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Abstract: The polymer PEDOT+ (1 or 2) mediates a cyclodehydration reaction with alditols 3, 5, 7, 9, in hydrocarbon solvents, to give cyclic ethers 4, 6, 8, or 10, respectively, in high yield with a trivial isolation protocol. Polymers 1 or 2 also mediate the cyclodehydration of ketohexoses such as d-fructose, but not aldohexoses, to the important industrial intermediate 5-hydroxymethylfurfural (17), under milder conditions when compared to reactions mediated by mineral acids. A cascade reaction with ketohexoses is observed in toluene via cyclodehydration followed by Friedel–Crafts alkylation of the initially formed benzylic alcohol to give 16. [Copyright &y& Elsevier]

Abstract: The kinetics of the reduction of chromium(VI) to chromium(III) by d-fructose in HClO4 was studied at various concentrations of reactants and acidities. The redox reaction takes place through a complex multistep mechanism, which involves the formation of intermediate CrIV and CrV species. CrIV reacts with d-fructose much faster than CrV and CrVI do, and cannot be directly detected. Superoxochromium(III), , has been detected by UV spectroscopy, thus evidencing that CrII is an intermediary in these reactions and provides indirect evidence for the intermediary of CrIV reaction path. The complete rate law for the CrVI oxidation reaction is expressed by −d[CrVI]/dt =(a + b [d-Fru])[H+]2 [CrVI]T, where a =(1.66±0.04)×10−4 M−2 s−1 and b =(1.79±0.06)×10−2 M−3 s−1. The EPR spectra show that five-coordinate oxo-CrV bischelates are formed in rapid pre-equilibria before the redox step: Cr(V) to Cr(III). [Copyright &y& Elsevier]

Experimental data for the synthetic methods of preparation of the l-ketohexoses have been lacking an analytical method for monitoring the chemical or enzymatic reactions described. Dual refractive index and laser-based chiroptical detection provides an ideal method for following the reactions, since the refractive index detector quantifies the amount of analyte, while the ratio of optical rotation to refractive index response allows the enantiomer mole fraction to be determined. Sulfonated polystyrenedivinylbenzene resin in the Ca form as the stationary phase with H2O at 80 °C as the eluent gives base-line separation of sorbose, fructose, tagatose, and psicose. Dependent on the complexity of the reaction mixture, analysis times range from 20 to 60 min. [Copyright &y& Elsevier]