2.6- Diiodobenzoic acid

Amino-3 5-diiodobenzoic acid. In a 2 litre beaker, provided with a mechanical stirrer, dissolve 10 g. of pure p-aminobenzoic acid, m.p. 192° (Section IX,5) in 450 ml. of warm (75°) 12 -5 per cent, hydrochloric acid. Add a solution of 48 g. of iodine monochloride (1) in 40 ml. of 25 per cent, hydrochloric acid and stir the mixture for one minute during this time a yellow precipitate commences to appear. Dilute the reaction mixtiue with 1 litre of water whereupon a copious precipitate is deposited. Raise the temperature of the well-stirred mixture gradually and maintain it at 90° for 15 minutes. Allow to cool to room tempera-tiue, filter, wash thoroughly with water and dry in the air the yield of crude acid is 24 g. Purify the product by dissolving it in dilute sodium hydroxide solution and precipitate with dilute hydrochloric acid the yield of air-dried 4-amino-3 5-diiodobenzoic acid, m.p. >350°, is 23 g. 

The checkers found that 4-hydroxy-3,5-diiodobenzoic acid may be made from 4-hydroxybcnzoic acid using the above directions with the exception that the product is not recrystallized from acetone, in which it is only slightly soluble. The yield of 4-hydroxy-3,5-diiodobenzoic acid melting at 278-279° with decomposition is 59 g. (84 per cent of the theoretical amount). 

Amino-3,5-diiodobenzoic acid [2122-61-4] M 388.9, m >350 , pKesi(1)0.4, pKesi(2)-1.6. Purified by soln in dilute NaOH and pptn with dilute HCl. Air dried. 

C42H70O3S C7H4I202 6 H20 Cyclomaltoheptaose - 2,5-diiodobenzoic acid, hexahydrate (HPAMIB)333... 

Herbicides. The use of herbicides (qv) based on iodine compounds has its main market in Western Europe. In Canada and the United States these compounds are used only to a small extent. The only significant iodine-containing herbicide is ioxynil [1689-85 4] (4,-hydroxy-3,5,-diiodobenzoic acid). This compound, often used in combination with other herbicides, is formulated for controlling many annual broad-leaved weeds, especially black-bindweed, knotgrass, mayweeds, and com marigold post-emergence in wheat, barley, oats, rye, and triticale (142). Annual consumption of iodine in relation to ioxynils is considered to be about 300—500 t (66). 

Hydroxy-1 -cyclo-hexanecarbonitrile 2-Hydroxy-3,5-diiodobenzoic acid 2 -Hydroxy-4, 6 -di-methylaceto-phenone... 

I-)-Cl) with p-aminobenzoic acid both of the positions ortho to the amino group are substituted to give 4-amino-3,5-diiodobenzoic acid (cognate preparation in Expt 6.60). 

Triiodobenzoic acid. Dissolve 6.8g (0.0175 mol) of 4-amino-3,5-diiodobenzoic acid (Expt 6.60) in 30 ml of cold concentrated sulphuric acid, add a large excess (3.0 g, 0.0435 mol) of powdered sodium nitrite and allow the mixture to stand at 0°C for 2 hours. Treat the cold diazonium solution with a solution of 17.0g (0.12 mol) of potassium iodide in 40 ml of water a dark red precipitate separates. Warm the mixture on a water bath until evolution of nitrogen ceases, and remove any residual iodine with a little sodium metabisulphite. Filter the yellow precipitate of crude 3,4,5-trii-odobenzoic acid, and recrystallise from dilute ethanol. The yield of pure acid, m.p. 289-290 °C, is 6.8 g (78%). 

C7H4CtF02 2-chloro-6-fluorobenzoic acid 434-75-3 25 00 1.4016 2 9820 C7H4I203 2-hydroxy-3,5-diiodobenzoic acid 133-91-5 25.00 2.4343 2... 

C7H5CIF3N 5-amino-2-chiorobenzotrifluoride 320-51-4 25.00 1.4070 2 10038 C7H5I2N02 2-amino-3.5-diiodobenzoic acid 609-86-9 25.00 2.3815 2... 

C7H4I203 4-hydroxy-3,5-diiodobenzoic acid 618-76-8 533.15 47.078 2 10020 C7H5F4N 4-fluoro-3-(trifluoromethyl)aniline 2357-47-3 480.60 42.023 1,2... 

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