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

Abstract

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.

Formation and Reactivity of 3-Diazopyridinium Cations and Influence on Their Reductive Electrografting on Glassy Carbon

“…However, the diazotization reaction is very fast in our experimental conditions, and as a consequence, no clear evidence for the formation of these products was found either by NMR or by high-resolution mass spectrometry. Second, the presence of chloride ions in solution (HCl media) should enable the formation of chloro compounds as competitive side-products of the hydroxyl compounds. ,, The presence of a reaction byproduct, such as 3-chloropyridine (8.8, 8.6, 8.5, and 7.9 ppm, see Figure S3), was observed in a small amount (∼5%) by 1 H NMR (within the limits of 1 H NMR 300 MHz). This can be explained by a low selectivity of 3-diazopyridium cations toward nucleophiles like Cl – compared with water .…”

“…For example, the formation of diazopyridinium cations has been investigated by Kalatzis and Papadoloupos . The reactivity of phenyldiazonium salts has been investigated by different techniques such as chemical trapping, HPLC, , and electrochemical experiments in aqueous media, UV spectroscopy in aqueous and in organic media, measurements of evolved nitrogen, and NMR spectroscopy in organic media …”

Spontaneous modification of glassy carbon surface with anthraquinone from the solutions of its diazonium derivative: An oxygen reduction study

“…The mechanism of arenediazonium reactions in solution has been a matter of controversy since it can vary drastically with experimental conditions and compound structure changing the reaction pathway and the dediazoniation product distribution [63][64][65][66][67][68][69][70].…”

“…Solvents of low nucleophilicity favour the S N 1 mechanism while those of high nucleophilicity favour a free radical mechanism. Their rate depends on the aromatic ring substituents and experimental conditions such as pH or solvent [63][64][65][66][67][68][69][70].…”

Kinetics and mechanism of the reaction of an arenediazonium ion with hydrophilic aminocarboxylic acids in aqueous buffered solution

“…In addition to 4NBD ions, their homolytic and heterolytic dediazoniation products and derivatized azo dyes possess electroactive groups thus allowing simultaneous determination of product yields and rate constants electrochemically by monitoring either the loss or the formation of a variety of products. 12,30,31 The choice of LSV as working tool was also decided on view of the results of preliminary UV-vis experiments (not shown) carried out by monitoring the absorbance at l ¼ 370 nm due to product formation, revealing a complex biphasic kinetic behavior with absorbances increasing with time up to a maximum after which a slow decrease was detected.…”