Halogenated fatty acids and their salts

For %-halo aliphatic acids it is the rule that the ease of loss of carbon dioxide increases with the atomic weight of the halogen. For example, trichloroacetic acid can be distilled unchanged and decomposes only at temperatures above 200°, and then slowly triiodoacetic acid, however, is decarboxylated at its melting point, 150°. 

Trichloroacetic acid is stable in toluene, carbon disulfide, or 6N-sulfuric acid, i.e., in solvents having little or no proton-acceptor properties. The situation is different in basic solvents, e.g., in water in aqueous solution trichloroacetic acid decomposes to chloroform and carbon dioxide when warmed to 70°. Thus the undissociated acid is moderately stable, but the anion is not. Cor- 

Sodium trichloroacetate (40 g) and cyclohexene (105 g) are heated in 1,2-dimethoxyethane (70 ml) for 22 h under reflux, after which they afford dichloronorcarane in 65 % yield (23.1 g) calculated on the trichloroacetate. 

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