Alcohols 540 ALKALI METAL IONS

The method of Gaver147 for nonreducing carbohydrates (refluxing the carbohydrate in alcoholic alkali metal hydroxide solution without concomitant azeotropic distillation) might give results similar to those obtained by the Wolfrom method.8 -" However, the presence of water and hydroxide ion in the final reaction mixture would probably cause a. small fraction of the product to be the hydroxide adduct. 

The trapped electrons were formed simply by depositing alkali metal atoms on ice or solid alcohols at 77°K. Studies were made of the reactions between sodium or potassium atoms and ice (HgO or D2O), methanol, ethanol, isopropyl alcohol, t-butyl alcohol or dodecanol. The reactions of caesium, rubidium and lithium with ice were also investigated. The deposits were highly coloured and the optical and e.s.r. spectra showed that the electron was no longer associated with the alkali metal ion but had been transferred completely to the solid matrix. 

Analytical chemistry of the alkalis is difficult. There are a few complex reagents that will precipitate with ions like Na+ and K+, but the reactions are best done using ether or alcohol as the solvent in place of water. It is more common to detect the presence of alkali metals in solutions or compounds by the characteristic colors the alkali metal ions impart to flames. In descending order, lithium salts give a carmine color, sodium salts a yellow color, potassium a violet color, rubidium a bluish red color, and cesium a blue color. 

There has been considerable recent interest in the reductions of [Fe(CN)6]. The electron exchange with A -propyl-l,4-dihydronicotinamide is catalyzed by alkali metal ions. The increase in reaction rate is attributed to the polarizability of M and the observed linear free energy relationship is discussed. An outer-sphere mechanism is postulated in the oxidation of phenothiazines. A free radical mechanism involving the alcohol anion is invoked in the reaction of 1-and 2-propanol in aqueous alkaline media, the kinetic order being unity for [Fe(CN)6], OH, and alcohol concentrations. Catalysis by metal ions has also been observed in the presence of copper(II) and ruthenium(III) complexes. In the oxidation of a-hydroxypropionic acid in alkaline media,a Cu(II)-ligand complex is formed which is oxidized slowly to a copper(III) species. Alkaline ferricyanide oxidizes butanol, the process being catalyzed by chlororuthenium complexes.The rate law is consistent with oxidation of the alcohol by the Ru(III) followed by reoxidation of the catalyst by [Fe(CN)6]. The rate law is of the form ... 

The alkali metal tetrahydridoborates are salts those of sodium and potassium are stable in aqueous solution, but yield hydrogen in the presence of a catalyst. They are excellent reducing agents, reducing for example ion(III) to iron(II). and silver ions to the metal their reducing power is used in organic chemistry, for example to reduce aldehydes to alcohols. They can undergo metathetic reactions to produce other borohydrides, for example... 

A competing reaction in any Birch reduction is reaction of the alkali metal with the proton donor. The more acidic the proton donor, the more rapid IS the rate of this side reaction. Alcohols possess the optimum degree of acidity (pKa ca. 16-19) for use in Birch reductions and react sufficiently slowly with alkali metals in ammonia so that efficient reductions are possible with them. Eastham has studied the kinetics of reaction of ethanol with lithium and sodium in ammonia and found that the reaction is initially rapid, but it slows up markedly as the concentration of alkoxide ion in the mixture... 

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