Cesium 3,5-bis(2,4,6-tri-tert-butylphenyl)-1,2,4-triphospholide (12) and cesium 5-(2,4,6-tri-tert-butylphenyl)tetraphospholide (13) were synthesized and isolated with flat fivemembered rings, which are an indication of the aromaticity in these anions. Compound 13 is the first example of a stable tetraphospholide anion, which is structurally characterized. Kinetic stabilization of the 1,2,4-triphospholide system by
In recent years, metal−metal oxide catalysts have proven to be robust catalysts for hydrodeoxygenation (HDO) of oxygenated compounds derived from biorenewable feedstocks to value-added products. Herein, the conversion of 1,2,6-hexanetriol (1,2,6-HT) to 1,6-hexanediol (1,6-HD) in aqueous media over a Pt-WO x /TiO 2 catalyst is examined via isotope incorporation in HDO of a model compound, 1,2-pentanediol (1,2-PD). Absence of a primary kinetic isotope effect (k H /k D = 0.84 ± 0.11) disproves a potential direct C−O bond scission mechanism. The observation of nearly complete deuterium incorporation in both the α-C and the β-C is inconsistent with the reverse Mars−van Krevelen mechanism and suggests an enol formation pathway. Evidence consistent with the intermediacy of an oxocarbenium ion as a minor contributor has also been observed. In drawing the conclusions, it was necessary to characterize the facile isotope exchange between surface activated hydrogen and the water solvent. Hydrogenation of a water-soluble olefin, tetra(ethylene glycol) diacrylate (TEGDA) in H 2 /D 2 O revealed predominant incorporation of deuterium instead of hydrogen in the reduced product, confirming the rapid exchange of surface activated hydrogen. The methods used in this study provide clarification about a reaction mechanism currently under debate, and these findings can be applied to other systems involving HDO of linear polyols over metal−metal oxide catalysts, improving catalyst design and utilization of sustainable feedstocks.
Acetates of α‐1,3‐glucan dissolved in N,N‐dimethyl acetamide/LiCl are prepared by converting the polysaccharide with acetyl chloride, acetic acid anhydride/pyridine, or with acetic acid/N,N′‐carbonyl diimidazole. Values of the degree of substitution for the acetyl groups (DSAc) of up to 2.6 are realized. NMR spectroscopic measurements reveal a preferred conversion of the primary hydroxyl group at position 6 followed by positions 2 and 4. Depending on the DSAc, the samples may be soluble in solvents of different polarity at room temperature or at elevated temperatures showing upper critical solution temperature at DS of about 2.5. This process is found to be reversible.
Several water-soluble polymers were used as templates for the in situ polymerization of pyrrole to determine their effect on the generation of nanosized polypyrrole (PPy) particles. The polymers used include: polyvinyl alcohol (PVA), polyethylene oxide (PEO), poly(vinyl butyral), polystyrene sulfonic acid, poly(ethylene-alt-maleic anhydride) (PEMA), poly(octadecene-alt-maleic anhydride), poly(N-vinyl pyrrolidone), poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate), poly(N-isopropyl acrylamide), poly(ethylene oxide-block-propylene oxide), hydroxypropyl methyl cellulose, and guar gum. The oxidative polymerization of pyrrole was carried out with FeCl 3 as an oxidant. The morphology of PPy particles obtained after drying the resulting aqueous dispersions was examined by optical microscopy, and selected samples were further analyzed
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