Hydrogen with alkali metals

Numerous organic syntheses are based on stoichiometric oxidations of hydrocarbons with sodium dichromate and potassium permanganate, or on hydrogenations with alkali metals, borohydrides or metallic zinc. In addition, there are reactions... 

Compare hydrogen with alkali metals and halogens, and distinguish saltlike from covalent hydrides ( 14.1) (EPs 14.1-14.5)... 

Sodium rubidium carbonate-butylamine Ring hydrogenation with alkali metal catalysts... 

Interactions of molecular hydrogen with alkali metal halides in argon matrices A computational model "... 

The simplest case arises when the electronic motion can be considered in temis of just one electron for example, in hydrogen or alkali metal atoms. That electron will have various values of orbital angular momentum described by a quantum number /. It also has a spin angular momentum described by a spin quantum number s of d, and a total angular momentum which is the vector sum of orbital and spin parts with... 

The Birch reductions of C C double bonds with alkali metals in liquid ammonia or amines obey other rules than do the catalytic hydrogenations (D. Caine, 1976). In these reactions regio- and stereoselectivities are mainly determined by the stabilities of the intermediate carbanions. If one reduces, for example, the a, -unsaturated decalone below with lithium, a dianion is formed, whereof three different conformations (A), (B), and (C) are conceivable. Conformation (A) is the most stable, because repulsion disfavors the cis-decalin system (B) and in (C) the conjugation of the dianion is interrupted. Thus, protonation yields the trans-decalone system (G. Stork, 1964B). 

Single-bond cleavage with molecular hydrogen is termed hydrogenolysis. Palladium is the best catalyst for this purpose, platinum is not useful. Desulfurizations are most efficiently per-formed with Raney nickel (with or without hydrogen G.R. Pettit, 1962 A or with alkali metals in liquid ammonia or amines. The scheme below summarizes some classes of compounds most susceptible to hydrogenolysis. 

In the sodium atom pairs of 3/2 states result from the promotion of the 3s valence electron to any np orbital with n > 2. It is convenient to label the states with this value of n, as n P 1/2 and n f 3/2, the n label being helpful for states that arise when only one electron is promoted and the unpromoted electrons are either in filled orbitals or in an x orbital. The n label can be used, therefore, for hydrogen, the alkali metals, helium and the alkaline earths. In other atoms it is usual to precede the state symbols by the configuration of the electrons in unfilled orbitals, as in the 2p3p state of carbon. 

Base catalysis is most effective with alkali metals dispersed on solid supports or, in the homogeneous form, as aldoxides, amides, and so on. Small amounts of promoters form organoalkali comnpounds that really contribute the catalytic power. Basic ion exchange resins also are usebil. Base-catalyzed processes include isomerization and oligomerization of olefins, reactions of olefins with aromatics, and hydrogenation of polynuclear aromatics. 

Hydrides — True hydrides (i.e., those in which the hydrogen is in its anionic or most reduced form) are salt-like compounds in which the hydrogen is combined with alkali metals, either alone as simple hydrides or in association with other elements as complex hydrides. Hydrides react with water to release hydrogen. 

The reduction of porphycenes, e.g. 1, can be achieved by catalytic hydrogenation22-25 or chemical reduction with alkali metals.22 With alkali metals one of the C —C double bond bridges in 1 is reduced to yield a 19,20-dihydroporphycene2. On catalytic hydrogenation of porphycene (1), 2,3-dihydro porphycene (3) is formed which can be compared to chlorin, the dihydrogenated form of porphyrin. 

No binary hydrides have been characterized, but reactions of the metal powders with alkali metal hydrides in a hydrogen atmosphere lead to Li3RhH4 (planar RhH4 ) and M3MH6 (M = Li, Na M = Rh, Ir) with octahedral MHj [34],... 

Diesters of phosphorous acid are in general neutral because the phosphorous acid exists mostly in the phosphonate form with one hydrogen directly attached to the phosphorus. But with alkali metals the H can be changed against the alkali and reactive intermediates formed. Such alkali metal derivatives of dialkyl phosphites react with alkyl halides to give dialkyl alkanephosphonates, according to Eqs. (45) and (46). 

Triple bonds can also be selectively reduced to double bonds with DIBAL-H, " with activated zinc (see 12-36), with hydrogen and Bi2B-borohydride exchange resin, ° or (internal triple bonds only) with alkali metals (Na, Li) in liquid ammonia or a low-molecular-weight amine.Terminal alkynes are not reduced by the Na—NH3 procedure because they are converted to acetylide ions under these conditions. However, terminal triple bonds can be reduced to double bonds by the... 

Te(OH) forms adducts with alkali-metal fluorides such as Te(OH) -NaF or Te(OH)8-2KF (102). Single-crystal X-ray diffraction shows that, contrary to the earlier assumption, there is no direct bonding of fluorine to tellurium. The fluoride ions are incorporated into the structure by short O—H F hydrogen bonds (6, 7). 

The polyhedral boranes and carboranes discussed above may be regarded as boron clusters in which the single external orbital of each vertex atom helps to bind an external hydrogen or other monovalent atom or group. Post-transition main group elements are known to form clusters without external ligands bound to the vertex atoms. Such species are called bare metal clusters for convenience. Anionic bare metal clusters were first observed by Zintl and co-workers in the 1930s [2-5], The first evidence for anionic clusters of post-transition metals such as tin, lead, antimony, and bismuth was obtained by potentiometric titrations with alkali metals in liquid ammonia. Consequently, such anionic post-transition metal clusters are often called Zintl phases. 

With hydrogen, the alkali metals form the mono-hydrides MeH, having salt-like properties and a partially ionic, Me H, NaCl-type structure. They are colourless crystalline solids having a fairly negative AH of formation. The mono-hydrides react with water. They may be prepared from hydrogen and the metal (heated at 700-800°C for Li, 350-400°C for the others) or through the reaction of hydrogen with the alkali mono-oxide, nitride, etc. 

The FAB plasma provides conditions that allow to ionize molecules by either loss or addition of an electron to form positive molecular ions, M" , [52,89] or negative molecular ions, M, respectively. Alternatively, protonation or deprotonation may result in [Mh-H]" or [M-H] quasimolecular ions. Their occurrence is determined by the respective basicity or acidity of analyte and matrix. Cationization, preferably with alkali metal ions, is also frequently observed. Often, [Mh-H]" ions are accompanied by [MH-Na]" and [Mh-K]" ions as already noted with FD-MS (Chap. 8.5.7). Furthermore, it is not unusual to observe and [Mh-H]" ions in the same FAB spectmm. [52] In case of simple aromatic amines, for example, the peak intensity ratio M 7[Mh-H] increases as the ionization energy of the substrate decreases, whereas 4-substituted benzophenones show preferential formation of [Mh-H]" ions, regardless of the nature of the substituents. [90] It can be assumed that protonation is initiated when the benzophenone carbonyl groups form hydrogen bonds with the matrix. 

Dihydroaromatics find diverse applications. The main way to prepare them is through Birch reduction of aromatic compounds (Birch 1944, Wooster and Godfrey 1937, Hueckel and Bretschneider 1939). Aromatic compounds are hydrogenated in diethyl ether or liquid ammonia, with alkali metals as reductants and alcohols as proton sources. 

The carboxylic acids like alcohols evolve hydrogen with electropositive metals and form salts with alkalies similar to phenols. However, unlike phenols they react with weaker bases such as carbonates and hydrogenearbonates to evolve carbon dioxide. This reaction is used to detect the presenee of carboj rl group in an organie eompound. 

Amino acids and peptides in their compounds with alkali metal salts are in the zwitterion form. The anion is hydrogen bonded to the NHs+... 

Silane reacts with alkali metals dissolved in a solvent such as 1,2-dimethoxyethane to form the metal derivative MSiH3 and hydrogen or metal hydride ... 

Selenides. Selenium forms compounds with most elements. Binary compounds of selenium with 58 metals and 8 nonmetals, and alloys with three other elements have been described (55). Most of the selenides can be prepared by a direct reaction. This reaction varies from very vigorous with alkali metals to sluggish and requiring high temperature with hydrogen. 

Binary Selenides. Most binary selenides are formed by heating selenium in the presence of the element, reduction of selenites or selenates with carbon or hydrogen, and double decomposition of heavy-metal salts in aqueous solution or suspension with a soluble selenide salt, eg, Na2Se or (NH Se [66455-76-3]. Atmospheric oxygen oxidizes the selenides more rapidly than the corresponding sulfides and more slowly than the tellurides. Selenides of the alkali, alkaline-earth metals, and lanthanum elements are water soluble and readily hydrolyzed. Heavy-metal selenides are insoluble in water. Polyselenides form when selenium reacts with alkali metals dissolved in liquid ammonia. Metal (M) hydrogen selenides of the M HSe type are known. Some heavy-metal selenides show important and useful electric, photoelectric, photo-optical, and semiconductor properties. Ferroselenium and nickel selenide are made by sintering a mixture of selenium and metal powder. 

In the synthesis of fluorinated alcohols porous aluminum trifluoride has been found to be an efficient substitute for anhydrous hydrogen fluoride in combination with alkali metal acid fluorides for ring-opening reactions of aliphatic 7-oxabicyclo[4.1.0]heptane fluorohydrins under sonification.47... 

The products of the thermal decomposition of 1,10-phenanthroline have been briefly discussed.370 Exchange of hydrogen for deuterium has been noted with alkali metal complexes of 1,10-phenanthroline. The exchange occurs principally in the 5-position.371,372 A new chemiluminescence reaction arising from the combination of trichloroacetic acid and 4,7-diphenyl-l,10-phenanthroline has been reported.373... 

Reduction. Benzene can be reduced to cyclohexane [110-82-7], C5H12, or cycloolefins. At room temperature and ordinary pressure, benzene, either alone or in hydrocarbon solvents, is quantitatively reduced to cyclohexane with hydrogen and nickel or cobalt (14) catalysts. Catalytic vapor-phase hydrogenation of benzene is readily accomplished at about 200°C with nickel catalysts. Nickel or platinum catalysts are deactivated by the presence of sulfur-containing impurities in the benzene and these metals should only be used with thiophene-free benzene. Catalysts less active and less sensitive to sulfur, such as molybdenum oxide or sulfide, can be used when benzene is contaminated with sulfur-containing impurities. Benzene is reduced to 1,4-cydohexadiene [628-41-1], C6HS, with alkali metals in liquid ammonia solution in the presence of alcohols (15). 

The reaction commences at a temperature above 400° C., before the melting temperature is reached, and the fused product therefore always contains some arsenious oxide.1 When heated in hydrogen, the pentoxide is reduced first to arsenious oxide and then to free arsenic. Similar reduction occurs when it is heated with carbon or phosphorus with sulphur, arsenious sulphide is formed. Arsenic and metallic arsenides result when the pentoxide is heated with alkali metals,2 zinc, lead, iron or most other heavy metals mercury and silver react only at high temperature gold and platinum do not react. 

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