Methiodides

Quinaldine Methiodide. Boil a mixture of 3 ml. of quinaldine, 2 ml. of methanol and 3 ml. of methyl iodide gently under reflux for hours, during which the methiodide will start to cry stallise. Cool the mixture thoroughly in ice-water, filter off the methiodide and recrystallise it from ethanol pale yellow crystals, m.p. 194". 

Dissolve a small quantity of the methiodide in cold water and add it with shaking to an excess of cold saturated aqueous sodium picrate solution. A yellow dovible salt of quinaldine niethoi icrate ami sodium picrafe. 

Members of Classes (i), (ii) and (iv) usually react readily with methyl iodide to give methiodides, i.e., quaternary ammonium iodides. 

Methiodide formation. Place 2 drops of dry pyridine in a dry test-tube, add 4-5 drops of methanol, and 2 -3 drops of methyl iodide. 

The mixture becomes hot, and on cooling the colourless crystals of the methiodide separate. 

B) Methiodi s. Members of Classes (i), (ii) and (iv) combine wdth methyl iodide (some very vigorously) to form quaternary methiodides. It is best to add the amine to an excess of methyl iodide dissolved in about twice its volume of methanol, allow any spontaneous reaction to subside, and then boil under reflux for 30 minutes (extend to 1 hour for Class (iv) except pyridine and quinoline). The methiodide may crystallise when the reaction-mixture cools if not, evaporate the latter to small bulk or to dryness, and recrystallise, (M.ps., pp. 553-554 )... 

Some methiodides may separate inftially as sticky syrups in this case, redissolve a portion in ethanol and add to an ethanolic solution of prcric acid, when the yellow methopicrate is usually precipitated, and when filtered off and recrystallised, has often a sharp m.p. (M.ps., pp. 553-554.)... 

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.)... 

Pyridine methiodide and ethiodide. Place 2 drops of dry pyridine in a test-tube, add 2 drops of methyl iodide and mix. A vigorous reaction occurs and on cooling, a colourless crystalline mass of pyridine methiodide, CjHjN.Mel, is formed cf. p. 377) when recrystallised from methylated spirit, the methiodide has m.p. 117. ... 

Tertiary Amines. Picrates (p. 378), Methiodides (p. 377), />-Nitroso-deriva-tives (p. 378). 

Methiodides. Methyl iodide reacts with tertiary amines to form the crystalline quaternary ammonium iodide (methiodide) ... 

Alternatively, dissolve 0-5 g. of the tertiary amine and 0-5 ml. of methyl iodide in 5 ml. of dry ether or benzene, and allow the mixture to stand for several hours. The methiodide precipitates, usually in a fairly pure state. Filter, wash with a little of the solvent, and recrystallise as above. 

A solution of 45 g of triphenyl phosphite methiodide in 100 ml of dry di-methylformamide was heated at 100°C and 0.08 mol of the acetylenic alcohol (commercially available) was added in 2 min. After stirring for 30 min at 100°C the mixture was cooled. The flask was equipped for vacuum distillation. On the flask were placed a 25-cm Vigreux column and two stoppers and the column was connected with a condenser and a receiver. The DMF and the iodoallene distilled between... 

As masked dicarbonyl compounds, enaminoketones (158) or vinylamidinium salts (159 160) can be employed (Scheme 84) (79S385). Similarly, 3-phenacylpyridinium methiodides... 

The methiodide of 2,5-dihydrothiophene (239) is transformed in high yield to Z)-l-(methylthio)buta-l,3-diene (240) on treatment with alkali (81AJC1017). The thermal cheletropic extrusion of sulfur dioxide from both cis and trans isomers of 2,5-dihy-drothiophene 1,1-dioxides is highly stereospecific. For example, c/5-2,5-dimethyl-2,5-dihydrothiophene 1,1-dioxide (241) yields ( , )-hexa-2,4-diene (242) and sulfur dioxide (75JA3666, 75JA3673). 

Benzo[0 furan, 7-dimethylamino-2,3-dihydro-3-hydroxy-2-methyl-, methiodide H NMR, 4, 548 <71JOC1805>... 

IH-l-Benzazepinium methiodide, tetrahydro-demethylation, 7, 511 lH-l-Benzazepin-2-one, 8-chloro-... 

Pyridine, 4-methoxy-3-styryl-photoelectron spectroscopy, 2, 137 Pyridine, 2-methyI-alkylation, 2, 176 amination, 2, 233, 236 carboxylation, 2, 53 chlorination, 2, 201, 331 Claisen condensation, 2, 51 methiodide... 

Pyridinium methiodide, 3-cyano-hydrogen-deuterium exchange, 2, 287 Pyridinium methiodide, 3-methyl-hydrogen-deuterium exchange, 2, 287 Pyridinium methosulfate, l-methoxy-3-methyl-reactions... 

Thiophene, 3,5-diethyl-2,4-diphenyl-synthesis, 4, 900 Thiophene, dihydroconformation, 4, 34 cycloaddition reactions, 4, 850 H NM 4, 10 methiodide, 4, 86 molecular structure, 4, 7 1-oxide... 

Propidium iodide (3,8-diamino-5-(3-diethylaminopropyl)-6-phenylphenantridinium iodide methiodide) [25535-16-4] M 668.4, m 210-230 (dec), pKeskd 4 (aniline NH2), pKesi(2) (EtN2). Recrystd as red crystals from H2O containing a little KI. It fluoresces strongly with nucleic acids. [Eatkins J Chem Soc 3059 7952.] TOXIC. 

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