Reactivity with Carbon Dioxide

The afore-described Asahi Kasei technology best exemplifies the move to green and sustainable processes using carbon dioxide as feedstock. There 

Adapted with permission from ref. 101. Copyright 1991 American Chemical Society. 

It would be advantageous to directly react carbon dioxide with alcohols and polyols as they constitute carbon feedstocks available from nonfossil resources.Indeed, diorganotin(iv) compounds catalyse the carbojgrlation 

Complex (a) was isolated as a dimer. Carbon dioxide uptake was found to be reversible at room temperature and consists of the insertion of carbon dioxide into Sn-OiPr bond to form a monodentate allq lcarbonato ligand. Notably, an identical structure was characterised from [(CH3)2Sn(OCH3)2]2, which is also active for dimethyl carbonate formation in an excess of methanol and carbon dioxide at 180 °C and 30 MPa. In the distannoxane series, the structure of the isolated species (b) is also dimeric with a similar insertion of carbon dioxide into a Sn-OiPr bond to form a monodentate allq l carbonate ligand. Species (c) has a higher nuclearity of 10 tin atoms. 

The skeleton is made of Sn-O-Sn bonds and bridging metho and carbo-nato ligands. This species was isolated after catalytic runs producing dimethyl carbonate at 150 °C and 20 MPa, and was considered as the dormant species that can be recycled to the active species under catalytic conditions. 

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Lithium Oxide. Lithium oxide [12057-24-8], Li20, can be prepared by heating very pure lithium hydroxide to about 800°C under vacuum or by thermal decomposition of the peroxide (67). Lithium oxide is very reactive with carbon dioxide or water. It has been considered as a potential high temperature neutron target for tritium production (68). 

These latter workers liave demonstrated, by electrochemical experiments, the different reactivities of 125 and its cis isomer.Thus, whereas 125 is formed essentially reversibly and lost in a slow dimerization reaction and a slow coupling with unreduced thioindigo, its cis isomer is rapidly consumed in isomerization, radical-radical, and radical-parent coupling reactions. Similar differential reactivities with carbon dioxide, acrylonitrile, and cin-namonitrile were also observed. For 6,6 -diethoxytliioindigo, it was found that the electroreduction of the cis and trans isomers occurred at different... 

Consequently, we are in the startup phase of our program. Our first task was to identify candidate perovskite oxide materials with high protonic conductivities. We have identified ytterbium doped strontium cerate and yttrium doped strontium zirconate materials as possible electrolyte materials. Barium cerate perovskites exhibit higher protonic conductivity, but the reactivity with carbon dioxide would require pretreatment of the steam. 

Yet, alkaline electrolytes also have some severe disadvantages relative to acidic electrolytes. The most important disadvantage is their reactivity with carbon dioxide, which they readily absorb forming carbonates. As is always present in air, an... 

The kinetics of formation of [Co(tren)(C03)] from [Co(tren)(OH)2] have been investigated over the pH range 10.5-13. The tren system is very suitable for such a study, in a pH range where it is possible to assess the reactivity of CO3" as well as of HCOf and CO2, since it is stable both with respect to base hydrolysis and to redox reactions. Rate constants were measured over the temperature range 298-333 K at an ionic strength of 0.5 mol dm". It proved necessary to analyze the results in terms of three parallel reactions, since the high reactivity with carbon dioxide meant that reaction with this species had to be included despite its very low concentrations under these conditions. 

Schmeier TJ, Nova A, Hazari N, Maseras F. Synthesis of PCP-supported nickel complexes and their reactivity with carbon dioxide. Chem Eur J. 2012 18 6915-6927. 

Wu JG, Hazari N, Incarvito CD. Synthesis, properties, and reactivity with carbon dioxide of (aUyl)2Ni(L) complexes. Organometallics. 2011 30 3142-3150. 

Dead-burned magnesia, characterized by large crystaUite size and very low chemical reactivity, is resistant to the basic slags employed in the metals refining industry. It reacts very slowly with strong acids, and does not readily hydrate or react with carbon dioxide unless finely pulverized. 

Cobalt metal is significantly less reactive than iron and exhibits limited reactivity with molecular oxygen in air at room temperature. Upon heating, the black, mixed valence cobalt oxide [1308-06-17, Co O, forms at temperatures above 900°C the oHve green simple cobalt(II) oxide [1307-96-6] CoO, is obtained. Cobalt metal reacts with carbon dioxide at temperatures greater than 700°C to give cobalt(II) oxide and carbon monoxide. 

The reaction of peroxynitrite with the biologically ubiquitous C02 is of special interest due to the presence of both compounds in living organisms therefore, we may be confident that this process takes place under in vivo conditions. After the discovery of this reaction in 1995 by Lymar [136], the interaction of peroxynitrite with carbon dioxide and the reactions of the formed adduct nitrosoperoxocarboxylate ONOOCOO has been thoroughly studied. In 1996, Lymar et al. [137] have shown that this adduct is more reactive than peroxynitrite in the reaction with tyrosine, forming similar to peroxynitrite dityrosine and 3-nitrotyrosine. Experimental data were in quantitative agreement with free radical-mediated mechanism yielding tyrosyl and nitric dioxide radicals as intermediates and were inconsistent with electrophilic mechanism. The lifetime of ONOOCOO was estimated as <3 ms, and the rate constant of Reaction (42) k42 = 2 x 103 1 mol 1 s 1. 

Organoytterbium chemistry has been developed in the last 20 years, although the development rate is much slower than the other lanthanides like samarium or cerium. Dianionic complexes that are produced from the reaction of ytterbium with diaryl ketones react with various kinds of electrophiles including carbon-heteroatom unsaturated bonds.35 Phenylytterbium iodide, a Grignard-type reagent, is known to have reactivity toward carbon dioxide,36 aldehydes, ketones,37,37 and carboxylic acid derivatives38,3811 to form the corresponding adducts respectively. 

When designing an MCFC power system, several requirements must be met. An MCFC system must properly condition both the fuel and oxidant gas streams. Methane must be reformed into the more reactive hydrogen and carbon monoxide. Carbon deposition, which can plug gas passages in the anode gas chamber, must be prevented. To supply the flow of carbonate ions, the air oxidant must be enriched with carbon dioxide. Both oxidant and fuel feed streams must be heated to their proper inlet temperatures. Each MCFC stack must be operated within an acceptable temperature range. Excess heat generated by the MCFC stacks must be recovered and efficiently utilized. 

Phenoxide ion generated by treating phenol with sodium hydroxide is even more reactive than phenol towards electrophilic aromatic substitution. Hence, it undergoes electrophilic substitution with carbon dioxide, a weak electrophile. Ortho hydroj benzoic acid is formed as the main reaction product. 

Fig. 28. Effect of heat treatment on the reactivity of carbon derived from petroleum pitch. Reaction of 2 g. of 6 X 8-mesh carbon with carbon dioxide at 1100°. [After P. L. Walker, Jr., and J. R. Nichols, Industrial Carbon and Graphite, Society of Chemical Industry, p. 334. London, 1957.]...

The Grignard reagent is highly reactive and is used to prepare many functional groups. An example is the preparation of a carboxylic acid by reaction with carbon dioxide and mineral acid. 

PEG proves to be an efficient reaction medium for the reaction of vicinal halohydrin with carbon dioxide in the presence of a base to synthesize cyclic carbonates (Scheme 5.9) [42], Notably, PEG400 (MW = 400) as an environmentally friendly solvent exhibits a unique influence on reactivity compared with conventional organic solvents. Various cyclic carbonates can be prepared in high yield employing this protocol. The process presented here has potential applications in the industrial production of cyclic carbonates because of its simplicity, cost benefits, ready availability of starting materials, and mild reaction conditions. 

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