Mercury Pool Cathode Research Articles

An electrochemical route to poly(p-phenylenevinylene) polymers (PPVs) and copolymers via cathodically generated quinodimethanes: preparative and structural aspects

An electrochemical route to poly(p-phenylenevinylenes)(PPVs) is described which involves cathodic cleavage of bis(dibromomethyl)arenes at a mercury pool cathode. Insoluble and organosoly PPVs are obtained in good yields and are characterised as regular and linear. Copolymers are obtained by co-electrolysis of different bis(dibromomethyl)arenes. The method is versatile and much functionality is tolerated. The polymers can be made conducting by doping with BF3 or SO3. The effect of substituents on conductivity correlates, roughly but significantly, with Hammett σ-values. Poly(p-phenylenevinylene), the parent PPV, forms conducting blends with poly(vinyl alcohol).

Identification of different products obtained by electrochemical and photochemical reduction of the herbicide metamitron

The electrochemical reduction of the herbicide Metamitron (4-amino-4,5-dihydro-3-methyl-6-phenyl-1,2,4-triazin-5-one) has been carried out at different pHs using a mercury pool cathode. The final product of these reductions depends both on the electrolysis potential and on the pH. All processes are irreversible and the reductions of the CN and the NNH 2 (pH > 3) or NNH + 3 bond (pH < 3) are inferred. An aqueous solution of Metamitron is also degraded by sunlight leading to 4,5-dihydro-3-methyl-6-phenyl-1,2,4-triazin-5-one (deaminometamitron). This reaction can be monitored polarographically.

Electrochemical reductions of 2-furoyl chloride, furil and 2-furaldehyde at mercury cathodes in acetonitrile

Cyclic voltammograms for the reduction of 2-furoyl chloride at a hanging mercury drop electrode in acetonitrile containing tetraethylammonium perchlorate exhibit six cathodic waves. Electrolytic cleavage of the carbon- chlorine bond is responsible for the first wave. Controlled-potential electrolyses of 2-furoyl chloride generate the tetramer 1,2-di(2-furyl)ethene-1,2-diol di(2-furoate) as the major product, whereas small amounts of 2- furaldehyde are obtained when a 10-fold excess of glacial acetic acid is initially present in the system. A cyclic voltammogram for reduction of furil at a hanging mercury drop in acetonitrile containing tetraethylammonium perchlorate shows a pair of reversible cathodic waves. Electrolyses of furil at a mercury pool cathode yield 2-furoic acid, 1,2-di(2-furyl)-2-hydroxy-3-cyanopropanone and 1,2-di(2-furyl)ethanone; when furil is electrolyzed in the presence of an excess of 2-furoyl chloride or glacial acetic acid, the principal product is the aforementioned tetramer or furoin, respectively. One irreversible wave is observed when cyclic voltammograms are recorded for the reduction of 2-furaldehyde at a hanging mercury drop in acetonitrile containing tetraethylammonium perchlorate. Bulk electrolyses of 2-furaldehyde produce 3-(2-furyl)acrylonitrile, hydrofuroin, 3-(2-furyl)propionitrile and 3-(2-furyl)glutaronitrile, together with the hydrodimer (2,3-di(2-furyl)-1,4-dicyanobutane) and possibly oligomers derived from the coreduction of 3-(2-furyl)acrylonitrile.

Electrochemical conversion of α-nitrobenzylic compounds into the corresponding oximes—Part 2. Macroscale electrolyses

Electroreduction of α-nitrobenzylic compounds, performed in aqueous acetic buffer (65%) and ethanol (35%) leads to a mixture of oxime and hydroxylamine; the latter can be oxidized into oxime, via the corresponding nitroso. Differents strategies have been developed in order to improve the conversion yield into oxime: controlled potential reduction in a batch cell at a mercury pool cathode, followed either by chemical iodine oxidation or by controlled potential oxidation; galvanostatic electrolyses carried out in a flow cell fitted either with two consecutive porous electrodes of opposite polarities or with only a porous cathode, the flowing out solution being oxidized with iodine. The last method gives the best results and conversion yields of 90% are reached.

The electrohydrogenation of 2-iodonitrobenzene at mercury and Raney metal electrodes in aqueous methanol

The electrohydrogenation of 2-iodonitrobenzene at mercury and Raney metal electrodes (R-Ni, R-Co and D-Cu) was studied in aqueous methanolic solutions. Four different media were used: a basic KOH medium (pH > 13), a neutral acetate buffered medium (pH 7) and two media containing a pyridine buffer (pH 3 and pH 10). Cyclic voltammetric reductions were carried out at mercury, bright nickel and bright copper cathodes. The product distribution of preparative-scale electrolyses at a mercury pool cathode was compared with that of electrohydrogenation at Raney metal electrodes and of catalytic hydrogenation (open-circuit experiments) at Raney metals. Electrohydrogenation at R-Co and D-Cu electrodes gave 2-iodoaniline with high selectivity ( ⩾ 94%). The results are discussed in the light of the various mechanistic pathways.

The multi-step reversible reduction of 1,4,5,8-naphthalene tetracarboxylic acid dianhydride: An electrochemical study

Voltammetric experiments on 1,4,5,8-naphthalene tetracarboxylic acid dianhydride ( I) (A) at a glassy carbon electrode (GC) in dry dimethylformamide +0.1 M Et 4NClO 4 are presented. The one-electron reduction of A produces anion radical A −: A+e − ⇄ A −. Subsequent electron transfers (A − +e − ⇄ A 2− and A −2+e − ⇄ A 3−) give rise to persistent dianion A 2− and radical trianion A 3−, with standard potentials E 1 0 = −0.28 V, E 2 0 = −0.69 V and E 3 0 = -2.42 V (SCE), respectively. The above data have been used to assign the (relative) electron-acceptor property of I, in terms of electron affinity (EA). and the equilibrium constants for some redox reactions involving A, A −, A 2− and A 3−. In the presence of excess RX = t-BuBr, the redox couple A −/A 2− ( E 2 0) is replaced by a more positive one with E 2 0 = − 0.55 V. Reversible interaction of A 2− with 2 mol of RX/mol A 2− is indicated. Nothing similar happens with RX = 1-bromoadamantane. The results of preparative electrolyses of A in the presence of t-BuBr using a mercury pool cathode are also reported. R'= t-Bu-radical-derived products, i.e. HgR 2 and dimers, were found, but only if A 2− was produced at rather negative potentials, albeit where RX is not reduced directly. Minor products of preparative electrolyses of A were anhydride-lactone ( II) and a red product to which structure III was assigned. UV-visible spectra of A 2− are also reported.

Electrochemical ring-contraction of fused [1,3,4]thiadiazinium salts: preparation of fused pyrazole derivatives

The electroreduction of several fused [1,3,4]-thiadiazinium salts on mercury pool cathode in an aprotic medium has been studied. In preparative experiments using dimethylformamide 0.2 M in lithium perchlorate as the electrolyte, the [1,3,4]-thiadiazinium salts 1- 3 formed a mixture of the corresponding fused pyrazoles and ketimines. On the basis of results of preparative electrolyses (products and reaction potentials) and cyclic voltammograms a posible mechanism is proposed.

Electrochemical reductive alkylation of (benzophenone)Cr(CO) 3 and (benzophenone)[Cr(CO) 3] 2

The electrochemical reduction of (benzophenone)Cr(CO) 3 and (benzophenone)[Cr(CO) 3] 2 in hthe presence of a series of alkyl chlorides which are more difficult to reduce, has been carried out in N,N-dimethylformamide on a mercury pool cathode. When methyl chloride and p-cyanobenzyl chloride are used as alkylating agents, complexed monoalkylated ethers are exclusively obtained as substitution products, in yields ranging from 36 to 54%. Complexed alkylated alcohols aer isolated as the major products when (benzophenone)Cr(CO) 3 is reduced in the presence of benzyl-chloride and its 2,3,5-trimethyl derivative, in 48 and 44% yields, respectively. These last results suggest the intermediate formation of a charge transfer complex between the aromatic ring of the electrophile and the complexed ketone.

Hydrodimerisation electroassistee par des sels metalliques, en milieu aprotique, de la phenyl-1 dimethyl-4,4 pentene-1, one-3

The electrochemical reduction of 1-phenyl 4,4-dimethyl pentene 3-one can be achieved in an aprotic medium (DMF) on a mercury pool cathode, in the presence of metallic chlorides (Li +, Cr 2+, Fe 2+, Mn 2+, Co 2+, Zn 2+, Ni 2+). There is selective hydrodimerization, with very high yields, either into ε racemic diketone or cyclopentanic ketol with total lack of polymerization. An acid—basic interaction between ketone and metallic cation, acting as Lewis acid, is postulated.

Electrochemical synthesis of pyrido[1,2-a]pyrimidine derivatives. II. Electrochemical reduction of 2,6-dimethyl-3-ethyl-4-oxo-4H-pyrido[1,2-a]pyrimidine in aqueous media

The electrochemical reduction of 2,6-dimethyl-3-ethyl-4-oxo-4H-pyrido[l,2-a]pyrimidine (base and HCl salt) was investigated by polarography and controlled potential electrolysis in aqueous buffered solutions at different pH values on a dropping mercury electrode and a mercury pool cathode. Controlled potential electrolyses performed in methanolic borate buffer solution (pH=9, 10) at the first polarographic wave (1.45 V vs SCE) gave a stable C-8-coupled hydrodimer (III) in a one-electron process with a product yield of 52%. Reduction performed in alkaline methanolic solution (pH=13.4), at the second polarographic wave (− 1.86 V vs SCE) showed a dihydromonomer (IV) formation with a product yield of 87%, in a two-electron process.

Electroreduction of (benzophenone)tricarbonylchromium and (fluorenone)tricarbonylchromium in the presence of electrophiles

(Benzophenone)Cr(CO) 3 ( 2) and (fluorenone)Cr(CO) 3 ( 3) are reduced at a mercury pool cathode in aprotic media, in the presence of an electrophile which is more difficult to reduce. The results are compared with those which are obtained with the corresponding parent ketone. In the presence of 1,3-dibromopropane, a complexed olefinic alcohol 7a is the major isolated compound when 2 is the substrate, whereas a complexed spiro ether 8b is obtained with 3 as substrate. The electroreduction of 3 in acetonitrile in the presence of an equivalent amount of 4-chlorobutyryl chloride gives mainly the diacylated complex 10a. The unexpected formation of a nitrile complex 12a is also observed, which indicates an interaction between an intermediate species and acetonitrile. Complex 12a is obtained in low yield by the electroreduction of 3 in the presence of 3-bromopropionitrile. Under these conditions the major compound is (fluorenol)Cr(CO) 3.

One-step electrosynthesis of tetrahydrofuran and tetrahydropyran derivatives

The one-step electrosynthesis of tetrahydrofuran and tetrahydropyran derivatives was achieved by electrogenerating in N,N-dimethylformamide and at a mercury pool cathode, radical-anions of benzophenone or fluorenone in the presence of an equivalent of 1,3-dibromopropane 1 or 1,4-dibromobutane 2. In all electrolyses, a competition between ring alkylations and O- and C-alkylations of the keto group is observed. In the case of fluorenone, the spiroethers were isolated as the main compounds. Their yields after purification were respectively 41 and 50% in the presence of 1 and 2. For benzophenone, the yields of the cyclic ethers were low, due mainly to the competitive formation of bridged compounds; the yields of tetrahydrofuran and tetrahydropyran derivatives were respectively 10 and 23%.

Electroreduction of selenium at a mercury pool cathode in aprotic media Application to the electrosynthesis of dibenzyl selenide and diselenide

Electroreduction of selenium at a mercury pool cathode in aprotic media Application to the electrosynthesis of dibenzyl selenide and diselenide

Electroreduction of selenium at a mercury pool cathode in aprotic media: Application to the electrosynthesis of dibenzyl selenide and diselenide

Electroreduction of selenium at a mercury pool cathode in aprotic media: Application to the electrosynthesis of dibenzyl selenide and diselenide

Hydrodimerisation electrochimique de cetones aromatiques encombrees en milieu aprotique et en presence de chlorure de chrome

The electrochemical reduction of hindered aromatic ketones which are difficult to reduce alone, can be achieved in an aprotic medium (DMF) on a mercury pool cathode, in presence of Cr(III) chloride, at the reduction potential or the Cr(II)/Cr(0) system, but at a less negative potential than that of the ketone itself. There is selective hydrodimerisation into an α-glycol, with total lack of polymerisation. With dissymetric ketones, the dl-diastereoisomers of the diols are produced. The effect of chromium is due either to the reduction of a Cr-ketone complex or to the reduction of the ketone by a film of colloidal chromium on the electrode surface.

Réduction électrochimique de cétones aromatiques encombrées en milieu aprotique et en présence de chlorure de manganèse

The electrochemical reduction of hindered aromatic ketones which are difficult to reduce can be achieved in an aprotic medium (DMF) on a mercury pool cathode, in presence of Mn(II) chloride, at the reduction potential of the Mn(II)/Mn(0) system, but less negative than that of the ketone itself. There is selective hydrodimerization into an α-glycol, with total lack of polymerization. With dissymmetric ketones, the dl diastereoisomers of the diols are produced preferentially. The effect of manganese is due either to the reduction of a Mn(I) or Mn(0) – ketone complex or to the reduction of the ketone by a film of colloidal manganese on the electrode surface.

Stereochemical Studies of the Electrolytic Reactions of Organic Compounds. Part 18. Comparative Study of Hydrogenation on Metal-black Cathodes and Catalysts

Abstract Stereoselective hydrogenation on metal-black cathodes and catalysts, which were prepared by electrode-position under the same conditions, was comparatively investigated. Stereoisomeric ratios of alcohols formed from the ketones on the Pd- and Pt-black cathodes seemed to be almost equal to those on the corresponding metal-black catalysts, while the yields were quite different between the cathodic and catalytic hydrogenations. On the other hand, results of the hydrogenation of the acetylenes on the cathodes were also different, in not only the yield but also the isomeric ratio, from those on the catalysts. In addition to stereoselectivity, relative hydrogenation rates between cis- and trans-olefins were compared in both the cathodic and catalytic hydrogenations. It was also found that a mercury pool cathode gave quite different stereochemical results in the hydrogenation of the unsaturated compounds from those obtained with either the metal-black cathodes or the catalysts.

Sequential Electrochemical Reduction, Solvent Partition, and Automated Thiol Colorimetry for Urinary Captopril and its Disulfides

Analysis of urinary captopril was necessary for dosage form bioavailability and dose titration studies. The necessity for long-term storage of samples prior to analysis and the presence of an oxidation-prone thiol of captopril required development of an acid-chelate stabilization method for urinary captopril. An electrochemical reduction released disulfide-conjugated captopril for thiol colorimetry. Of several rugged reduction cells evaluated, one with a porous glass disk separating the anode and the mercury pool cathode was preferred. Methylene chloride partitions from acidified salt-saturated urines, before and after reduction, allowed the measurement of free and disulfide-conjugated captopril. The drug partitioned into the solvent, whereas the aqueous phase retained acid protonated, amino group-bearing thiols like cysteine. Subsequent solvent evaporation volatilized other potential colorimetric interferences. An automated thiol colorimetry of 25 samples/hr was developed for analysis of the aqueous reconstitutes. Results were confirmed by a subsequently developed HPLC method with electrochemical detection.

Reductive Alkylation of 2-Methyl 1-1 ,4-Naphthaquinone (Menadione) at Mercury Pool Cathode

Reductive Alkylation of 2-Methyl 1-1 ,4-Naphthaquinone (Menadione) at Mercury Pool Cathode

On the nature of a pre-step observed in the electroreduction of cobalt(II)-thiocyanate complexes

Using the method of stationary electrode voltammetry with hanging mercury drop and glassy carbon electrodes, the electroreduction of Co(II)-thiocyanate complexes occurring at smaller cathodic potentials than the formal potential of the Co(II)/Co(Hg) couple was studied. This process results in the formation of CoS and CN − ions, and occurs only on electrode surfaces modified by the presence of CoS with an admixture of metallic cobalt. The maximum efficiency of this reaction, calculated with respect to the charge passed through the cell, was found to be 75%, on the basis of macroelectrolysis carried out at a mercury pool cathode. The influence of various factors on the electroreduction of SCN − was also studied.