Mechanisms of Benzyl Group Transfer in the Decay of (E)-Arylmethanediazoates and Aryldiazomethanes in Aqueous Solutions

Solvolysis of Some Arenediazonium Salts in Binary EtOH/H2O Mixtures under Acidic Conditions

“…[38] Such low values are orders of magnitude lower than those observed for nucleophiles competing with water in reactions with stabilized carbocations, [23,40,41] and they are consistent with the formation of highly reactive aryl cations and with the stepwise preassociation mechanism shown in Scheme 1. The data in Figure 4 [39] are sufficiently small that the product distribution reflects the solvent distribution in the first solvation shell of the reactant. This is consistent with the relatively modest variation in k obs on going from water to ethanol, suggesting that the solvation of the ground state is essentially the same as that in the proximity of the transition state; that is, ∆G # is not significantly affected by solvent composition.…”

“…[32] With lifetimes in the nanosecond order of magnitude, aryl cations do not have time to diffuse away, and hypothetical preassociation of the nucleophile with the precursor would not account for much of the trapping, as it happens with other extremely short lived carbocations behave. [39] Thus, in the absence of specific interactions, arenediazonium ions will decompose mainly through the solvated aryl cations; that is, upon unimolecular removal of N 2 , one nucleophile molecule of the first coordi-nation shell will form the corresponding dediazoniation product. In other words, to obtain a specific dediazoniation product, the corresponding nucleophile molecule must be present in the solvation shell of the aryl cation prior to N 2 splitting from the precursor.…”

Solvolyses of 4‐methylbenzenediazonium ions in trifluoroethanol/water mixtures: Effects of [TFE], acidity and temperature on the kinetics and mechanism of the reaction

“…Rate constants for nucleophilic attack on carbocations have been reported to be close to the diffusion control limit, ∼10 9 –10 13 M −1 s −1 29. Aryl cations have lifetimes on the order of nanoseconds and they do not have much time to diffuse away reorganizing their nearest neighbour ions and molecules, similar to the behaviour of other extremely short‐lived carbocations 35. Thus, at a low concentration of other components, e.g.…”

Dediazoniation of 1‐naphthalenediazonium tetrafluoroborate in aqueous acid and in micellar solutions

“…Rate constants for nucleophilic attack on carbocations have been reported to be close to the diffusion control limits, ∼10 9 to 10 13 M −1 s −1 43. With lifetimes in the nanosecond order of magnitude, aryl cations do not have time to diffuse away and a hypothetical preassociation of the nucleophile with the precursor would not account for much of the trapping, in a similar fashion than other extremely short‐lived carbocations behave 44. Thus, in the absence of specific interactions, arenediazonium ions will decompose mainly through the solvated aryl cations, i.e., upon unimolecular removal of N 2 , one nucleophile molecule of the first coordination shell will form the corresponding dediazoniation product.…”