Thermal Transformation of Alkali Salts of Aromatic Carboxylic Acids. IV. Reaction of Potassium and Sodium Salts of Alkyl-and Phenylbenzoic Acids

Abstract

Abstract The cadmium halides-catalyzed thermal transformation of potassium and sodium salts of isomeric methyl- and phenylbenzoic acids has been investigated. Potassium o-toluate gave toluene, 3-methylphthalic, and 4-methylisophthalic acids, whereas sodium o-toluate gave toluene, 3-, and 4-methylphthalic acids, as the main products. In the reaction of potassium m- and p-toluates, both of them gave toluene, 5-methylisophthalic, and 4-methylphthalic acids, whereas the sodium salt of these acids gave toluene and 4-methylphthalic acid, as the main products. Potassium and sodium isomeric dimethylbenzoates gave xylenes and dimethylphthalic acids, e. g., 3, 4- and 4, 5-dimethylphthalic acids from 2, 3- or 3, 4-dimethylbenzoates, 3, 5-dimethylphthalic acid from 2, 4-dimethylbenzoate, and 3, 6-dimethylphthalic acid from 2, 5-dimethylbenzoate. In the case of o-phenylbenzoate, potassium salt gave biphenyl, m- and p-phenylbenzoic, and biphenyl-p-p′-dicarboxylic acids, but sodium salt gave biphenyl, m- and p-phenylbenzoic, and 4-phenyl-phthalic acids. Sodium p-phenylbenzoate gave biphenyl and 4-phenylphthalic acid, but potassium p-phenylbenzoate was stable under the conditions used. These results may be interpreted by the ortho-, meta-, and para-directed disproportionation for the potassium salts and ortho-di-rected one for the sodium salts. These dibasic acid salts produced were decarboxylated to mono-carboxylates, which then underwent further disproportionation.