Ethylene oxide thermodynamic properties

Recent investigations have shed light on peculiarities of the NOS action mechanism the role of the H4B cofactor and CaM, and cooperativity in kinetic and thermodynamic properties of different components of the nitric oxide synthesis system. Stop flow experiments with eNOS (Abu-Soud et al., 2000) showed that calmodulin binding caused an increase in NADH-dependent flavin reduction from 0.13 to 86 s 1 at 10 °C. Under such conditions, in the presence of Arg, heme is reduced very slowly (0.005 s 1). Heme complex formation requires a relatively high concentration ofNO (>50 nM) and inhibits the entire process NADH oxidation and citrulline synthesis decreases 3-fold and Km increases 3-fold. NOS reactions were monitored at subzero temperatures in the presence of 50% ethylene glycol as an anti-freeze solvent (Bee et al., 1998). 

A characteristic property of surfactant molecules is their tendeney to aggregate at interfaces. Examples are adsorptions onto solids and monolayer formation at an air-water interface. Surfactants sometimes ereate their own interface by forming very small aggregates like mieelles or vesieles to remove a portion of their structure from direct contact with a solvent. In ease of a mieelle formed with a surfactant such as Triton X-IOO, the hydroearbon ehains are in closer contact in the center and form a hydrophobic microenvironment. The ethylene oxide moieties are exposed to water with mueh greater frequeney. If a hydrophobic species is added into this micellar system, there will be a tendeney for the hydrophobic molecules to be concentrated inside a mieelle. At low concentration, the micelle system and the added hydrophobic additives ean reach a thermodynamic equilibrium, which is often called microemulsion system. At high concentration, the hydrophobic additives form their own separate phase and the surfactant molecules serve only as a decorative layer... 

SAD Sadeghi, R., Hosseini, R., and Jamebbozoig, B., Effect of sodium phosphate salts on the thermodynamic properties of aqueous solutions of poly(ethylene oxide) 6000 at different temperatures, J. Chem. Thermo(fyn., 40, 1364, 2008. 

From one to four units of ethylene oxide have been used to space a group with liquid crystalline properties, methoxybiphenyl, different distances from a methacrylate group (34). Hydrodynamic and thermodynamic properties were calculated. 

Examples of synergistic effects are now very numerous in catalysis. We shall restrict ourselves to metallic oxide-type catalysts for selective (amm)oxidation and oxidative dehydrogenation of hydrocarbons, and to supported metals, in the case of the three-way catalysts for abatement of automotive pollutants. A complementary example can be found with Ziegler-Natta polymerization of ethylene on transition metal chlorides [1]. To our opinion, an actual synergistic effect can be claimed only when the following conditions are filled (i), when the catalytic system is, thermodynamically speaking, biphasic (or multiphasic), (ii), when the catalytic properties are drastically enhanced for a particular composition, while they are (comparatively) poor for each single component. Therefore, neither promotors in solid solution in the main phase nor solid solutions themselves are directly concerned. Multicomponent catalysts, as the well known multimetallic molybdates used in ammoxidation of propene to acrylonitrile [2, 3], and supported oxide-type catalysts [4-10], provide the most numerous cases to be considered. Supported monolayer catalysts now widely used in selective oxidation can be considered as the limit of a two-phase system. 

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