Low-barrier concerted electrophilic aromatic substitution under the action of sulfur trioxide

Aromatic sulfonation with sulfur trioxide: mechanism and kinetic model

“…As an alternative explanation for the first-order reaction in SO 3 in noncomplexing media, Morkovnik and Akopova suggested a relay-race mechanism involving a brønsted acid as a catalyst ( Scheme 2 ). 23 The plausibility of this mechanism is verified with rMD simulations of the benzene–SO 3 σ-complex, restrained at the C 1 –S 1 bond, in the presence of a H 2 SO 4 molecule. Spontaneous sulfonation takes place in all three environments within 170 ps ( Table 2 ), although the mechanism differs from the mechanism proposed previously 23 and depends on the polarity of the environment ( Fig.…”

“…Importantly however, it is not clear how the participation of two SO 3 molecules, as suggested previously, 12 , 21 fits in with the first order rate dependence on the SO 3 concentration in apolar solvent. Morkovnik and Akopova 23 have proposed an alternative low-barrier mechanism with one SO 3 in apolar solvent. In their proposal, a sulfuric acid molecule acts as a catalyst by transferring the proton from benzene to SO 3 via a relay-race mechanism ( Scheme 2 ).…”

Investigation of the sulfonation mechanism by gas–liquid interfacial plasma under atmospheric pressure conditions

“…Sulfur on SO 3 and HOSO 2 • are good electrophiles that can attack the edges and defects of carbon materials, forming sulfonic groups on the carbon network [6]. However, these reactions require a strong acid as the catalyst [39]. Therefore, carbon sulfonation in a plasma-1 M H 2 SO 4 environment achieved the best results.…”

Sulfonation Mechanism of Polysulfone in Concentrated Sulfuric Acid for Proton Exchange Membrane Fuel cell Applications

“…Though sulfonated polysulfone can be synthesized by postsulfonation of commercial polysulfone, the adequate sulfonation degree is difficult to achieve as the insufficient sulfonation will limit the overall proton conductivity, and oversulfonation will lead to chain-scission breakage of the polymeric backbone thus degradation of the molecular weight, the water resistance, and the chemical and mechanical performances. − Therefore, it is important to study the sulfonation mechanisms to improve the overall performances of sulfonated polysulfone. Galabov et al optimized the transition states of the sulfonation of aromatic molecules by SO 3 using high-level ab initio calculations and verified that the sulfonation is a trimolecular process consisting of one aromatic molecule and two SO 3 molecules. , Morkovnik and Akopova optimized the transition states for the processes of single-stage isomerization of bimolecular π complex that associates with a H 2 SO 4 molecule into corresponding associates of sulfonic acids, which indicated that the initial associates of the benzene π complex may result from the addition of bimolecular π complexes and H 2 SO 4 . Recently, Shi suggested that the trimolecular σ complex is formed directly from the rearrangement of a weak trimolecular π complex instead of the reaction of a bimolecular σ complex and SO 3 …”

“…32,33 Morkovnik and Akopova optimized the transition states for the processes of single-stage isomerization of bimolecular π complex that associates with a H 2 SO 4 molecule into corresponding associates of sulfonic acids, which indicated that the initial associates of the benzene π complex may result from the addition of bimolecular π complexes and H 2 SO 4 . 34 Recently, Shi suggested that the trimolecular σ complex is formed directly from the rearrangement of a weak trimolecular π complex instead of the reaction of a bimolecular σ complex and SO 3 . 35 In this work, we will study the sulfonation mechanisms of model molecules, which emulate the typical commercialized polysulfone, using concentrated H 2 SO 4 as the sulfonation agent on the basis of density functional theory (DFT) calculations.…”