Add-base properties

Adsorption of third particles other than water molecules on metal electrodes influences the microstructure and the electrochemical activity of the electrode interface. For example, the interface of metal electrodes usually acts as a Lewis add in the adsorption of water molecules, but its Lewis add-base property is altered by the adsorption of third partides. Electronegative particles such as oi en molecules, if adsorbed, increase the local Lewis acidity of interfacial metal atoms around the adsorption sites whereas, electropositive particles such as sodium atoms, if adsorbed, increase the local Lewis basicity around their adsorption sites. Furthermore, the adsorption energy of water molecules is altered by the coadsorption of third partides on metal electrodes. 

Paukshtis, E.A. and Yurchenko, E.N. (1983) Study of the add-base properties of heterogeneous catalysts by infrared spectroscopy. Russ. Chem. Rev, 52, 242-258. 

Oxides of transition metals exhibit more complex add-base properties that may depend on the oxidation number of the metal. 

Bautista, F.M., Campelo, ).M Garda, A., Luna, D., Marinas, ).M., Quiros, R.A., Romero, A.A., Influence of add-base properties of catalysts in the gas-phase dehydration-dehydrogenation of cyclohexanol, Appl. Catal, 243, 92-107, 2003... 

Bronsted-Lowry Theory of Acids and Bases Conjugate Acids and Bases Add-Base Properties of Water... 

A sr filtration, washing and drying at 390 K, all the solids were calcined at 923 K for 3 h. Details on the characterization of all catalysts have been previously described [13,16,17]. The surface area 83 and add-base properties, measured by a spedrophotometric method, are collected in Table 1. 

Another field of investigation is the use of metal nitridooxophosphates such as AlPON (11) or ZrPON (12) as catalysts. The incorporation of nitrogen leads to a change in add-base properties and to improved stability. 

Manipulation of Stationary-Phase Add-Base Properties by a Surface-Buffering Effect... 

The success of XPS lies in its surface specificity (analysis depth of ca. 5 mn), low degree of degradation of tested materials, quantitative aspect, and detection of all elements (except hydrogen) and their chemical shifts. The so-called chemical shift is the cornerstone of XPS since it enables the surface scientist to study chemical bonding and to derive materials properties such as refractive indices of thin optical layers [150], the nondispersive component of the surface energy of polymers [151] and the add base properties of alcohols and amines [152]. 

Lopez et al. [160] applied the technique of Fermi level shift monitoring to characterize the add base properties of passive films on aluminum. The decreasing trend of relative basicity was found to be boehmite > thermal oxide > NaOH-degreased surface > silicate containing detergent-degreased surface > phosphoric add anodic film. The... 

Formation of such unstable intermediates changes proton transfer between reactants and the solvent water (pX 14, pX 0) from being thermodynamically unfavourable to favourable. Catalysis can increase the rate of reaction by either (i) trapping such intermediates, (ii) stabilising the intermediate and the transition states leading to them, and (iii) providing an alternative mechanism not requiring the formation of such unstable intermediates. The mechanism of catalysis of many of these types of reactions is enforced by the lifetime and add-base properties of the initially formed intermediate [3]. 

The add-base properties of many natural products are important for their isolation, distribution in the body, and therapeutic effects. For example, morphine (page 2) is isolated from the opium poppy and crosses into the brain as the free base, where the nitrogen is not charged. However, it exerts its pain-relieving effects as the charged species. 

Belgacem M.N., Gandini A., Inverse gas chromatography as a tool to chtnacterize dispersive and add base properties of the surface of fibers and powders Chapter 2, in Interfacial Phenomena in Chromatography (Ed. Pefferkom E.), Marcel Dekker, Inc., New York, 1999. 

Example 15.14 illustrates how to predict the add-base properties of salt solutions. 

ICjC measures the retention times of the probe molecules in the column. Molecules with a high adsorption enthalpy will take longer to pass through the column than molecules with a low adsorption enthalpy. If probe molecules of varying acid-base character are used, the add-base properties of the fiber can be determined. This technique has also been used to determine the surface area of carbon fibers by using nonpolar probe molecules [61]. 

Mononuclear metal carbonyls or small metal carbonyl dusters introduced into zeolite supercages, either by sorption or chemical vapor deposition, may react to form metal carbonyl clusters having nudearities (numbers of metal atoms) greater than those of the precursors. The resultant metal carbonyl dusters can be neutral or anionic, depending on the add-base properties and the degree of hydration of the zeolite. 

When a substance is dissolved in water, it may behave as an acid, behave as a base, or exhibit no add-base properties. How does the chemical structure of a substance determine which of these behaviors is exhibited by the substance For example, why do some substances that contain OH groups behave as bases, releasing OH ions into solution, whereas others behave as adds, ionizing to release H ions Why are some adds stronger than others In this section we will discuss briefly the effects of chemical structure on acid-base behavior. 

The dissolution of NiO has been correlated to the add/base properties of the molten carbonate. 

So far we have discussed add-base properties in terms of the Brpnsted theory. For example, a Br0nsted base is a substance that must be able to accept protons. By this definition, both the hydroxide ion and ammonia are bases ... 

Another quantity that characterizes the add-base properties of protic and proto-genic solvents, SH, is their autoprotolysis constant. This is the equilibrium constant... 

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