| 摘要 |
541,782. Brominated aromatic carboxylic acids. FACTOR & CO., M. June 5, 1940, No. 9849. Convention date, Sept, 22, 1939. [Class 2 (iii)) Aromatic carboxylic acids are brominated by a process which comprises gradually acidifying a mixture of the sodium or potassium bromide and hypochlorite and the sodium or potassium salt of the aromatic carboxylic acid while heating the mixture to about 70‹C. and continuing the heating of the mixture after it has been acidified to between 90‹-100‹C. until the re-action is complete, and separating the brominated acid from the re-action mixture. The separation may be effected by allowing the bromo-acid to crystallize out as the alkali salt followed by filtration, or an excess of hydrochloric acid may be added and the free bromo-acid crystallized. Alternatively the bromo-acid may be extracted from the reaction mixture by an organic solvent such as isopropyl alcohol, or dioxane. In an example phthalic anhydride is dissolved in caustic soda, sodium bromide and sodium hydro chlorite are added and the mixture is heated to 65‹-70‹C. during the gradual addition of hydochloric acid, after which the temperature is raised to 100‹C. The re-action mixture is acidified and extracted with dioxane. |
