Evidence for phenyl cation as an intermediated in reactions of benzenediazonium salts in solution

Effect of Ring Size on the Complexation and Decomposition of Benzenediazonium Ion in the Presence of Crown Ethers in 1,2-Dichloroethane and the Gas Phase

“…In accordance with earlier investigations by kinetic and spectroscopic measurements and product analyses by GC and/or GC-MS, 5, 6, 9, 15-18, 21, 22 the present study supports the conclusions that the thermal dediazoniation of arenediazonium salt in the presence of cyclic or acyclic polyether in solution occurs by an S N -like reaction mechanism 27 (Scheme 1) via two competing but independent pathways, with the formation of a highly reactive aryl cation in the heterolysis and/or an aryl radical in the homolysis in the slow ratedetermining decomposition step of the uncomplexed ion or the complex. Subsequent fast product-determining reactions with nucleophiles counterion, solvent and polyether give the products XC 6 H 4 F, XC 6 H 4 Y and XC 6 H 4 Z, respectively, presented in Scheme 1, where X is the substituent of the benzenediazonium ion.…”

“…The changes in polarity during the decomposition step of the uncomplexed and complexed benzenediazonium ion can be assumed to be small and thus the large positive ⌬V ‡ values for dediazoniation reactions are strong evidence for an S N 1-like reaction mechanism as proposed by Swain et al 27 Correspondingly, the values of the activation enthalpy ⌬H ‡ and the activation entropy ⌬S ‡ for the decomposition of the complexed ion are large, and clearly larger than the corresponding values for the dediazoniation of the uncomplexed ion, and suggest an isokinetic relationship for the heterolytic decomposition of an uncomplexed arenediazonium ion and one complexed with crown ethers or acyclic polyethers in various solvents. [16][17][18] .…”

Hydroxy- and chloro- dediazoniation of 2- and 3- methylbenzenediazonium tetrafluoroborate in aqueous solution

“…Substituent effects are not understandable on the basis of the Hammett equation, [12,29,38] because most para and meta substituents, including electronwithdrawing (like p ϭ NO 2 ) and electron-donating groups (like show a marked stabilizing 9 N(CH ) , 9 CH ) 3 2 3 effect, but they fit the Swain-Lupton [39] equation, which separates the resonance and inductive effects [9,12,40]. As shown in Table III, the effects of the methyl groups on dediazoniation rates are surprising, though modest.…”

Singlet–triplet excitation energies of substituted phenyl cations: a G4(MP2) and G4 theoretical study

“…The existence and energetics of aryl cations has long been a topic of interest among the organic chemistry community [1][2][3][4][5][6]. In particular, the nature of the ground state multiplicity for the parent and substituted phenyl cations has attracted considerable attention.…”