Iodine acetate purification

Procedures. Chromatographic Purification of Ozonization Products. Ozonization products from ethyl 10-undecenoate and 1-octene were chromatographed on silica gel columns (Baker) and eluted with 15 or 25% ether in petroleum ether (b.p., 30°-60°). Fractions were examined by thin-layer chromatography (TLC) on silica gel G Chroma-gram sheet eluted with 40% ether in petroleum ether. For development of ozonide and peroxide spots, 3% KI in 1% aqueous acetic acid spray was better than iodine. The spots (of iodine) faded, but a permanent record was made by Xerox copying. Color of die spots varied from light brown (ozonide) to purple-brown (hydroperoxide), and the rate of development of this color was related to structure (diperoxide > hydroperoxide > ozonide). 2,4-Dinitrophenylhydrazine spray revealed aldehyde spots and also reacted with ozonides and hydroperoxides. Fractions were evaporated at room temperature or below in a rotary evaporator. 

To a freshly prepared catalyst (1 g, 0.2 mmol of iodine) under stilling, a mixture of benzaldehyde la (2 mmol) and ethane-1,2-dithiol (2.2 mmol) was added and stirring continued for 10 min or till the reaction was complete. For TLC monitoring, a small amount of the solid reaction mixture was taken out with a spatula and washed with a little amount of ethyl acetate to get a solution. On completion the reaction mixture was loaded on a short column of silica gel (60 to 120 mesh) and eluted with ethyl acetate. The organic layer was washed with a dilute solution of sodium thiosulfate followed by water and dried over anhydrous sodium sulfate. Evaporation of the solvent under reduced pressure and purification of the residue by column chromatography yielded the pure product. 

For purification, the crystalline hexaatomic sulfur is dissolved in benzene (approx. 100 mg./l.) toluene is not suitable (see Properties). The benzene solution is extracted with a series of reagents, three or four extractions being made with each reagent except where otherwise indicated. (For 200 ml. of benzene solution, 50-ml. portions of reagent are used). The reagents are employed in the following order (1) water, (2) 10% aqueous potassium triiodide, until the benzene phase remains colored from iodine, (3) 10% aqueous potassium iodide, (4) water, (5) 5% aqueous lead acetate, twice, (6) water, (7) 5 % aqueous potassium hydroxide, once, (8) water. The purified solution is dried over magnesium sulfate and should be used immediately. The approximate concentration of Sg can be determined spectro-photometrically at 300 mju (e = 181 l./g.-atom) after suit-... 

The reagent has been prepared in 74% yield by dropwise addition of u. solulion of iodine monochloride in carbon tetrachloride to an ice-cold aqueous solution of 5,5-dimethylhydantoin and an equivalent amount of sodium hydroxide. The precipitated product was collected, washed with ice water and with ethyl acetate, dried in vacuum at 60°, and used without further purification. It effects nuclear iodinatiun of only... 

To a mixture of cyclic ether (6.90 mmol) and acyl chloride (0.69 mmol), a catalytic amount of iodine (10 mol%) was added. The reaction mixture was stirred at room temperature under a nitrogen atmosphere for an appropriate time. After completion of the reaction, as indicated by TLC, the reaction mixture was quenched with saturated aqueous sodium bicarbonate solution (15 mL) and extracted with ethyl acetate (2x15 mL). Evaporation of the solvent followed by purification on silica gel (Merck, 100-200 mesh, ethyl acetate-hexane, (0.5 9.5) afforded the pure ester derivatives. 

Iodine, m.p. 113.6°, sublimes readily, a property that can be used for its purification. To remove chlorine or bromine present as impurity, sublimation is effected in presence of potassium iodide. Iodine is only slightly soluble in water (0.28 g/1 at 20°), but readily so in mineral acids or aqueous potassium iodide (15.9 g/1 in 0.12n-KI and 420 g/1 in 1.9n-KI). At room temperature iodine dissolves readily in ether, methanol, ethanol, CS2, or benzene, and moderately in acetic acid, CHC13, CC14, and light petroleum. Iodine can be dried in a desiccator over calcium chloride, concentrated sulfuric acid, or phosphorus pent-oxide. It is not hygroscopic. For the preparation of very pure iodine see reference1 ... 

Tetrahydropalmatine yields a hydrochloride which is moderately soluble in boiling water and only sparingly soluble in cold water. This property, together with the fact that the hydrochloride is readily extractable from hydrochloric acid solutions of plant extracts by means of chloroform, renders its isolation and purification a simple procedure. The hydrochloride of the dZ-form is appreciably less soluble than that of the d- or Z-forms and separates in stout prisms even from hot aqueous solutions. The alkaloid is readily oxidized by air and slowly becomes yellow owing to the formation of palmatine. This oxidation can be readily completed by means of alcoholic iodine solutions when palmatine iodide is formed, or it may be brought about by heating in dilute acetic acid with mercuric acetate (224). 

The process, first disclosed in 1968, was commercialized in 1973. Yields in this process were very high (99%) and ease of operation was excellent. The major difficulty encountered was with catalyst precipitation during product removal. To minimize the problematic catalyst precipitation and to stabilize the catalyst, 10-15% water was included in the reaction mixture and the catalyst -product separation was conducted as an adiabatic flash. The inclusion of large amounts of water and the restriction to an adiabatic flash meant that the conversion was limited by product removal, not the reaction rate, and that there were large recycle streams of acetic acid and water. Additional minor difficulties were the cogeneration of traces of acetaldehyde which ultimately lead to propionic acid and iodine containing impurities. While the propionic acid was removable by distillation (with a dedicated unit of operation), the iodine has proven more problematic. It was important to remove essentially all the iodine (to < 40 ppb) during purification since iodine is a poison for the Pd/Au catalyst used in vinyl acetate production. 

They also demonstrated that inexpensive molecular iodine can be used as a cheap, nontoxic, general, and fast catalyst for one-pot tandem acetalation-esteri-fication reactions of glycosides in good to excellent yields without the need of purification after every reaction step. Further, the addition of catalytic DMAP can be used to accelerate the esterification step and thus shorten the reaction times. The method is mild and compatible with different thioglycosides and 0-glycosides, applicable to the formation of 4,6-0-benzylidene and 4,6-0-p-methoxybenzylidene acetals in tandem reaction with either 2,3-0-di-acetate or 2,3-0-di-benzoate esters and also amenable to commonly used amino-protecting groups (e.g., phthalimides and 2,2,2-trichloroethoxycarbonyl chloride). 

The stability of hypertensin is maximum between pH 1.5 and 8.5, but as the purification progresses, the stability decreases. Outside of this pH range, the destruction of hypertensive activity increases considerably, especially in alkaline media. Hydrogen peroxide, bromine water, iodine, nitrous acid, hydroxylamine, lead acetate, destroy this activity. 

One method which gave a purification of iodine-131 from a 16-day-old solu-tion of 10 fissions had the following steps (224). Iodide, iodate, or periodate carrier and sodium chlorate were added to the sample which contained only inorganic substances (but no gold) and no reducing agents. The solution was made 6-10 in hydrochloric acid in order to produce iodine monochloride (yellow-green solution). The monochloride was extracted into butyl acetate and then back-extracted into water as iodide by means of sulfurous acid. Iodide was oxidized to elemental iodine with iron(III) chloride in dilute sulfuric acid and the iodine extracted into toluene. The element was back-extracted into water as iodide by sulfurous acid and palladium(II) iodide was precipitated. 

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