Glycosyl Bunte Salts: A Class of Intermediates for Sugar Chemistry.
S-Glycosyl thiosulfates have been discovered as a new class of synthetic intermediates in sugar chemistry, named "glycosyl Bunte salts" after 19th-century German chemist, Hans Bunte. The synthesis was achieved by direct condensation of unprotected sugars and sodium thiosulfate using a formamidine-type dehydrating agent in water-acetonitrile mixed solvent. The application of glycosyl Bunte salts is demonstrated with transformation reactions into other glycosyl compounds such as a 1-thio sugar, a glycosyl disulfide, a 1,6-anhydro sugar, and an O-glycoside.
Promoting Effect of Crystal Water Leading to Catalyst-Free Synthesis of Heteroaryl Thioether from Heteroaryl Chloride, Sodium Thiosulfate Pentahydrate, and Alcohol.
It is observed the crystal water in sodium thiosulfate pentahydrate (Na2S2O3•5H2O) can promote its multi-component reaction with heteroaryl chlorides and alcohols, providing a facile, green and specific synthesis of unsymmetrical heteroaryl thioethers via one-step formation of two C-S bonds under catalyst-, additive-, and solvent-free conditions. Mechanistic studies suggest that the crystal water in Na2S2O3•5H2O is crucial in generating the key thiol intermediates and byproduct NaHSO4, which then catalyzes the dehydrative substitution of alcohols with thiols to afford thioethers.
Enhancement of surface properties on Low Density Polyethylene packaging films using various fluorination routes
Nowadays, packaging market deployment requires an important attention. Influence of treatment with molecular (F2) or atomic (Fradical dot) fluorine on properties of Low Density Polyethylene (LDPE) films was investigated. The films were treated using direct fluorination conditions with F2 or a specific reagent XeF2, which releases atomic fluorine Fradical dot. Changes of LDPE chemical composition were investigated by FTIR and solid state NMR. Surface morphology was studied by several microscopy techniques (SEM and AFM). Finally to further characterize film properties after treatments, surface energy measurements and electron paramagnetic resonance (EPR) analyses were also carried out. An upper fluorinated layer, which contains mainly high amount of single bondCF2single bond, was formed during the direct fluorination conditions (F2). For the process performed with XeF2, specific groups single bondCHFsingle bond were detected not only on the polymer surface but also in the bulk. The final CHF/CF2 ratio depended on the fluorination route. Treatment with Fradical dot (originated from XeF2 decomposition) resulted in single bondCHFsingle bond groups in bulk prevailing formation whereas F2 formed mainly single bondCF2single bond groups. Regardless to the reactive species, radicals (dangling bonds) appeared during the fluorination and reacted with oxygen during the exposition to air after the treatment. Such a process resulted in oxygenated polar groups formation and consequently in the surface energy increase.