Highlights of Hydrogen Chemistry

Beyond the enormous impact of hydrogen bonding on physical properties that we already discussed in Chapters 12 and 13, elemental hydrogen is very reactive, combining with nearly every other element to form ionic or covalent hydrides. 

Ionic (Saltlike) Hydrides With very reactive metals, such as those in Group 1A(1) and the larger members of Group 2A(2) (Ca, Sr, and Ba), hydrogen forms saltlike 

The H ion is also a strong reducing agent, as in this example  

Covalent (Molecular) Hydrides Hydrogen reacts with nonmetals to form many covalent hydrides. In most of them, hydrogen has an oxidation number of +1 because the other nonmetal has a higher electronegativity. 

Conditions for preparing covalent hydrides depend on the reactivity of the other nonmetal. For example, with stable, triple-bonded N2, the reaction needs high temperatures ( 400°C), high pressures (—250 atm), and a catalyst  

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Where Hydrogen Fits in the Periodic Table Highlights of Hydrogen Chemistry... 

The synthetic utility of this chemistry was highlighted by short syntheses of various biologically interesting tropanes (Scheme 36). T vo natural products, ferruginine (98) and anhydroecgonine methyl ester (99), have been prepared by selectively hydrogenating the appropriate [3+4] aimulation product followed by ]V-deprotection and iV-methylation. A number of 4P-aryl-3p-propanoyl tropanes, such... 

Three pathways for the ruthenium-catalyzed hydrogenations of ketones, aldehydes, and a,(3-unsaturated aldehydes with several catalyst systems were studied the direct insertion, the migratory insertion, and the concerted hydrogen transfer highlighting the catalyst/substrate configurations that lead to stereoselective differentiation. The contribution of computational chemistry were essential to differentiate these mechanisms of ruthenium-catalyzed reactions and to rationalize the experimentally observed stereochemical outcome. 

Carboneau, M. L. Highlights of the OECD Loft LP-FP-2 experiment including hydrogen generation, fission product chemistry, and transient fission product release fractions. Proc. Open Forum The OECD Loft Project Achievements and Significant Results. Madrid, Spain, 1990, p. 261-284... 

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