Synthesis
General procedure for the synthesis of 4,5-dibromophthalic acid from 1,2-dibromo-4,5-xylene: 6.5 g (0.025 mol) of 1,2-dibromo-4,5-xylene was added to 200 ml of water, stirred to form a suspension and heated to boiling. 15.8 g (0.1 mol) of potassium permanganate powder was divided equally into three equal parts. One portion of potassium permanganate was added to the reaction mixture every two hours for a total of 6 hours. Upon completion of the reaction, the mixture was cooled to room temperature and sodium bisulfite was slowly added to reduce the remaining potassium permanganate until the magenta completely disappeared. Subsequently, the pH of the reaction mixture was adjusted to above 12 with potassium hydroxide. The reaction mixture was filtered through a Brewer's funnel to obtain a clarified colorless filtrate of potassium 4,5-dibromophthalate. The residue was washed twice with 1% KOH solution and the washes were combined into the filtrate. The filtrate was slowly acidified with concentrated hydrochloric acid (18 M) to a pH approximately equal to 2, at which time a large amount of white flocculent 4,5-dibromophthalic acid precipitate precipitated. It was filtered through a Brinell funnel and the filter cake was washed with a small amount of 1% hydrochloric acid solution and then dried in a silica gel dryer. 7.3 g of a sparkling white solid was finally obtained in 90% yield.
References
[1] Patent: CN105541850, 2016, A. Location in patent: Paragraph 0034; 0035; 0036
[2] Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999), 1980, p. 1834 - 1840
[3] Journal of the Chemical Society, 1952, p. 4615,4618
[4] J. Gen. Chem. USSR (Engl. Transl.), 1980, vol. 50, # 5, p. 907 - 915
[5] Zhurnal Obshchei Khimii, 1980, vol. 50, # 5, p. 1122 - 1131
