Sodium -iodide

Sodium iodide [7681-82-5] Nal, occurs as colorless crystals or as a white crystalline solid. It has a salty and slightly bitter taste. In moist air, it gradually absorbs as much as 5% water, which causes caking or even Hquefaction (dehquescence). The soHd slowly becomes brown when exposed to air because some iodide is oxidized to iodine. Water solutions are neutral or slightly alkaline and gradually become brown for the same reason. Aqueous solutions are stabilized with respect to oxidation by raisiag the pH to 8—9.5 (see Iodine and iodine compounds). 

Sodium iodide crystallizes ia the cubic system. Physical properties are given ia Table 1 (1). Sodium iodide is soluble ia methanol, ethanol, acetone, glycerol, and several other organic solvents. SolubiUty ia water is given ia Table 2. 

Below 65°C, sodium iodide is present ia aqueous solutions as hydrates containing varyiag amounts of water. When anhydrous sodium iodide is dissolved ia water, heat is Hberated because of hydrate formation, eg, AH = —174.4 kJ/mol (—41.7 kcal/mol), when the dihydrate is formed. At room temperature, sodium iodide crystallizes from water as the dihydrate [13517-06-1/, NaI-2H2 02H2O, ia the form of colorless prismatic crystals. 

Bulk production of United States Pharmacopeia (USP) and reagent grades is based on the reaction of sodium carbonate or hydroxide with an acidic iodide solution, typically hydriodic acid or a metal iodide. After removal of chemical impurities, the solution is filtered and concentrated. Evaporation gives the anhydrous Nal. Controlled cool-down produces either the dihydrate or the pentahydrate [81626-33-7]. 

Essentially no waste products are formed ia the USP process if hydriodic acid and either sodium hydroxide or sodium carbonate are used as reactants. Water results from use of the former a mole equivalent quantity of carbon dioxide is produced from the latter reagents. Higher quaUty grades may require some purification steps which may result ia wastes from the treatment. Disposal of these impurities must then be carried out. 

The market price of USP sodium iodide generally follows the price of cmde iodine multiplied by a factor of 1.8—2. Higher purity grades are only marginally related to the price of cmde iodine. 

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Iodine is rarely prepared in the laboratory the method used is the oxidation of an iodide by manganese(IV) oxide and sulphuric acid, for example with sodium iodide ... 

Thus, to name just a few examples, a nucleophilic aliphatic substitution such as the reaction of the bromide 3.5 with sodium iodide (Figure 3-21a) can lead to a range of stereochemical products, from a l l mbrture of 3.6 and 3.7 (racemization) to only 3.7 (inversion) depending on the groups a, b, and c that are bonded to the central carbon atom. The ring closure of the 1,3-butadiene, 3.8, to cyclobutene... 

Now cork the flask securely, and shake it vigorously for about 5 minutes the solution should now have only a faint brown colour due to unchanged iodine. Cool the mixture in ice-water, pour it into a separating-funnel, and extract it twice with water to remove sodium iodide and most of the ethanol. Then shake the residual ethereal solution with a dilute aqueoussolution of sodium thiosulphate the excess of iodine is thus removed and the... 

As(ONa), -I- CH,I — [CH,As(ONa)jI] CH,AsO(ONa), — CH,AsO(OH), unstable product losing sodium iodide to form disodium methylarsonate, which on acidification liberates methylarsonic acid. Note that this synthesis is limited to alkylarsonic acids, whereas the Bart synthesis (p. 312) is limited to aiy larsonic acids. 

Some less reactive tertiary amines can be mixed with an excess of methyl toluene-/)-sulphonate, m.p. 28 , and the mixture (without a solvent) heated to a much higher temperature. The mixture is allowed to cool, but before solidification occurs, it is thoroughly stirred with ether to extract unused sulphonate, and the insoluble quaternary metho-toluene-/)-sulphonate may then crystallise. If ciystallisation does not occur, dissolve this residue in ethanol and treat one portion with ethanolic picric acid (to precipitate the methopicrate) and another portion with cold concentrated ethanolic sodium iodide (to precipitate the methiodide). (M.ps. of the siilphon.ates, pp. 553 -554.)... 

The Iodine may be recovered from the aqueous filtrate, containing sodium iodide, in the following manner. Add 33 ml. of concentrated sulphuric acid and a solution of 65 g. of sodium dichromate in 65 ml. of water. Allow the iodine to settle, wash it three times by decantation, filter, and allow to dry on a clock glass. The weight of crude iodine is about 50 g. 

To determine the exact peroxide content of benzoyl peroxide (and of other organic peroxides) the following procedure may be employed. Place about 0 05 g. of the sample of peroxide in a glass-stoppered conical flask add 5-10 ml. of acetic anhydride (A.R. or other pure grade) and 1 g. of powdered sodium iodide. Swirl the mixture to dissolve the sodium iodide and allow the solution to stand for 5-20 minutes. Add 50-75 ml. of water, shake the mixture vigorously for about 30 seconds, and titrate the liberated iodine with standard sodium thiosulphate solution using starch as indicator. 

To determine the exact perbenzoic acid content of the solution, proceed as follows. Dissolve 1 -5 g. of sodium iodide in 50 ml. of water in a 250 ml. reagent bottle and add about 5 ml. of glacial acetic acid and 5 ml. of chloroform. Introduce a known weight or volume of the chloroform solution of perbenzoic acid and shake vigorously. Titrate the liberated iodine with standard O lA sodium thiosulphate solution in the usual manner. 

It consists in treating a solution of sodium iodide in pure acetone with the organic compound. The reaction is probably of the S 2 type involving a bimolecular attack of the iodide ion upon the carbon atom carrying the chlorine or bromine the order of reactivities of halides is primary > secondary > tertiary and Br > Cl. 

Prepare the reagent by dissolving 7 -5 g. of sodium iodide in 50 ml. of A.R. acetone. The colourless solution gradually acquires a yellow colour. Keep it in a dark bottle. When a red-brown colour develops, it should be discarded. 

Apply the test to compounds which contain chlorine or bromine. If the compound is a solid, dissolve 0 1 g. in the minimum volume of pure, dry acetone. To 1 ml. of the sodium iodide acetone reagent add 2 drops of the compound (if a hquid) or the acetone solution (if a sohd). Shake and allow to stand at room temperature for 3 minutes. Note whether a precipitate is formed and also whether the solution acquires a reddish-brown colour (liberation of iodine). If no change takes place at rocrm temperature, place the test-tube in a beaker of water at 50°. After 5 minutes, cool to room temperature, and observe whether a reaction has occurred. 

In the flask were succesively placed 0.10 mol of the sulfinate (note 2), 25 ml of dry, pure HMPT (note 3), 4 g of powdered sodium iodide, 40 g of zinc dust and some boiling stones. After swirling for a few seconds the flask was connected with the other parts of the distillation apparatus, the system was evacuated immediately by means of the water pump (note 4) and the flask was then heated cautiously (free flame). A vigorous reaction started suddenly and the cumulene and part of the HMPT passed over. When the distillation had stopped completely... 

A solution of 92 g of dry sodium iodide in 350 ml of 100% ethanol (note 1) was heated to about 70°C. Freshly distilled propargyl bromide (note 2) (0.50 mol) was added in 10 min. After heating for 20 min at 70-75°C the white suspension was cooled to room temperature and 500 ml of water were added, then the product was... 

C—C double bonds may be protected against electrophiles by epoxidation and subsequent removal of the oxygen atom by treatment with zinc and sodium iodide in acetic acid (J.A. Edwards, 1972 W. Kndll, 1975). Halogenation has often been used for protection, too. The C—C double bond is here also easily regenerated with zinc (see p. 138, D.H.R. Barton, 1976). 

Iodide ion (I ) Alkyl chlorides and bromides are converted to alkyl iodides by treatment with sodium iodide in acetone Nal is soluble in acetone but NaCI and NaBr are insoluble and crystallize from the reaction mixture making the reac tion irreversible... 

Identify the compound in each of the following pairs that reacts with sodium iodide in acetone at the faster rate... 

Arrange the isomers of molecular formula C4H9CI in order of decreasing rate of reaction with sodium iodide in acetone... 

Wnte an equation clearly showing the stereochemistry of the starting material and the prod uct for the reaction of (S) 1 bromo 2 methylbutane with sodium iodide in acetone What is the configuration R or S) of the product" ... 

In a classic expenment Edward Hughes (a colleague of Ingold s at University College Lon don) studied the rate of racemization of 2 lodooctane by sodium iodide in acetone and compared It with the rate of incorporation of radioactive iodine into 2 lodooctane... 

Sodium iodide [7681-82-5] Nal, mol wt 149.92, mp 662°C, 84.66% I, forms colorless cubic crystals, which are soluble in water, ethanol, methanol, and acetone. It is used in photography, for the production of organic chemicals, and as an expectorant in cough medicines. Nal is separated by addition of sodium hydroxide or sodium carbonate to an acidic iodide solution (see also Expectorants, antitussives, and related agents). 

Scintillation detectors are substances which fluoresce when stmck by x-radiation. Scintillation can, therefore, serve to convert x-ray photons into visible or ultraviolet light. Scintillation materials include thaUium-activatedcrystals of sodium iodide, NaI(Tl), potassium iodide, KI(T1), or cesium iodide, CsI(Tl) crystals of stilbene (a, P-diphenylethylene) [588-59-0] and anthracene [120-12-7] bismuth germanium oxide [12233-56-6] ... 

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