Regeneration reaction, alkali metal

Table II. Inorganic Reaction - Alkali Metal Fluoride Regeneration MCl(s) +HF(g) <=> MF(s) + HCl(g)...

The reaction involves the transfer of an electron from the alkali metal to naphthalene. The radical nature of the anion-radical has been established from electron spin resonance spectroscopy and the carbanion nature by their reaction with carbon dioxide to form the carboxylic acid derivative. The equilibrium in Eq. 5-65 depends on the electron affinity of the hydrocarbon and the donor properties of the solvent. Biphenyl is less useful than naphthalene since its equilibrium is far less toward the anion-radical than for naphthalene. Anthracene is also less useful even though it easily forms the anion-radical. The anthracene anion-radical is too stable to initiate polymerization. Polar solvents are needed to stabilize the anion-radical, primarily via solvation of the cation. Sodium naphthalene is formed quantitatively in tetrahy-drofuran (THF), but dilution with hydrocarbons results in precipitation of sodium and regeneration of naphthalene. For the less electropositive alkaline-earth metals, an even more polar solent than THF [e.g., hexamethylphosphoramide (HMPA)] is needed. 

We have recently reported a new photochemical reaction, in which faded alkali metal solutions in ethylamine are regenerated by UV ir-... 

The use of water, which has strong OH-bonds, should eliminate hydrogen abstraction from the matrix. However, the yield of cyclohexane was still higher than that of cyclohexene. This result can be attributed to the formation of hydrogen atoms by reaction of some alkali metal atoms with water instead of with cyclohexyl bromide. These hydrogen atoms could then either combine with cyclohexyl radicals to give cyclohexane or add to cyclohexene (formed from a previous disproportionation reaction) to regenerate cyclohexyl radicals. 

Miscellaneous Reactions. Sodium bisulfite adds to acetaldehyde to form a white crystalline addition compound, insoluble in ethyl alcohol and ether. This bisulfite addition compound is frequently used to isolate and purify acetaldehyde, which may be regenerated with dilute acid. Hydrocyanic acid adds to acetaldehyde in the presence of an alkali catalyst to form cyanohydrin the cyanohydrin may also be prepared from sodium cyanide and the bisulfite addition compound. Acrylonitrile [107-13-1] (qv) can be made from acetaldehyde and hydrocyanic acid by heating the cyanohydrin that is formed to 600—700°C (77). Alanine [302-72-7] can be prepared by the reaction of an ammonium salt and an alkali metal cyanide with acetaldehyde this is a general method for the preparation of a-amino acids called the Strecker amino acids synthesis. Giignard reagents add readily to acetaldehyde, the final product being a secondary alcohol. Thioacetaldehyde [2765-04-0] is formed by reaction of acetaldehyde with hydrogen sulfide thioacetaldehyde polymerizes readily to the trimer. 

Trimethylsilyl groups at triple bonds are easily removed by mild bases such as alkali metal carbonates to yield 35 with a terminal triple bond. The following reaction is a Pd-catalyzed reductive addition of tributyl stannane, HSnBu3, to the triple bond, which forms the -configured vinyl stannane 19. One possible rationalization of the outcome is the mechanism shown below First, the catalytically active species 36 inserts into the tin-hydrogen bond to form 37. Then, cis addition takes place after coordination to the alkyne triple bond, generating species 39. Reductive elimination affords the vinyl stannane 19 and regenerates the catalyst 36. ... 

It was proposed that a Lewis acid lanthanum center controls the direction of the carbonyl function and activates the enone while the sodium alkoxide forms enolate intermediates and regenerates the catalyst by hydrogen abstraction (Scheme 6). Other Ln/alkali metal combinations, including La/Li, show negligible asymmetric induction, yet give almost racemic products in excellent yield. In contrast, alkali-metal free BINOL ester enolate complexes catalyze Michael reactions with high enantioselectivities, albeit at lower temperatures. 

For continuous regeneration of the suppressor, either potassium hydroxide with a concentration of c = 0.04 mol/L or tetramethylammonium hydroxide with a concentration of c = 0.02 mol/L may be used. The choice of regenerent depends on the type of analyte. Potassium hydroxide is recommended as a regenerent for the analysis of alkali metals. If ammonium is also to be analyzed, it should be noted that the linear range for the determination of this ion is very small when using potassium hydroxide as the regenerent. This is caused by the equilibrium between NH4OH as the suppressor reaction product and the free base NH3. 

A weakly acidic electrolyte is preferable, which is achieved by neutralizing the electrolyte to an extent of 2 to 10% by an alkali metal hydroxide or alkoxide. This allows the use of an undivided cell, because hydrogen discharge, which continuously regenerates carboxylate that is consumed at the anode, is the exclusive cathode reaction. The endpoint of the electrolysis is indicated by the change of the electrolyte to an alkaline pH. 

PMMA cross-linked by ethylene dimethacrylate with immobilized side oligooxy-ethylene chains were used as interfacial transfer catalysts [80]. Also studied was the formation of benzyl acetate, benzyl bromide and alkali metal acetates in boiling chloroform and of n-octylphenyl ester from n-octyl iodide and K or Na phenoxide in toluene at 100 °C in the presence of a catalytic polymer amount. The product yield increased with an increase in the reaction time and the catalyst/acetate or catalyst/ phenoxide molar ratio. The conversion of benzyl bromide increased according to the following sequence of acetates Napolymeric catalyst could be regenerated and used many times. 

In the presence of water, Wacker cheudstiy tends to predominate, whereby ethylene reacts with water rather than acetic acid and forms acetaldehyde as the primary product. Heniy and Pandeyl l showed that the addition of alkali metal acetates can help to shift the product spectrum in order to form vinyl acetate in higher yields. The reaction is thought to involve the nucleophillic attack of ethylene by acetate to form a C2H4-OAC-Pd complex which subsequently undergoes /3-C-H activation to form VAM. Acetic acid or HCl can desorb from the complex to form Pd ° which is reoxidized back to copper chloride to regenerate Pd2+. 

For the inorganic regeneration reaction (eq 3) the situation is not so clear. Nowhere in the literature is it documented which alkali metal chloride can be most easily or efficiently converted to the corresponding alkali metal fluoride. A similar thermodynamic analysis for this reaction as shown in Table II 8,11) indicates a preference for the smaller cation. This is in contrast to the requirement of the organic... 

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