The Electrochemistry of the Triple Bond

Viertler, Hans; Pardini, Vera L.; Vargas, Reinaldo Romero

doi:10.1002/0470024771.ch10

Cited by 8 publications

(17 citation statements)

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“…The equations Polarograms of pNBD in aqueous acid (HCl 0.01 M) (not shown) contain three well-defined peaks and one shoulder. Two peaks that appear at Ϫ0.012 V (slightly overlapped with the peak of nitro reduction) and Ϫ0.474 V are attributed to the reduction of the arenediazonium ion to phenylhydrazine, Ar 9 NH 9 NH 2 (Scheme IIIA) in agreement with reported results for other arenediazonium salts [12,14,15,32]. The first peak of the diazo reduction is independent of pH up to pH ϭ 5 and, at higher pH, a peak potential shift of 38.4 mV per pH unit is observed up to pH 8 (this change in the peak potential/pH slope is probably related to the behavior of pNBD as a Lewis acid [6]).…”

Section: Preliminary Dpp and Dpv Experimentssupporting

confidence: 90%

“…Electrochemical reduction with metal electrodes such as Cu, Fe, Hg, and Ti has been used [14,15] to generate aryl radicals that act as initiators of polymerization [16]. When a arenediazonium ion acquires an electron [12, 14,15], it forms a diazenyl radical that yields an aryl radical and N 2 , as shown in Scheme II. Polarographic half-wave reduction potentials, E 1/2 , for a number of arenediazonium salts have been measured in a variety of solvents [17 -19].…”

Section: Introductionmentioning

confidence: 99%

“…The reduction of a number of 4-substituted benzenediazonium tetrafluoroborates has also been studied in aqueous solution [15] by employing a dropping mercury electrode (DME). The results have some confusing features.…”

Section: Introductionmentioning

confidence: 99%

“…A number of methods have been developed to monitor dediazoniations [26 -28]; however, little attention has been paid to the use of electrochemical methods [6,14,15,17,32]. Here we examined the dediazoniation of p-nitrobenzenediazonium tetrafluoroborate, pNBD, in aqueous solution by employing differential pulse polarography (DPP) at a DME and differential pulse voltammetry (DPV) on glassy carbon electrode (GCE) combined with a recently reported method [28] for using coupling reagents to quench the dediazoniation process at convenient times (Scheme IV).…”

Section: Introductionmentioning

confidence: 99%

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Electrochemical determination of rate constants and product yields for the spontaneous dediazoniation ofp-nitrobenzenediazonium tetrafluoroborate in acidic aqueous solution

Romero-Nieto

Bravo-Daz

Malvido-Hermelo

et al. 2000

Int. J. Chem. Kinet.

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We have examined the kinetics and mechanisms of the dediazoniation of p-nitrobenzenediazonium tetrafluoroborate in acidic aqueous solutions by employing differential pulse polarography (DPP) and differential pulse voltammetry (DPV) on a glassy carbon electrode combined with the use of a coupling reaction to quench unreacted p-nitrobenzenediazonium ion. These electrochemical techniques show an effective sensitivity and selectivity for detecting arenediazonium ions and arenedediazoniation products under the appropriate experimental conditions (pH, solvent, electrolyte), which allows simultaneous monitoring of the rates of arenediazonium ion loss and product formation and determination of product yields.

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Section: Preliminary Dpp and Dpv Experimentssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Electrochemical determination of rate constants and product yields for the spontaneous dediazoniation ofp-nitrobenzenediazonium tetrafluoroborate in acidic aqueous solution

Romero-Nieto

Bravo-Daz

Malvido-Hermelo

et al. 2000

Int. J. Chem. Kinet.

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“…À 0.05 V (Fig. 2, a) and À 1.2 V vs. Ag/AgCl (3m KCl), in agreement with [34] [49] [50]. Voltammograms (not shown) of HCl or buffered (Britton -Robinson) aq.…”

Section: Experimental Partsupporting

confidence: 75%

Kinetics and Mechanism of the Reaction between an Arenediazonium Ion and Methyl Gallate (=Methyl 3,4,5‐Trihydroxybenzoate) in Aqueous Solution: Evidence for Diazo Ether Formation through an O‐Coupling Reaction

Losada‐Barreiro

Sánchez-Paz

Bravo‐Díaz

2007

Helvetica Chimica Acta

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We have investigated the kinetics and mechanism of the reaction between 3-methylbenzenediazonium ions (3MBD) and methyl gallate (¼ methyl 3,4,5-trihydroxybenzoate; MG), in aqueous buffer solution by employing spectrophotometric (UV/VIS) and electrochemical (linear-sweep voltammetry, LSV) techniques and computational methods. Because the absorption band of MG overlaps that of 3MBD, the reaction was monitored spectrophotometrically by measuring the changes in absorbance with time due to product formation, and biphasic kinetic profiles, indicative of accumulation of an intermediate in the course of the reaction, were obtained. The formation of an intermediate was confirmed by LSV. The observed rate constants k obs for 3MBD disappearance were obtained by fitting the decrease in the peak current of the first reduction peak of 3MBD with time to the integrated firstorder equation. The variation of k obs with [MG] was determined at different pH values and follows a saturation kinetic pattern. Alternatively, at a fixed [MG], k obs values show an inverse dependence on [H þ ], suggesting that the reactive species is the anion and not the neutral form of MG. To discern which of the three OH groups of MG is the first one undergoing deprotonation, the geometries of the resulting anions were optimized by using B3LYP hybrid density functional theory (DFT) and a 6-31G(þ þ d,p) basis set. The deprotonation energies suggest that the OH group at the 4-position is first deprotonated. The kinetic results can be accommodated, therefore, by assuming two competitive mechanisms, the spontaneous D N þ A N decomposition involving 3MBD, and a mechanism involving an electrophilic attack at the O-atom at C(4) in a pre-equilibrium step, leading to the formation of a transient diazo ether of the type ArÀN¼NÀOÀR which further decomposes. All attempts to isolate and characterize the diazo ether failed.

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Kinetics and mechanism of the reaction between 4‐hexadecylbenzenediazonium ions and vitamin C in emulsions: further evidence of the formation of diazo ether intermediates in the course of the reaction

Pastoriza-Gallego¹,

Fernández-Alonso²,

Losada‐Barreiro³

et al. 2008

J of Physical Organic Chem

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The kinetics and mechanism of the reaction between hydrophobic 4-hexadecylarenediazonium ions, 16-ArN R 2 and vitamin C, VC, in a model emulsion prepared by mixing octane, acidic (HCl) water and the non-ionic surfactant hexaethyleneglycol monododecyl ether, C 12 E 6 , were investigated. Because emulsions are opaque, linear sweep voltammetry, LSV, was employed to monitor the reaction. Voltammograms of 16-ArN R 2 in emulsions show two reduction peaks as in aqueous systems. The half-life for the spontaneous decomposition of 16-ArN R 2 in the emulsion was estimated as t 1/2 ¼ 14.5 h at T ¼ 25 -C. Upon addition of VC to the system, the first reduction peak of 16-ArN R 2 disappears almost immediately and a new reduction peak is detected at E p ¼ S0.25 V. Electrochemical titration of 16-ArN R 2 shows that the new peak corresponds to the formation of a 1:1 adduct. The i P (E p ¼ S0.25 V) values can be linearly correlated with [16-ArN R 2 ] and the observed rate constants, k obs , were determined by fitting the (i p , t) data to the integrated first order equation. The variation of k obs with [VC] follows a saturation kinetics profile, consistent with the formation of an intermediate in a pre-equilibrium step. All the evidence is consistent with a reaction mechanism comprising two competitive pathways, the spontaneous D N R A N mechanism and the unimolecular decomposition of a transient diazo ether (DE) formed in a pre-equilibrium step. The data allowed estimations of the interfacial rate constant for the reaction between 16-ArN R 2 and VC S but did not allow the determination of the equilibrium constant for the DE formation.

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The Electrochemistry of the Triple Bond

Cited by 8 publications

References 0 publications

Electrochemical determination of rate constants and product yields for the spontaneous dediazoniation ofp-nitrobenzenediazonium tetrafluoroborate in acidic aqueous solution

Electrochemical determination of rate constants and product yields for the spontaneous dediazoniation ofp-nitrobenzenediazonium tetrafluoroborate in acidic aqueous solution

Kinetics and Mechanism of the Reaction between an Arenediazonium Ion and Methyl Gallate (=Methyl 3,4,5‐Trihydroxybenzoate) in Aqueous Solution: Evidence for Diazo Ether Formation through an O‐Coupling Reaction

Kinetics and mechanism of the reaction between 4‐hexadecylbenzenediazonium ions and vitamin C in emulsions: further evidence of the formation of diazo ether intermediates in the course of the reaction

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