Surface reactions of carbon dioxide at the adsorbed water-iron oxide interface

Despite the fact that carbon dioxide is an abundant atmospheric gas with profound environmental implications, there is little information on the reaction of carbon dioxide at the adsorbed water-oxide interface. In this study, the chemistry of carbon dioxide at the adsorbed water-iron oxide interface is investigated with FTIR spectroscopy. As shown here, the thin water layer on the iron oxide surface plays an important role in the surface chemistry of carbon dioxide. In particular, adsorbed water enhances CO(2) uptake, undergoes isotope exchange with CO(2) in O(18)-labeled experiments, and influences the chemical nature of the predominant adsorbed product on the surface from bicarbonate to carbonate. The resultant thin water film is acidic in nature from the reaction of CO(2). The IR spectrum recorded of adsorbed carbonate at the adsorbed water-iron oxide interface is remarkably similar to that at the bulk liquid water-iron oxide interface. Since reactions in thin water films estimated to be approximately 2 layers will play a role in a number of environmental processes, it is essential to understand the chemistry of these "wet" interfaces with atmospheric gases.     

Photogeneration of carbon dioxide from polypropylene film stabilized by hindered amines

Infrared spectrometric measurements have been used to measure the amount of carbon dioxide generated by UVA irradiation of polypropylene film stabilized with 0.5% of three different hindered amine light stabilizers (HALS). The measurements were made in situ, using a specially constructed glass cell fitted with CaF₂ windows. In each case the amount of photogenerated carbon dioxide was less than that from a HALS-free polypropylene film of similar thickness. The amount of photogenerated CO₂ was greatest in oxygen that had been pre-saturated with water and the amount of CO₂ evolved depended on the grade of HALS. In dry oxygen, although the differences between the films containing different HALS were much reduced the amount of CO₂ continued to be smaller than that from the HALS-free polymer. The sensitivity of CO₂ photogeneration to the presence of HALS provides new evidence of the relevance of the CO₂ photogeneration method to the diagnosis of photosensitivity of polymers and the influence of stabilizing additives.     

Transition-metal-catalyzed reactions of propargylamine with carbon dioxide and carbon disulfide.

The reactions of propargylamine derivatives with carbon dioxide and carbon disulfide have been systematically examined in the presence of transition-metal catalysts. Pd(OAc)(2) is the best catalyst for the formation of the corresponding oxazolidinones. In addition, we found that, in the reaction of propargylamine with carbon dioxide catalyzed by palladium(0) metal catalyst in toluene, both oxazolidinone 1 and imidazolidinone 2 could be obtained under mild reaction conditions at the same time. The reaction of 1 with primary and secondary amines has been examined. A plausible reaction mechanism for the formation of 2 was proposed. In addition, in this paper, we first disclosed the ligand's effect on this reaction. Using PBu(t)(3) as a ligand with Pd(2)(dba)(3), 1 was exclusively formed in 90% yield.     

n-Butyllithium-mediated synthesis of N-aryl tertiary amines by reactions of fluoroarenes with secondary amines at room temperature

A simple and facile method for the synthesis of aromatic tertiary amines by amination of fluoroarenes with secondary amines in the presence of n-butyllithium at room temperature was reported.     

Interaction of hydrosilanes with carbon dioxide and secondary amines or silylamines

The reaction of hydrosilanes with carbon dioxide and secondary amines or silylamines was studied for the first time. The dependence of the composition and the structure of the products obtained on the nature of the reagents and on the reaction conditions was found. The hydrosilane-carbon dioxide system, unknown previously, can be used as anN-siloxycarbonylating reagent in the synthesis ofO-silylurethanes. A scheme for the formation ofO-silylurethanes was proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2309–2312, September, 1996.     

Pictet-Spengler reactions in multiphasic supercritical carbon dioxide/CO2-expanded liquid media. In situ generation of carbamates as a strategy for reactions of amines in supercritical carbon dioxide

Acyl-Pictet-Spengler cyclizations can be achieved in scCO2/CO2-expanded liquid media via the in situ formation of carbamate derivatives of beta-arylethylamines.     

Accelerated microdroplet synthesis of benzimidazoles by nucleophilic addition to protonated carboxylic acids

We report a metal-free novel route for the accelerated synthesis of benzimidazole and its derivatives in the ambient atmosphere. The synthetic procedure involves 1,2-aromatic diamines and alkyl or aryl carboxylic acids reacting in electrostatically charged microdroplets generated using a nano-electrospray (nESI) ion source. The reactions are accelerated by orders of magnitude in comparison to the bulk. No other acid, base or catalyst is used. Online analysis of the microdroplet accelerated reaction products is performed by mass spectrometry. We provide evidence for an acid catalyzed reaction mechanism based on identification of the intermediate arylamides. Their dehydration to give benzimidazoles occurs in a subsequent thermally enhanced step. It is suggested that the extraordinary acidity at the droplet surface allows the carboxylic acid to function as a C-centered electrophile. Comparisons of this methodology with data from thin film and bulk synthesis lead to the proposal of three key steps in the reaction: (i) formation of an unusual reagent (protonated carboxylic acid) because of the extraordinary conditions at the droplet interface, (ii) accelerated bimolecular reaction because of limited solvation at the interface and (iii) thermally assisted elimination of water. Eleven examples are shown as evidence of the scope of this chemistry. The accelerated synthesis has been scaled-up to establish the substituent-dependence and to isolate products for NMR characterization.

We report a metal-free novel route for the accelerated synthesis of benzimidazole and its derivatives in the ambient atmosphere.     

Competitive reactions of coordinated carbon monoxide and methyl isocyanide with amines

The relative reactivities of CO and CNR ligands with CH₃NH₂ were investigated in complexes which contained both ligands. Like (C₅H₅Fe(CO)₃⁺; the (C₅H₅)Fe(CO)₂(CNCH₃)⁺ complex reacts with CH₃NH₂ to give the carbamoyl complex (C₅)Fe(CO)(CNCH₃)(CONHCH₃); this is a readily reversible reaction. In contrast, (C₅H₅)Fe(CO)(CNCH₃)₂⁺ reacts with CH₃NH₂ to give the amidinium or carbene complex, (C₅H₅)Fe(CO)(CNCH₃)[C(NHCH₃)₂]⁺]. In a slow reaction, (C₅H₅)Fe(PPh₃)(CO)(CNCH₃)⁺ forms the amidinium complex, (C₅H₅)Fe(PPh₃)(CO)[C(NHCH₃)₂]⁺. Factors that affect the site of CH₃NH₂ reaction are discussed. The complexes have been characterized by IR and NMR spectroscopy; a variable temperature NMR study of (C₅H₅)Fe(CO)(CNCH₃)[C(NHCH₃)₂]⁺ indicates restricted rotation around the CN bonds of the amidinium ligand.     

Electron-transfer reactions at the plasma-liquid interface

Electrochemical reactions are normally initiated in solution by metal electrodes such as Pt, which are expensive and limited in supply. In this Communication, we demonstrate that an atmospheric-pressure microplasma can act as a gaseous, metal-free electrode to mediate electron-transfer reactions in aqueous solutions. Ferricyanide is reduced to ferrocyanide by plasma electrons, and the reduction rate is found to depend on discharge current. The ability to initiate and control electrochemical reactions at the plasma-liquid interface opens a new direction for electrochemistry based on interactions between gas-phase electrons and ionic solutions.     

Electronic states at the silicon-silicon dioxide interface

Localized electronic states at the silicon/silicon dioxide interface are reviewed, and the current knowledge of interface states and fixed oxide charges, and how they influence the characteristics of the MOS structure, is summarized. Experimental results on the properties of these two classes of localized states are presented and discussed. General trends of properties over a very extensive amount of data are noted and an overall picture of these states is given. Various phenomenological models for these electronic states are reviewed and critically discussed. It is pointed out that the current understanding of localized states is, in general, far from satisfactory, and a complete picture is lacking. Theoretical efforts on computing the energy levels of these electronic states are summarized. Most of these approaches are based on highly simplified structures, such as a simple unit cell with an atom missing. While they have been moderately successful, more realistic approaches are still needed. Finally, some theoretical techniques are introduced, in the hope that they may have applications to these problems, and the need for more measurements of non-electrical properties of these states is emphasized.     

Catalytic reactions of hydrocarbon with carbon dioxide over metallic catalysts

The catalytic reaction between hydrocarbons and carbon dioxide, e.g. CH₄+ +CO₂2CO+2H₂ and C₆H₆CH₃+CO₂C₆H₆+2CO+H₂, has been investigated over various metallic catalysts under atmospheric pressure. In general, Rh–Al₂O₃ catalyst was found to be excellent in activity and selectivity. The reaction rates were moderately dependent on the pressure of carbon dioxide, whereas it was little influenced by the pressure of hydrocarbon.

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, ., CH₄+CO₂2CO+2H₂ C₆H₅CH₃+CO₂C₆H₆+2CO+X₂, . , Rh–Al₂O₃ . , .

     

Low-temperature synthesis of tetraalkylureas from secondary amines and carbon dioxide

The reaction of dialkylamines with CO(2) giving tetraalkylureas can be performed at 60 degrees C. The reaction requires CCl(4), is weakly promoted by DMAN or PPh(3), and is not promoted by a Pd catalyst. A two-step procedure, in which dialkylammonium dialkylcarbamate is produced in situ and then reacted with CCl(4) and free dialkylamine, gave greater yields of urea than a simple single-stage procedure.     

Palladium-mediated cross-coupling reactions with supported reagents in supercritical carbon dioxide

Commercially available polystyrene supported amine and phosphine resins facilitate palladium-mediated Heck and Suzuki reactions in supercritical carbon dioxide (scCO2).     

Studies on reactions of the N-phosphonium salts of pyridines—XV : Direct carbonylation of amines with carbon dioxide by a hydrolysis-dehydration reaction with phosphorus compounds

Carbon dioxide reacts with amines in the presence of phosphorus compounds and tertiary amines to give the corresponding ureas in high yield, and carbon disulfide gave thioureas. The presence of tertiary amines such as pyridine or imidazole facilitated the reactions. Aryl esters of phosphorous, phosphonous, phosphinous and phosphonic acids were effective, whereas their corresponding alkyl esters were ineffective. Various molar ratios of phosphite:tartiary amine:amine (aniline), produced variations in yield showing that the reaction proceeds via a carbamoyloxy and a thiocarbamoylthioxy N-phosphonium salt of the tertiary amine.     

Local corrosion of magnesia-chrome refractories driven by Marangoni convection at the slag-metal interface

The local corrosion of magnesia-chrome refractories containing MgO-Al(2)O(3) spinel has been investigated near the slag-metal interface by immersion tests. The local corrosion extent near the slag-metal interface was found to decrease with the increase of FeO, MgO, and Al(2)O(3) contents in the slag. The local corrosion depths in the diagonal direction on the cross sections of the square prism specimens were always 2 times those in the normal direction of the lateral faces, and the cross sections maintained their initial square shape during whole the corrosion duration. The local corrosion is reckoned to be driven by the Marangori convection, which accelerated the mass transfer of the components dissolved from the refractories.