Dimerization, oxygen

Dimerization (oxygen with CuCl in pyridine) of E- and Z-4-FcCH=CH C6H4C=CH gave the E,E- and Z,Z,-diynes, respectively, in >95% yield. " ... 

Shutilova, N. I. (2000), Mechanism of photosynthetic oxidation of water in a dimeric oxygen-evolving complex of photosystem II of chloroplasts, Biofizika 45, 51-57. 

HIF-la and HIF-2a have the same domain architecture and common mechanisms for DNA binding, dimerization, oxygen-dependent degradation (NODD and CODD domains), and transactivation domains. The sequences of these domains are related closely but contain differences that may have functional consequences (e.g., with respect to HIF hydroxylase selectivity). The interdomain sequences are related less closely, and the differences may enable differential binding of regulatory proteins to HIF-la and HIF-2a. HIF-3a is more markedly different from the other two HIF-a isoforms as it apparently has no functional NODD domain, and only the CODD domain within the N-terminal TAD has been identified. Additionally, HIF-3a lacks the C-TAD that exists in both HIF-la and HIF-2a. (28). Relatively little is known about the importance of HIF-3a as compared with the intensively investigated HIF-l/2a isoforms. 

Figure 23,7 The dimeric, oxygen bridged, lMo204-(C204)2(H20)2] showing the close approach of ihe 2 Mo atoms and unusually large range of Mo-0 distances from 165 to 222 pm.

Dimers oxygen compounds Pyridines Nonactive Nonactive Nonactive... 

Gouy probably dimeric, oxygen-bridged antiferromagnetism ... 

CTD.ORINE OXYGEN ACIDS AND SALTS - DICTD.ORINE MONOXIDE, HYPOCTD.OROUS ACID, AND HYPOCm ORITES] (Vol 5) Alkylketene dimers (AKD)... 

A typical oxidation is conducted at 700°C (113). Methyl radicals generated on the surface are effectively injected into the vapor space before further reaction occurs (114). Under these conditions, methyl radicals are not very reactive with oxygen and tend to dimerize. Ethane and its oxidation product ethylene can be produced in good efficiencies but maximum yield is limited to ca 20%. This limitation is imposed by the susceptibiUty of the intermediates to further oxidation (see Figs. 2 and 3). A conservative estimate of the lower limit of the oxidation rate constant ratio for ethane and ethylene with respect to methane is one, and the ratio for methanol may be at least 20 (115). 

Bond dissociation energies (BDEs) for the oxygen—oxygen and oxygen— hydrogen bonds are 167—184 kj/mol (40.0—44.0 kcal/mol) and 375 kj/mol (89.6 kcal/mol), respectively (10,45). Heats of formation, entropies, andheat capacities of hydroperoxides have been summarized (9). Hydroperoxides exist as hydrogen-bonded dimers in nonpolar solvents and readily form hydrogen-bonded associations with ethers, alcohols, amines, ketones, sulfoxides, and carboxyhc acids (46). Other physical properties of hydroperoxides have been reported (46). 

The a-oxygen-substituted hydroperoxides and dialkyl peroxides comprise a great variety as shown in Figure 1. When discussing peroxides derived from ketones and hydrogen peroxide, (1) is often referred to as a ketone peroxide monomer and (2) as a ketone peroxide dimer. 

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