Aqueous mercury adsorption in a fixed bed column of thiol functionalized mesoporous silica

The aim of this work was to investigate the aqueous mercury adsorption in a fixed bed of mesostructured silica SBA-15 functionalized with propylthiol by co-condensation (SBA-15-SH). Powdered synthesized adsorbents were used to prepare pellets with sizes ranging from 0.5 to 1 mm. The physicochemical properties determined from N₂ adsorption and chemical analysis were compared for powder and pellets. Batch static experiments were carried out to obtain the equilibrium mercury adsorption isotherms, resulting that although the maximum adsorption capacity was reduced from powder to pellets, the materials maintained high efficiency for mercury removal even at very low aqueous metal concentration. Dynamic experiments were carried out in a fixed bed column by modifying the volumetric flow rate, bed length, inlet concentration, and amount of propylthiol groups incorporated to the adsorbent, and analyzing the temporal scale and the mercury adsorption capacities. The elution of the fixed bed was carried out chemically by circulating an aqueous 2 M hydrobromic acid stream for 2 h so achieving a complete recovery of the mercury previously adsorbed. Simplified dynamic equations of Bohart–Adams and Wolborska were used for modeling the breakthrough curves.     

Expanding the Scope of Hypervalent Iodine Reagents for Perfluoroalkylation: From Trifluoromethyl to Functionalized Perfluoroethyl

A series of new hypervalent iodine reagents based on the 1,3‐dihydro‐3,3‐dimethyl‐1,2‐benziodoxole and 1,2‐benziodoxol‐3‐(1H)‐one scaffolds, which contain a functionalized tetrafluoroethyl group, have been prepared, characterized, and used in synthetic applications. Their corresponding electrophilic fluoroalkylation reactions with various sulfur, oxygen, phosphorus, and carbon‐centered nucleophiles afford products that feature a tetrafluoroethylene unit, which connects two functional moieties. A related λ³‐iodane that contains a fluorophore was shown to react with a cysteine derivative under mild conditions to give a thiol‐tagged product that is stable in the presence of excess thiol. Therefore, these new reagents show a significant potential for applications in chemical biology as tools for fast, irreversible, and selective thiol bioconjugation.     

Eosin Y (EY) Photoredox‐Catalyzed Sulfonylation of Alkenes: Scope and Mechanism

Alkyl‐ and aryl vinyl sulfones were obtained by eosin Y (EY)‐mediated visible‐light photooxidation of sulfinate salts and the reaction of the resulting S‐centered radicals with alkenes. Optimized reaction conditions, the sulfinate and alkene scope, and X‐ray structural analyses of several reaction products are provided. A detailed spectroscopic study explains the reaction mechanism, which proceeds through the EY radical cation as key intermediate oxidizing the sulfinate salts.     

Unexpected reactivity of pyridinium salts toward alkynyl Fischer complexes to produce oxo‐heterocycles

The unprecedented reaction of ketone‐containing aromatic pyridinium salts 3a ‐ e and alkynyl Fischer complexes 1a ‐ f proceeds via a mild domino process to provide 4,6‐disubstituted pyran‐2‐ones 5a ‐ k and 2,3,5‐trisubstituted furans 6a ‐ h (45‐97%). According of the results of isotopic labeling experiments, a mechanism involving an initial Michael addition appears to be the key step, obtaining a mesomeric structure responsible for the formation of both products.