Thermal decarboxylation metal

Attempted syntheses of trifluoromethyl derivatives of germanium, tin, and lead by thermal decarboxylation either resulted in decomposition of the trifluoroacetate without forming carbon dioxide (22,39,40) or gave carbon dioxide but no trifluoromethyl organometallic (22). In the latter case, the metal fluoride was detected. This suggests that the trifluoromethyl compound is thermally unstable and decomposes by fluoride abstraction. 

Syntheses of aryl organometallics other than polyhalogenoaryls by thermal decarboxylation are comparatively rare. There are several reasons for this. For transition elements, the thermal stability of simple aryls is often low, especially by comparison with polyhalogenoaryl derivatives, thereby excluding syntheses at elevated temperatures. Electron-withdrawing substituents frequently aid thermal decarboxylation (Section III,A-D), and their absence inhibits major mechanistic paths to both transition metal and main group element derivatives, e.g., SEi (carbanionic) and oxidative addition (Section II). In thermal decomposition of... 

Successful thermal decarboxylation of metal arenoates other than poly-halogenoarenoates are restricted to mercury compounds and fall into three categories, namely (i) those where electron-withdrawing substituents other than halogens are present in the organic groups, (ii) those where substituents and/or conditions are used which favor a different mechanism, e.g., classic electrophilic aromatic substitution, or (iii) those where the conditions are sufficiently forcing for both mercuration and decarboxylation to occur. 

A reaction mechanism with Fe304 as catalyst has been proposed [68], in agreement with previous work concerning decarboxylation of acids in the presence of a metal oxide [83]. After the transient formation of iron(II) and iron(III) carboxylates from the diacid and Fe304 (with elimination of water), the thermal decarboxylation of these salts should give the cyclic ketone and regeneration of the catalyst. 

The thermal decarboxylation of acids over a metal oxide catalyst (Expts 5.92 and 5.93). 

Several examples of the synthesis of aryl alkyl ketones by the thermal decarboxylation of mixtures of carboxylic acids over heated metal salts are included under the preparation of aliphatic ketones (Expt 5.93). In this section the preparation of dibenzyl ketone (Expt 6.127) by the pyrolysis of the barium salt of phenylacetic acid, which proceeds in good yield, is included as a further example of this general type of synthesis. 

THE THERMAL DECARBOXYLATION OF ACIDS OVER A METAL OXIDE CATALYST... 

The thermal decarboxylation of a mixture of barium salts has been used to prepare unsymmetrical ketones the yields are not stated. The earlier procedure has been modified by carrying out the reaction in vacuo in an iron flask. Glass reaction vessels are inferior. In this manner, a large number of the high-molecular-weight methyl ketone s, C9, C,o, C,j-C , and C, are prepared in 54-67% yields. Cyclopentanone has been synthesized in 80% yield by distillation of adipic acid from barium hydroxide at 295°. In a study of metallic oxides and carbonates, magnesium oxide is preferred for the liquid-phase ketonization of stearic acid at 330-360° (95%). A convenient method for the preparation of dibenzyl ketone is the reaction of phenylacetic acid, acetic anhydride. 

Decarboxylation of silver carboxylates is a well known thermal process and is involved in the Hunsdiecker76 or Kolbe77 reactions. The Hunsdiecker reaction is the thermal decarboxylation of silver salts of acids and is used for the formation of bromoalkanes and related compounds, while the Kolbe process involves electrolysis of carboxylates as a route to decarboxylated radicals that can dimerize. Silver carboxylates are also photochemically reactive and the irradiation has been described as a facile process for the formation of alkyl radicals, as illustrated in equation 678. Later experimentation has shown that the irradiation of silver trifluoroacetate can serve as a route to trifluoromethyl radicals. This development uses irradiation of silver trifluoroacetate in the presence of titanium dioxide as a photocatalyst. The reaction follows the usual path with the formation of metallic silver and the formation of radicals. However, in this instance the formation of metallic... 

Drummond SE, Palmer DA (1986) Thermal decarboxylation of acetate, part II. Boundary conditions for the role of acetate in the primary migration of natural gas and the transportation of metals in hydrothermal systems. Geochim Cosmochim Acta 50 825-833... 

Nazar AFM, Wells CF (1985) Kinetics of the oxidation of substrate ligands by transition-metal cations. J Chem Soc Faraday Trans I, 81 801-812 Nef JU (1901) Dissoziationsvorgange bei den einatomigen Alkoholen, Aethern und Salzen. Justus Liebigs Ann Chem 318 220-226 Palmer DA, Drummond SE (1986) Thermal decarboxylation of acetate. Part I. The kinetics and mechanism of reaction in aqueous solution. Geochim Cosmochim Acta 50 813-823... 

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