| 摘要 |
Tri- and multi-basic benzene carboxylic acids or derivatives thereof are obtained from methyl-substituted benzenes such as xylenes, crude xylenes, mesitylene, pseudocumene and durene and their derivatives such as nitroxylenes, by converting the methyl-benzenes, by side-chain chlorination and chroromethylation, into chloromethylated benzenes of formula C6H3-0[(CH2)Cl]3-6, which are oxidized with nitric acid to substantial freedom from chlorine and the resultant acids are separated from the reaction mixture. The chloromethylation is carried out using chloromethyl ether of hydrogen chloride and formaldehyde and the side-chain chrorination is carried out in the molten state with chlorine at 120 DEG to 130 DEG C. The chlorination and chloromethylation reactions may be effected in either order. Oxygen or an oxygen-containing gas, e.g. air, is preferably passed through the oxidation mixture. The oxidation products are separated from the reaction mixture and freed from chlorine-containing compounds by washing with a solvent, preferably the initial methyl-benzene, which may then be used as starting material. In an example, crude xylene is reacted with hydrochloric acid and formaldehyde to give a bis-chloromethyl-xylene which is chlorinated to give a tetrachloromethyl - benzene. Other methyl-benzenes are converted into chloromethyl-benzenes similarly and oxidized, the results being shown in a table. Thus, xylene is converted into a tri-(1 : 2 : 4)- or tetra-(1 : 2 : 4 : 5)-chloromethyl-benzene which on oxidation give trimellitic and pyromellitic acids, mesitylene gives penta-chloromethyl-benzene and benzene pentacarboxylic acid and durene gives hexa-chloromethyl-benzene and mellitic acid. Specification 771,086 is referred to. |
