Organometallic compounds with carbon dioxide

Carboxylic acid groups can also be installed in molecules using the reaction of an organometallic compound with carbon dioxide. This is a reductive method since the carbon dioxide is reduced to a carboxylic acid by formation of a new carbon-carbon bond. Both Grignard reagents and organolithium compounds work well in this reaction. 

SCHORIG1N (or Shorygin) REACTION. Organometallic reactions of the Grignard type, employing sodium in place of magnesium the reaction of alkyl sodium compounds with carbon dioxide to give monobasic acids is sometimes known as the Wanklyn reaction. 

This is an excellent reaction for the conversion of most halides to acids containing one additional carbon atom. Carbonation of Grignard reagents and organoalkali compounds gives acids in yields of 50-85%. Ether solutions of the organometallic compounds formerly were treated with carbon dioxide gas at 10° to -10°. A more recent technique involves pouring the solution onto excess crushed Dry Ice. Carbon dioxide... 

A The alkynyl hydrogen of propyne is acidic and hence the propyne will form an organometallic derivative. The Grignard derivative will react with carbon dioxide to give the carboxylic acid. Cis alkenes are formed by the catalytic hydrogenation of alkynes using a Lindlar catalyst. Hence a propynyl alcohol is a precursor to compound (b). This could be obtained by the addition of a propyne anion to propanone ... 

For carboxylations with carbon dioxide reversed-order addition is generally carried out, i.e. the solution or suspension of the metallated compound is poured on the powdered dry ice , which may be covered with an organic solvent. The reason for applying this technique is that alkali salts of carboxylic acids can undergo an attack by the organometallic derivative ... 

Dinjus, E., Fornika, R., Fitter, S., and Zevaco, T. (2002) Carbon dioxide as a Cl building block, in Applied Homogeneous Catalysis with Organometallic Compounds, vol. 3 (eds B. Comils and W.A. Herrmann), 2nd edn, Wiley-VCH Verlag GmbH, Weinheim, pp. 1189-1213. 

With regard to the susceptibility of many organometallics to aerial oxidation, it must be remembered that most compounds containing C-H bonds are thermodynamically unstable with respect to oxidation by molecular oxygen to produce water and carbon dioxide. The mechanisms whereby (for example) many alkyls are spontaneously flammable in air are necessarily difficult to determine the mechanisms involved in the combustion of hydrocarbons are still incompletely understood. Suffice it to say that the kinetic stability of ER to air seems to be low where E is of low electronegativity. 

The reactions of organometallic 20 compounds of transition metals (29) with molecular nitrogen and carbon dioxide... 

The toluene solution of phenylsodium, prepared as described on p. 260, is refluxed for 3 hours. The amount of benzylsodium then present is 0.154 mole, or a yield of 77%. The yield of organometallic compound is determined by pouring the toluene solution onto crushed solid carbon dioxide, treating with dilute hydrochloric acid, and weighing the phenylacetic acid so formed. 

A mixture of 150 ml. of toluene, 11.5 g. (0.5 gram atom) of sodium sand, and 22.5 g. (0.2 mole) of chlorobenzene is stirred at room temperature under an atmosphere of dry nitrogen. After about 45 minutes an exothermic reaction sets in, and the temperature of the reaction mixture is held below 40° with a cooling bath. The entire reaction requires about 2 hours. The toluene solution of phenylsodium should be used immediately. (See preparation of benzylsodium, p. 32.) The yield of organometallic compound is 87%. The yield is determined from the amount of benzoic acid obtained after pouring the above solution on excess crushed solid carbon dioxide followed by acidification. 

More universal is the method of Cp determination using selective tracers such as carbon monoxide and carbon dioxide which interact only with active metal = polymer bondsUsing tagged CO and CO2 as quenching agents systematic data have been accumulated so far on the influence of the composition of catalysts (titanium chlorides with various organometallic compounds) and polymerization conditions on Cp and kp values for the polymerization of ethylene and propylene IS)... 

Since carbon dioxide is a thermodynamically stable, highly oxidized compound, its synthetic utilization requires some kind of a reduction -reaction with molecular hydrogen is a distinct possibility. Stepwise reduction of C02 with H2 may yield formic acid, formaldehyde, methanol and finally methane, together with CO or Fischer-Tropsch-type derivatives as shown on Scheme 3.42. In aqueous organometallic catalysis the most common product of such a reduction is formic acid. Formation of carbon monoxide, formaldehyde, and methane has already been reported, however, methanol and Fischer-Tropsch type products were not observed. 

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