Oxide protonation

The oxidation of water to dioxygen occurs as the consequence of Photosystem 11-dependent generation of a very strong oxidant. Protons liberated by the water-oxidation reaction then contribute to the thylakoid transmembrane electrochemical gradient that drives ATP synthesis. Brudvig et aL describe how flash-induced proton-release measurements have resolved key steps that provide insights on how the 02-evolving center of PSll mediates this four-electron oxidation of water. 

HBr + H- H- + Br2 — HBr + Br. properties The characteristics of matter Examples vapor pressure color density temperature, protective oxide An oxide that protects a metal from oxidation. Example aluminum oxide, proton p A positively charged subatomic particle found in the nucleus of an atom, protonation Proton transfer to a Bronsted base. Example 2 H30+(aq) + S2-(s) — ... 

The initial proton release associated with H2 cleavage is promoted by a base. For hydrogen evolution, net proton uptake from the medium is necessary. Conversely, for Hj oxidation protons are transferred from the active site to solution. The transfer of protons within a protein is considered to involve small (<1 ) movements of the amino acids that participate in the pathway (Williams, 1995). The proton transfer would involve a rotation of each individual donor and acceptor. Analyses of the crystal structures have suggested proton transfer pathways for the NiFe and Fe-only hydrogenases. 

Strongly oxidizing protonated form Less oxidizing unprotonated form... 

Agreement between theoretical and experimental TJT2 values is much poorer for X = Br and I and indicates a breakdown of the Redfield theory. (32) Isotropic proton shifts for pyridine-N-oxide and y-picoline-A-oxide protons have been reported in the 5-coordinated adducts of these bases with bis(di-p-tolyl-dithiophosphinato)-Co(ii) and -Ni(ii). (70,71) Dipolar shifts have been evaluated and indicate that the Co(ii)-pyridine-N-oxide adducts have a bent structure in solution with Co-O-N angle of 125°. Results indicate that a rr-spin delocalization mechanism is operating, and INDO calculations suggest that the highest bonding orbital is involved in the spin transfer process. 

Each of these fuel cells are named or defined by the electrolyte used in them, that is alkaline, phosphoric acid, molten carbonate, solid oxide, proton exchange membrane, etc. 

Fukatsu, N. and Kurita, N. (2005) Hydrogen sensor based on oxide proton conductors and its application to metallurgical engineering. Ionics, 11, 54-65. 

Kurita, N., Fukatsu, N., Miyamoto, S., Sato, F., Nakai, H., Irie, K. and Ohashi, T. (1996) The measurement of hydrogen activities in molten copper using oxide protonic conductor. Metall. Mater. Trans. B, -a, 929-35. 

Pyridine iV-oxides protonate and are alkylated at oxygen stable salts can be isolated in some cases. 0-Alkylation with benzylic and allylic halides in the presence of silver oxide produces the corresponding aldehydes, the oxygen being derived from the iV-oxide. " ... 

M EXPERIMENTAL FIGURE 8-19 Electron transfer from reduced cytochrome c (Cyt c " ) to O2 via the cytochrome c oxidase complex is coupled to proton transport. The oxidase complex is incorporated into liposomes with the binding site for cytochrome c positioned on the outer surface, (a) When O2 and reduced cytochrome c are added, electrons are transferred to O2 to form H2O and protons are transported from the inside to the outside of the vesicles. Valinomycin and are added to the medium to dissipate the voltage gradient generated by the translocation of H, which would otherwise reduce the number of protons moved across the membrane, (b) Monitoring of the medium pH reveals a sharp drop in pH following addition of O2. As the reduced cytochrome c becomes fully oxidized, protons leak back into the vesicles, and the pH of the medium returns to its initial value. Measurements show that two protons are transported per O atom reduced. Two electrons are needed to reduce one O atom, but cytochrome c transfers only one electron thus two molecules of Cyt c are oxidized for each O reduced. [Adapted from B. Reynafarje et al., 1986, J. Biol. Chem. 261 8254.1... 

The principal goal of this project is to demonstrate electrolysis technology using ceramic electrochemical cells based on solid oxide proton conductors. Los Alamos National Laboratory (LANL) has experience in solid-state bulk and thin... 

Yttria-doped zirconia and gadolinia-doped ceria oxygen ion conductors and strontium yttrium zirconium oxide proton conductors are being investigated as the solid electrolyte. 

Finally, in protonated pemigraniline, the band at 3.8 eV disappears completely and a polaron lattice character was assumed for fully oxidized protonated PANl, with two bands at 2.2 and 4.3 eV [55] but the reality of this kind of structure is not demonstrated. 

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