The electrochemical oxidation and reduction of nitrate ions in the room temperature ionic liquid [C(2)mim][NTf2]; the latter behaves as a 'melt' rather than an 'organic solvent'

The electrochemical oxidation of 1-butyl-3-methylimidazolium nitrate [C(4)mim][NO3] was studied by cyclic voltammetry in the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [C(2)mim][NTf2]. A sharp peak was observed on a Pt microelectrode (d = 10 mu m), and a diffusion coefficient at infinite dilution of ca. 2.0 x 10(-11) m(2) s(-1) was obtained. Next, the cyclic voltammetry of sodium nitrate (NaNO3) and potassium nitrate (KNO3) was studied, by dissolving small amounts of solid into the RTIL [ C2mim][ NTf2]. Similar oxidation peaks were observed, revealing diffusion coefficients of ca. 8.8 and 9.0 x 10(-12) m(2) s(-1) and solubilities of 11.9 and 10.8 mM for NaNO3 and KNO3, respectively. The smaller diffusion coefficients for NaNO3 and KNO3 (compared to [C(4)mim][NO3]) may indicate that NO3- is ion-paired with Na+ or K+. This work may have applications in the electroanalytical determination of nitrate in RTIL solutions. Furthermore, a reduction feature was observed for both NaNO3 and KNO3, with additional anodic peaks indicating the formation of oxides, peroxides, superoxides and nitrites. This behaviour is surprisingly similar to that obtained from melts of NaNO3 and KNO3 at high temperatures ( ca. 350 - 500 degrees C), and this observation could significantly simplify experimental conditions required to investigate these compounds. We then used X-ray photoelectron spectroscopy (XPS) to suggest that disodium( I) oxide (Na2O), which has found use as a storage compound for hydrogen, was deposited on a Pt electrode surface following the reduction of NaNO3.

A review of the selective reduction of NOx, with hydrocarbons under lean-burn conditions with non-zeolitic oxide and platinum group metal catalysts

Research on the selective reduction of NOx with hydrocarbons under lean-burn conditions using non-zeolitic oxides and platinum group metal (PGM) catalysts has been critically reviewed. Alumina and silver-promoted alumina catalysts have been described in detail with particular emphasis on an analysis of the various reaction mechanisms that have been put forward in the literature. The influence of the nature of the reducing agent, and the preparation and structure of the catalysts have also been discussed and rationalised for several other oxide systems. It is concluded for non-zeolitic oxides that species that are strongly adsorbed on the surface, such as nitrates/nitrites and acetates, could be key intermediates in the formation of various reduced and oxidised species of nitrogen, the further reaction of which leads eventually to the formation of molecular nitrogen. For the platinum group metal catalysts, the different mechanisms that have been proposed in the literature have been critically assessed. It is concluded that although there is indirect, mainly spectroscopic, evidence for various reaction intermediates on the catalyst surface, it is difficult to confirm that any of these are involved in a critical mechanistic step because of a lack of a direct quantitative correlation between infrared and kinetic measurements. A simple mechanism which involves the dissociation of NO on a reduced metal surface to give N(ads) and O(ads), with subsequent desorption of N-2 and N2O and removal of O(ads) by the reductant can explain many of the results with the platinum group metal catalysts, although an additional contribution from organo-nitro-type species may contribute to the overall NOx reduction activity with these catalysts.

Reactivity of 1,2-cyclic sulfite xylosides towards nucleophiles

1,2-Cyclic sulfite xylosides offer facile access to 1,2-oxazolines upon reaction with aromatic and alkyl nitrites under Lewis or Bronsted acid conditions. Additionally, hydrophobic ionic liquids facilitate acid-catalysed formations of such oxazolines and C- and O-linked xylosides, providing means to carry out fast reactions at room temperature, and this in yields comparable to reactions conducted in xylene at high temperature for extended reaction time. (c) 2009 Elsevier Ltd. All rights reserved.

Pre-enrichment of modified low density lipoproteins with alpha-tocopherol mitigates adverse effects on cultured retinal capillary cells

We determined whether pre-enrichment of low density lipoproteins (LDL) with alpha-tocopherol mitigates their adverse effects, following in vitro glycation, oxidation or glycoxidation, towards cultured bovine retinal capillary endothelial cells (RCEC) and pericytes.