3:4: 5-Triiodobenzoates

Triiodobenzoates. The derivatives enumerated above are unsatisfactory for alcohol - ethers, e.g., the mono-ethers of ethyleneglycol ( cellosolves ) and the mono-ethers of diethyleneglycol ( car-bitols ) (see Table 111,27). Crystalline derivatives of alcohol - ethers are readily obtained with 3 4 5-triiodobenzoyl chloride (for preparation, see Section VII,21), for example ... 

Triiodobenzoic acid [2338-20-7] M 499.8, m 289-290°. Crystd from aqueous EtOH. 

This reagent is used here for the diazotisation of 4-amino-3,5-diiodobenzoic acid in the preparation of 3,4,5-triiodobenzoic acid (cognate preparation in Expt 6.70). It is also used for the bis-diazotisation of m-phenylenediamine (the... 

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%). 

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