Натрия йодид

Химические свойства

White or almost white, crystalline powder or colourless crystals, hygroscopic.

Физические свойства

Physical Properties White crystalline deliquescent powder or granules; saline and slight bitter taste; absorbs moisture from air; slowly turns brown on exposure to air due to iodine evolved; density 3.67g/cm³; melts at 660°C; vaporizes at 1,304°C; vapor pressure 1 torr at 767°C and 5 torr at 857°C; very soluble in water, 178.7 g/100 mL at 20°C and 294 g/100 mL at 70°C; soluble in ethanol and acetone.

Использование

Sodium iodide is widely used for halide exchange (Finkelstein reaction), for example in the conversion of an alkyl chloride, allyl chloride and arylmethyl chloride into their respective iodides, which are precursors for pharmaceutical and fine chemical products. They are used to ehnance the efficiency of the formation of Wittig adducts from less reactive chlorides and bromides. Appropriate prepartions find use as a nutrient supplement. Sodium iodide is used as the precursor to the control agent in ab initio emulsion polymerization. Sodium iodide finds use in the determination of dissolved oxygen in the modified Winkler method, synthesis of the fluorescent dye coppersensor-1 (CS1) for imaging labile copper pools in biological samples, and the cleavage of esters, lactones, carbamates and ethers in combination with chlorotrimethylsilane.

Подготовка

Sodium iodide is prepared by adding hydriodic acid or an acidic iodide solution to a solution of sodium hydroxide or sodium carbonate, followed by evaporation and crystallization: NaOH + HI → NaI + H₂O
The solution is filtered to remove any impurities prior to its evaporation and crystallization.

Определение

sodium iodide: A white crystallinesolid, NaI, very soluble in water andsoluble in both ethanol and ethanoicacid. It is known in both the anhydrousform (cubic; r.d. 3.67; m.p.661°C; b.p. 1304°C) and as the dihydrate(monoclinic; r.d. 2.45). It is preparedby the reaction of hydrogeniodide with sodium carbonate orsodium hydroxide in solution. Likepotassium iodide, sodium iodide inaqueous solution dissolves iodine toform a brown solution containingthe I₃^- ion. It finds applications inphotography and is also used in medicineas an expectorant and in the administrationof radioactive iodine for studies of thyroid function and fortreatment of diseases of the thyroid.

Общее описание

Sodium iodide is an inorganic salt. Mixture of chlorotrimethylsilane/sodium iodide in acetonitrile is a useful reagent for the cleavage of esters, lactones, carbamates and ethers.

Профиль безопасности

Moderately toxic by ingestion, intravenous, and intraperitoneal routes. Human teratogenic effects by ingestion: developmental abnormalities of the endocrine system. Human reproductive effects by ingestion: effects on newborn, including postnatal measurements. A skin and eye irritant. Reacts violently with BrF3, HClO4, oxidants. When heated to decomposition it emits toxic fumes of Iand Na2O. See also IODIDES.

Методы очистки

Crystallise NaI from water/ethanol solution and dry it for 12hours under vacuum, at 70o. Alternatively, dissolve it in acetone, filter it and cool it to -20o; the resulting yellow crystals are filtered off and heated in a vacuum oven at 70o for 6hours to remove acetone. The NaI is then crystallised from very dilute NaOH, dried under vacuum, and stored in a vacuum desiccator [Verdin Trans Faraday Soc 57 484 1961].