minimized, pointed to the occurrence of the same radical-radical coupling mechanism as with the carbonyl compounds.…”

Section: Introductionmentioning

confidence: 98%

Dimerization of electrochemically generated ion radicals: mechanisms and reactivity factors

Costentin

Savéant

2004

Journal of Electroanalytical Chemistry

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Mechanism of electrohydrodimerization of chalcone on mercury from aqueous solutions containing strong surfactants

Cited by 13 publications

References 18 publications

Electrohydrodimerization of α,β‐Unsaturated Alicyclic and Aliphatic Ketones in Hydroethanolic Solutions on a Mercury Electrode: I . Reduction of 2‐Cyclopenten‐1‐One

Electrohydrodimerization of α,β‐Unsaturated Alicyclic and Aliphatic Ketones in Hydroethanolic Solutions on a Mercury Electrode: I . Reduction of 2‐Cyclopenten‐1‐One

Mechanism of electrohydrodimerization of cyclohex-2-en-1-one on mercury from aqueous solutions. Part 1.—Results obtained in the absence of surfactants

Dimerization of electrochemically generated ion radicals: mechanisms and reactivity factors

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