Aromatic sulfonation with sulfur trioxide: mechanism and kinetic model

Abstract

Electrophilic aromatic sulfonation of benzene with sulfur trioxide is studied with ab initio molecular dynamics simulations in gas phase, and in explicit noncomplexing (CCl3F) and complexing (CH3NO2) solvent models.

A dynamic picture of the halolactonization reaction through a combination of ab initio metadynamics and experimental investigations

“…[51][52][53][54] Recently, we have shown the usefulness of rst-principles metadynamics (MtD) simulations to study the mechanisms of the electrophilic aromatic sulfonation and chlorination, with a focus on the formation of ionic intermediates during the reaction. 55,56 In this work, a similar approach will be used to revisit the mechanism of the non-catalysed halolactonization. Emphasis will be put on the formation of a possible ionic intermediate, which differentiates the NAAA mechanism from the classic two-step mechanism.…”

Solvent and Autocatalytic Effects on the Stabilisation of the σ‐Complex during Electrophilic Aromatic Chlorination

“…However, this was only possible when AlCl 3 was included as a Lewis acid catalyst in the static calculations . Nevertheless, multiple researchers have contested this classic mechanism and an alternative mechanism has been proposed, which does not include the formation of a Wheland‐type intermediate …”

“…For the static calculations, the solvent effects are taken into account implicitly using the SMD solvation model while metadynamics simulations allows us to take the solvent effects explicitly into account. Metadynamics has been shown to be a valuable tool in studying chemical reaction pathways in several cases . To get a thorough understanding of the solvent effects, a variety of environments are tested including gas phase, CCl 4 , acetonitrile and acetic acid.…”

Solvated proton as the main reagent and a catalyst in the single-stage aromatic sulfonation and protodesulfonation of sulfonic acids

“…The structure of this complex excludes the possibility of charge transfer from the benzene π‐system to the nitroxonium ion. However, Galabov et al, Koleva et al, and Moors et al did not find the formation of the arenium ion (σ‐complex) in any of these routes, although its existence has been recognized as essential in the literature . The conclusions of Galabov et al, Koleva et al, and Moors et al are in complete agreement with our views regarding the advantages of a single‐stage mechanism (via a cyclic transition state) for the electrophilic substitution of hydrogen into sulfonic groups in arenes in the forward reaction and for the electrophilic substitution of sulfonic groups into hydrogen in the inverse reaction in an aqueous acidic medium when comparing alternative schemes with the experiment (single‐stage and 2‐stage).…”

“…More recently, there was a series of studies that included results of an experimental study and quantum‐chemical calculations for the 3 types of electrophilic substitution of arenes: (1) halogenation with molecular chlorine and bromine, (2) nitration with a mixture of acids (nitric and sulfuric acid), and (3) sulfonation with SO 3 . In contrast to the established views in the literature, clear evidence was obtained that aromatic sulfonation with sulfur trioxide occurs via a concerted single‐stage mechanism and does not include formation of the accepted σ‐complex (Wheland complex) as an intermediate.…”