Aryl Alkali-Metal Compounds (Organic Chemistry - Paul Karrer 1947)
Aryl compounds of the alkali-metals are formed with unexpected readiness by the action of the alkali metals on chloro-substituted aromatic compounds in the presence of an indifferent solvent, at a temperature not greater than about 40c. The aryl alkali-metal compounds produced can be used for further reactions without isolating them, or they can be produced in the presence of suitable reagents which combine with them as they are formed. They react with carbon dioxide with the formation of carboxylic acids; with benzonitrile they give ketones, e.g., benzophenone:
C6H5Na + NCC6H5 > C6H5C(=NNa)C6H5 >H2O> C6H5COC6H5
With sulphur dioxide they give sulphinic acids and with acetic anhydride they form mixed aromatic-aliphatic ketones. These compounds are therefore important starting substances for synthesis, resembling in this respect the alkyl magnesium salts.
Organic alkali-metal compounds of mixed aromatic-aliphatic hydrocarbons are also known. Sodium benzyl, C6H5CH2Na, and sodium triphenylmethyl, (C6H5)3CNa, are specially interesting on account of their red colour, and the fact that the sodium is linked ionically with the hydrocarbon radical.
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Lithium Alkyls may also be used in the synthesis of ketones. With dry carbon dioxide they react according to the scheme:
2RLi + CO2 > RCOOLi + RLi > RCR >H20> RCOR + 2LiOH
/ \
OLi OLi
giving di-lithium salts of the ketone hydrates, which break down on addition of water into ketones and lithium hydroxide (H. Gilman).
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