Dediazoniation of arenediazonium ions in homogeneous solution. Part VIII. Reaction kinetics and products in dimethyl sulfoxide

Abstract

p-Nitrobenzenediazonium tetrafluoroborate dissolved in dimethylsulfoxide (DMSO) at 50" forms p-nitrophenol in 88-90% yield. The phenolic oxygen atom originates exclusively from the oxygen atom of DMSO as demonstrated by the use of 180-labelled DMSO. The first-order rate of dediazoniation is the same under Nz as it is in the presence of air. The rate is little influcnccd by the addition of benzene or iodobenzenc. However, the products formed in the presence of thcsc additives are significantly different. UV. spectra and thc reactivity of diazonium salt solutions in DMSO when mixed with reagents in aqueous solution demonstrate that a relatively stable chargc-transfer complex is formed between the diazonium ion and DMSO. The product analyses and the kinetic and spectral results of dediazoniation in DMSO with and without additives are consistent with a mechanism in which the rate-limiting step is the formation of a 9-nitrophcnyl radical from the charge-transfer complex. 9-Nitrophenol and the products with benzene and iodobenzene are formed in subsequent fast competition steps. In the presence of small amounts of pyridine the dediazoniation is much faster and follows a different kinetic law. Pyridine effectively competes with DMSO in the reaction with diazonium ions.

On the mechanism of photocatalytic reactions with eosin Y

“…The energy of a photon at the edge of the visible spectrum (400 nm) is 3.1 eV so that such photons carry sufficient energy to heterolyze diazonium ions to give highly electrophilic aryl cations. Moreover, arenediazonium salts are known to form weak charge-transfer complexes with solvent molecules whose absorption tails into the visible range [ 30 ].…”

“…The absorption spectrum of a mixture of para -bromobenzenediazonium tetrafluoroborate ( p -BrC 6 H 4 N 2 BF 4 ) and bispinacolato diboron (B 2 pin 2 ) in acetonitrile shows a significant shoulder of a UV-absorption band tailing into the visible part of the spectrum ( Fig. 3 ) [ 30 ]. At the UV–vis edge (400 nm), the absorbance of the system is still more than 0.1 which translates into 21% of all light being absorbed at this wavelength.…”

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].…”

Mechanochemical borylation of aryldiazonium salts; merging light and ball milling

“…Under non-catalyzed LAG/irradiation conditions, charge-transfer complexes between 1a and appropriate organic solvents could be responsible for the fast generation of the aryl cations in the ball mill, leading to the direct formation of 3a [ 26 – 27 ]. This observation is in agreement with the findings by Jacobi von Wangelin et al, who described that upon irradiation of a solution of 1a in MeCN direct heterolytic cleavage of the aryldiazonium salt occurred [ 23 , 25 ].…”