نتایج جستجو برای: protic acid
تعداد نتایج: 748132 فیلتر نتایج به سال:
Protic ionic liquids are synthesized via proton transfer from acids to organic bases. One of the key issues associated with conventional protic ionic liquids is the thermal instability resulting from temperature-induced decomposition via reverse proton transfer. This shortcoming significantly hampers the use of these protic ionic liquids in separations, electrochemical capacitors, fuel cells, a...
glucose. The influence of the solution acidity on the deconstruction of Miscanthus giganteus was examined by varying the 1-butylimidazole to sulfuric acid ratio. Increased acidity led to shorter preteatment times and resulted in reduced hemicellulose content in the pulp. Addition of water to the ionic liquid resulted in enhanced saccharification yields. The ability to tune acidity through the u...
Rate coefficients for terminal acetate (g-O2CCH3) substitution from the [Mo3(l3-O)2(l-O2CCH3)6 (g-O2CCH3)3] anion were examined in polar protic (D2O and methanol-d4), polar aprotic (DMSO-d6 and DMF-d7) and acidic solvents (acetic acid-d4). Reaction rates were determined using variable-temperature H NMR and found to span orders of magnitude depending on the solvent (k K (s!1) = 7.2 " 10!6 for D2...
Recently, dynamic approach has been applied to determine the steady state concentrations of multiple ionic species present in complex buffers at equilibrium. Here, we have used the dynamic approach to explicitly model the pH profiles of biologically relevant phosphate buffer and universal buffer (a mixture of three tri-protic acids such as citric acid, boric acid and phosphoric acid). The resul...
The regioselective gold-catalysed hydration of propargylic alcohols to β-hydroxy ketones can be achieved by diverting the gold-catalysed Meyer-Schuster rearrangement through the addition of a protic additive with a pKa of 7-9 such as p-nitrophenol, boric acid or a boronic acid. This provides an interesting alternative to an aldol reaction when combined with the straightforward addition of an al...
Earlier proposed a general approach using data mV/mL from a potentiometric titration is tested for the quantitative determination of mixtures of monoand poly-protic substances. The method is based on the treatment of the primary data with nonlinear regression procedure using commercial software which gives directly the analytical result. A general formula valid for every type of acid base titra...
An efficient protocol to synthesize iodohydrins from alkenes is presented. Reactions were conducted in aqueous media using safe and readily available sodium iodide (the most abundant form of the element), and a highly convenient oxidant such as hydrogen peroxide. Addition of a protic acid triggers a faster and efficient process, a role formally related to that played by haloperoxidase enzymes i...
The temperature dependence of the N-H proton chemical shift in protic ionic liquids (PILs) and FT-IR spectra of the N-H bonds indicated the presence of strong hydrogen bonds between the protonated cation and the anion, depending on the ΔpK(a) of the constituent acid and base, and their successive breaking with temperature, which may explain the characteristic properties of PILs such as relative...
The secretion from the hippopotamus’ skin changes its color from colorless to red, and then brown by polymerization of its pigments. The responsible pigments for the coloring reaction were isolated and denoted as hipposudoric acid (the red pigment) and norhipposudoric acid (the orange pigment). The syntheses of these pigments and the related derivatives were performed, and the latter were of us...
The synthesis of polyimides (PIs) containing polydimethylsiloxane (PDMS) with controlled chain length and the formation higher-order structures were studied. Polycondensation was carried out using diphenyl-3,3',4,4'-tetracarboxylic dianhydride (BPDA) diamine oligomers having amino groups on both ends PDMS. obtained poly(amic acid) (PAA) PI showed good solubility in several common polar solvents...
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