Carbon dioxide binding

Figure 9.25 Mechanism of carbonic anhydrase. The zinc-bound hydroxide mechanism for the hydration of carbon dioxide reveals one aspect of metal ion catalysis. The reaction proceeds in four steps (1) water deprotonation (2) carbon dioxide binding (3) nucleophilic attack of hydroxide on carbon dioxide and (4) displacement of bicarbonate ion by water.

On sampling, free dissolved carbon dioxide and its compounds are fixed as carbonate by filling the water samples into flasks which are charged with sodium hydroxide solution or calcium oxide. In closed apparatus in the laboratory, add acid to the weakly alkaline sample, liberating carbon dioxide, bind the carbon dioxide on soda-asbestos and weigh. 

Fujita E, Szalda DJ, Creutz N, Sutin N (1988) Carbon dioxide activation thermodynamics of carbon dioxide binding and the involvement of two cobalt centiax in the reduction of carbon dioxide by a cobalt(I) macrocycle. J Am Chem Soc 110 4870-4871... 

Creutz C, Schwarz HA, Wishart JF, Fujita E, Sutin N (1991) Thermodynamics and kinetics of carbon dioxide binding to two stiaeoisomers of a cobalt(I) mataocycle in aqueous solution. J Am Chem Soc 113 3361-3371... 

Creutz, C. 1993. Carbon Dioxide Binding to Transition-Metal Center. Pp. 19-67 in Electrochemical and Electrocatalytic Reactions of Carbon Dioxide, B.P. Anllivan, Amsterdam Elsevier. 

M. are the most important organisms in maintaining ecological equilibrimn in the world by their enormous synthetic potential 90% of carbon dioxide binding by photosynthesis is carried out by m. under the surface of the sea. 

Direct binding of CO2 to haemoglobin accounts for only about 10 per cent of the physiological transport of CO2. Carbon dioxide binds to both oxy- and deoxyhaemoglobin by interaction with amino groups in the protein to form carbamate groups ... 

Question. For X-ray photoelectron spectra of a mixture of acetone and carbon dioxide gases, explain what you would expect to observe regarding the relative ionization energies (binding energies) and intensities in the C Is and O Is spectra. 

Carbon dioxide has an effect on Og binding by Hb that is similar to that of partly because it produces when it dissolves in the blood carbonic anhydrase ... 

Figure 6-9. The Bohr effect. Carbon dioxide generated in peripheral tissues combines with water to form carbonic acid, which dissociates into protons and bicarbonate ions. Deoxyhemoglobin acts as a buffer by binding protons and delivering them to the lungs. In the lungs, the uptake of oxygen by hemoglobin releases protons that combine with bicarbonate ion, forming carbonic acid, which when dehydrated by carbonic anhydrase becomes carbon dioxide, which then is exhaled.

Poisoning of platinum fuel cell catalysts by CO is undoubtedly one of the most severe problems in fuel cell anode catalysis. As shown in Fig. 6.1, CO is a strongly bonded intermediate in methanol (and ethanol) oxidation. It is also a side product in the reformation of hydrocarbons to hydrogen and carbon dioxide, and as such blocks platinum sites for hydrogen oxidation. Not surprisingly, CO electrooxidation is one of the most intensively smdied electrocatalytic reactions, and there is a continued search for CO-tolerant anode materials that are able to either bind CO weakly but still oxidize hydrogen, or that oxidize CO at significantly reduced overpotential. 

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