Silver nitrate alcoholic

I he methyl iodide is transferred quantitatively (by means of a stream of a carrier gas such as carbon dioxide) to an absorption vessel where it either reacts with alcoholic silver nitrate solution and is finally estimated gravimetrically as Agl, or it is absorbed in an acetic acid solution containing bromine. In the latter case, iodine monobromide is first formed, further oxidation yielding iodic acid, which on subsequent treatment with acid KI solution liberates iodine which is finally estimated with thiosulphate (c/. p. 501). The advantage of this latter method is that six times the original quantity of iodine is finally liberated. 

Reaction with alcoholic silver nitrate. To carry out the test, treat 2 ml. of a 2 per cent, solution of silver nitrate in alcohol with 1 or 2 drops (or 0 05 g.) of the compound. If no appreciable precipitate appears at the laboratory temperature, heat on a boiling water bath for several minutes. Some organic acids give insoluble silver salts, hence it is advisable to add 1 drop of dilute (5 per cent.) nitric acid at the conclusion of the test most silver salts of organic acids are soluble in nitric acid. 

The alcoholic silver nitrate solution consists of a saturated solution of silver nitrate in absolute alcohol (about 1-2 per cent.). 

As esters the alkyl halides are hydrolysed by alkalis to alcohols and salts of halogen acids. They are converted by nascent hydrogen into hydrocarbons, by ammonia into amines, by alkoxides into ethers, by alkali hydrogen sulphides into mercaptans, by potassium cyanide into nitriles, and by sodium acetate into acetic esters. (Formulate these reactions.) The alkyl halides are practically insoluble in water but are, on the other hand, miscible with organic solvents. As a consequence of the great affinity of iodine for silver, the alkyl iodides are almost instantaneously decomposed by aqueous-alcoholic silver nitrate solution, and so yield silver iodide and alcohol. The important method of Ziesel for the quantitative determination of alkyl groups combined in the form of ethers, depends on this property (cf. p. 80). 

G and H both give an immediate precipitate upon reaction with alcoholic silver nitrate. This means that the bromine is probably attached to a tertiary carbon. 

Mercapto groups in poly(caprolactam) fibers having disulfide and alkalene sulfide cross-links have been determined by swelling the sample with methanol and titrating the suspended strips with an alcoholic silver nitrate solution [1,33]. 

To a flask containing 34.5 gm (0.53 mole) of sodium azide in 70 ml of water and 25 ml of methanol is added 68.5 gm (0.50 mole) of n-butyl bromide while stirring at room temperature. The resulting mixture is heated and stirred on a steam bath for 24 hr. The bottom layer of n-butyl bromide disappears after this time and a top layer of crude n-butyl azide forms. The crude azide is separated and then treated overnight with alcoholic silver nitrate to remove traces of butyl chloride. The mixture is then filtered, washed with water, and distilled behind a safety barricade to yield 40.0 gm (90 %) of n-butyl azide, b.p. 106.5°C (760 mm), n 9 5 1.4152, d29-5 0.8649. (NOTE n-Butyl azide and methanol form an azeotrope (b.p. 60°C) from which the azide is liberated by the addition of a saturated solution of calcium chloride.)... 

Below find mass spectra for compounds C-F. Compound C has an M + 1 peak that is 2.5% of M (where M = 100%). Compound F can easily be converted to compounds D and E. Compounds C-E each give precipitates when treated with alcoholic silver nitrate. The precipitate from D is white, the other two are yellow. Deduce the structures of C-F. 

B) Alcoholic silver nitrate method in which the following reaction takes place ... 

Halogen carriers, 533 Halogen compounds, reaction with alcoholic silver nitrate, 1059 reaction with sodium iodide in acetone, 1059, 1060 ... 

The resulting methyl (or ethyl) iodide is converted into silver iodide by the action of alcoholic silver nitrate, and the number of methoxyl (or ethoxyl) groups calculated from the weight of silver iodide formed. 

The hydriodic acid used is purified as described on p. 506, selecting for the determination the fraction of constant B.P. 127° and D. T68. The alcoholic silver nitrate, which is prepared by dissolving 4 gms. of silver nitrate in 10 c.cs. of water and adding 90 c.cs. of absolute alcohol, is preserved in a well-stoppered bottle in the dark, and should be filtered and acidified with one drop of nitric acid immediately before use. 

A reliable modification of the process for the estimation of methoxyl is that of the British Pharmacopoeia, 1932. The apparatus is shown in Fig. 80. A Pyrex flask (A) of about 100 c.cs. capacity, having a bulb (B) of about 70 c.cs. capacity blown on the side tube, contains the mixture of substance (about 0-2 gm.) and hydriodic acid (10 c.cs.). The side tube is connected through a smaller bulbed tube (0) to a set of bulbs (D, see Fig. 65), immersed in a water bath at 60° (95° for ethoxyl), containing red phosphorus suspended in a 2% aqueous solution of cadmium sulphate. To this is attached two absorption flasks (E), each containing about 20 c.cs. of the above alcoholic silver nitrate. To the flask (A) is... 

Cumming s Modification.—(J. S. 0.1., 41, 20.)—A convenient apparatus for the estimation of methoxyl groups by the Zeisel method consists of a long-necked round-bottomed flask attached by a ground-glass joint to a bulbed U-tube. The methyl iodide generated by the interaction of hydriodic acid and the methoxyl group is absorbed in alcoholic silver nitrate. Pyridine may also be used as absorbent. (J. C. S., 117, 193.) For purification of hydriodic acid, see p. 506. 

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