Phenols with sodium iodate

Pyrogullol U OXldlMtl by Ihc reagent in aqueous buffer to purpurogallin," but the yield (39%) is lowif thbn In oxidation with sodium iodate. Tropolone does nut react end hence behevilJMliyihi e eerboxylic ncid then e phenol. 

Procedure of Kline and Acree. For the determination of the aldose present it is preferable to take an aliquot of the sugar solution, or a weighed amount of the solid substance, which will react with approximately 20 ml. of 0.1 A iodine. Titrate this solution with 0.1 A sodium hydroxide or hydrochloric acid until it is exactly neutral to phenolphthalein. Add the phenolphthalein at this point only when it is necessary to bring the solution to neutrality and use only one drop, as the alcohol introduces a potential source of error involving a loss of iodine. A water solution of this indicator or of phenol red or thymol blue might be used for this titration. Add 5 ml. of 0.1 A iodine from a buret then add drop by drop from a buret 7.5 ml. of 0.1 A sodium hydroxide. Repeat this process until 22 ml. of iodine and 35 ml. of alkali have been added. This operation takes about five to six minutes. Allow a two-minute interval for the completion of the oxidation. Acidify with 0.1 A (or 0.2 A) hydrochloric acid to free the iodine from any sodium iodate present and titrate the liberated iodine with... 

Iodine water is added to an acetic acid sodium acetate buffered sample to reoxidise to iodate any iodine-containing substances produced by reduction of iodate by naturally occurring reducing substances present in the sample. Total iodate (i.e., iodate present in the original sample as iodate plus additional iodate produced by iodine water treatment) is then reacted with phenol solution at... 

Benzyl trimethyl ammonium dichloro iodate (3,1 moles) and sodium bicarbonate were stirred at ambient temp, with a solution of phenol in dichloromethane/methanol (2.5.1) for 7h. to give 2,4,6-triiodophenol. 

Leipert s method for determination of iodide is widely used, especially on solutions derived from the combustion of organic compounds containing iodine. This method depends upon the oxidation of iodide to iodate with bromine water, removal of the excess bromine by addition of some suitable reagent (phenol is widely used—see under Chiniofon Sodium, p. 315—but formic acid is most convenient), addition of iodide and titration of the liberated iodine with thiosulphate. The method has the great advantage that it gives a six-fold increase in the quantity of iodine to be titrated. A detailed procedure for its application will be found in Appendix IV, p. 800. 

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