Metallic hydrogen

B1.29.6 HIGH-PRESSURE FORMS OF FAMILIAR OR USEFUL MATERIALS DIAMOND, FLUID METALLIC HYDROGEN, METALLIC OXYGEN, IONIC CARBON DIOXIDE, GALLIUM NITRIDE... 

If all these holes were filled, the hydrogen-metal ratio would be a definite and fixed number in practice, this rarely happens, and... 

Two types of hydrogen replacement are discussed here (1) the base-induced hydrogen-deuterium exchange reactions and (2) the hydrogen-metal exchange reactions. 

Under the action of strong organometallic bases, thiazole undergoes hydrogen-metal interconversion. Ethylmagnesium bromide reacts at 0°C with thiazole in ether to form an insoluble adduct that upon heating evolves ethane almost quantitatively and affords an etheral solution of thiazol-2-ylmagnesium bromide (155) (12). Proof of the structure of this... 

In conclusion, it appears that in neutral or weakly acidic conditions only the methyl in the 2-position shows pseudoacidic behavior. The same conclusion can be drawn from the base-induced hydrogen-metal exchange reactions discussed in Section III.5.B. 

Phthalocyanines 2 can be made from metal-free phthalocyanines 1 by hydrogen/metal exchange. 

An example of hydrogen/metal exchange has been reported for 1,6,10,15,19,24,28,33-octasub-stituted 2,3-naphthalocyanine 7. 

Cobalt may be introduced via hydrogen/metal exchange into a metal-free 1,4,8,11,15,18,22,25-octaazaphthalocyanine 3. 

In addition to the surface physics and chemistry phenomena involved, a further effect may follow the interaction at the hydrogen-metal surface, that is the absorption of hydrogen by the bulk phase of the metal. This absorption leads to the formation of a solid solution within a certain, usually low, range of hydrogen concentrations. However, with several transition metals, exceeding a certain limit of hydrogen concentration results in the formation of a specific crystallographically distinct phase of the... 

Extensive studies are still needed on hydrogen-metal surface interactions, leading to various forms of adsorbed hydrogen of different specific reactivity with the metal catalyst surface. Nevertheless, one can conclude on the basis of the experimental evidence presented that certain facts al-... 

The reactions in this chapter are arranged in order of leaving group hydrogen, metals, halogen, and carbon. Electrophilic substitutions at a nitrogen atom are treated last. 

Such compounds can also be prepared by hydrogen-metal exchange, for example," ... 

However, for the heavier resides, zeolite pore structure may preclude their use in HCK. We have introduce the effect of the pore size and distribution on the conversion and coke formation of asphaltene containing feeds (Section 5.2.1), but we should also point out that they also affect the dispersion of the hydrogenation metals on the catalyst surface. A poor dispersion will also lead to poor hydrogenation and indirectly favor coke formation. 

Comments on the crystal structures of typical hydrogen-metal phases. 

Table 5.2. Structures of a few selected hydrogen-metal compounds. The formulae very often have only an indicative character. Solid solution ranges are frequently observed.

Four different methods to store hydrogen are currently available compressed gas, liquid hydrogen, metal hydrides and sorption on different porous materials (carbon materials, zeolites, metal organic frameworks, etc).2-4... 

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