Active hydrogen, definition

Most of the classes in Table 15-4 are self-explanatory, but some can use additional definition. Class 4 includes halogenated solvents that have highly active hydrogens as described by Ewell, Harrison, and Berg [Ind. Eng. Chem., 36, 871 (1944)]. These are molecules that... 

Solvents. Some polyurethane coatings are solvented. Polyurethane prepolymer solutions are also supplied as solutions in organic solvents. Polyurethane-grade solvents by definition must have a low content of active hydrogens therefore, alcohols and amines, etc. are not suitable, nor are other solvents containing more than 0.5% water. 

The acidity of aqueous solutions is often expressed in a logarithmic scale of the hydrogen ion activity. The definition of pH as ... 

Furthermore although there is no definite evidence, the oxidative additions of active hydrogen compounds, such as alcohols, water, hydrogen cyanide, and active methylene compounds, are reasonably predictable from their reactivity. Some reactions involving these compounds can be explained by oxidative addition with splitting of bonds to hydrogen. Several examples of this type are surveyed later. 

Just taking a quick look at the different chapters, one can realize which areas of each field are mature and which can evolve immediately. Although it is very difficult to venture a general trend for the whole area, we could emphasize that there is not a tmly enantioselective version for the mono-activated hydrogen autotransfer reaction. The use of first-row transition metals is almost an unexplored Blue Ocean , in all aspects. Furthermore, the possible impact of green neoteric solvents, including deep eutectic mixtures, supercritical fluids, and bio-based solvents, on the hydrogen transfer process is definitely unknown. 

Hydrogen Electrode an electrode at which the equilibrium (aq.) + jHj, is established. By definition, at unit activity of hydrogen ions and unit fugacity of hydrogen gas the potential of the standard hydrogen electrode h+/y//2 =... 

In addition to actual synthesis tests, fresh and used catalysts were investigated extensively in order to determine the effect of steam on catalyst activity and catalyst stability. This was done by measurement of surface areas. Whereas the Brunauer-Emmett-Teller (BET) area (4) is a measure of the total surface area, the volume of chemisorbed hydrogen is a measure only of the exposed metallic nickel area and therefore should be a truer measure of the catalytically active area. The H2 chemisorption measurement data are summarized in Table III. For fresh reduced catalyst, activity was equivalent to 11.2 ml/g. When this reduced catalyst was treated with a mixture of hydrogen and steam, it lost 27% of its activity. This activity loss is definitely caused by steam since a... 

On the basis of this definition, one can determine, for instance, the activity of electrolytic solutions in terms of the real hydrogen ion activity. Rybkin et al. found that the Ax effect may be stabilized by adding surface-active substances in small quantities to the solution. Ac-... 

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