Triphenyl iodine

The next reaction in this sequence is an Appel reaction, which transforms an alcohol to an alkyl iodide. The simplified mechanism is depicted in the margin. The initial step of this reaction is the nucleophilic attack of triphenyl phosphine to iodine with formation of an iodine triphenyl phosphonium cation. The positive charge increases the oxophilicity of phosphorus, which is attacked in the next step by an alcohol. After elimination of hydrogen iodide, the resulting alkoxy triphenyl phosphonium cation is attacked by an iodide anion in an SN2-type reaction. Therefore, the reaction of chiral alcohols typically proceeds with inversion of configuration, although other behavior is also reported. The product of the Appel reaction is alkyl iodide 37 and triphenyl phosphine oxide is formed as byproduct. ... 

The aHphatic iodine derivatives are usually prepared by reaction of an alcohol with hydroiodic acid or phosphoms trHodide by reaction of iodine, an alcohol, and red phosphoms addition of iodine monochloride, monobromide, or iodine to an olefin replacement reaction by heating the chlorine or bromine compound with an alkaH iodide ia a suitable solvent and the reaction of triphenyl phosphite with methyl iodide and an alcohol. The aromatic iodine derivatives are prepared by reacting iodine and the aromatic system with oxidising agents such as nitric acid, filming sulfuric acid, or mercuric oxide. 

Imidazole, 1 -hydroxy-2,4,5-triphenyl-3-oxides reactions, S, 455 Imidazole, iodo-nitrodehalogenation, 5, 396-397 Imidazole, 1-iodo-reactions, S, 454 stability, S, 110 Imidazole, 2-iodo-synthesis, S, 401 Imidazole, N-iodo-, S, 393 reactions, 5, 454 Imidazole, 4-iodo-5-methyl-iodination, 5, 400 Imidazole, 2-isopropyl-4-nitro-N-nitration, 5, 351 Imidazole, 2-lithio-reactions, S, 106, 448 Imidazole, 2-mercapto-l-methyl-as antithyroid drug, 1, 171 mass spectra, 5, 358 Imidazole, 1-methoxymethyl-acylation, S, 402 Imidazole, 5-methoxy-l-methyl-reactions... 

The liberated iodine may be titrated using std thiosulfate soln, or, in trace analysis, detd by spectrophotometric methods. Other reducing agents commonly used in peroxide analysis are hydriodic acid, ferrous, titanous, stannous, and arsenious ions. Also (recently), triphenylphos-phine, which is oxidized to triphenyl phosphine oxide. The excess triphenyl phosphine may be detd gravimetric ally, tit rime trically, or spectro-photometrically... 

Gram Stain A staining procedure used in classifying bacteria. A bacterial smear on a slide is stained with a purple basic triphenyl methane dye, usually crystal violet, in the presence of iodine/potassium iodide. The cells are then rinsed with alcohol or other solvent, and then counter-stained, usually with safranin. The bacteria then appear purple or red according to their ability to keep the purple stain when rinsed with alcohol. This property is related to the composition of the bacterial cell wall. 

The compound 4(Ph3SbI)2OI2 is obtained by the addition of I2 in acetonitrile/water to a solution of triphenyl-antimony. The crystal structure contains a one-dimensional chain 53 and (Ph3SbI)20 molecules which are not coordinated to I2. In the ID chain, the distance between the iodine of the (Ph3SbI)20 molecule and the diiodine... 

Reactions of a number of l-phenylimidazole-2-carboxamides with chlorine in acetic acid, NCS, or hypochlorite failed to introduce chlorine into the 4- or 5-positions (80JHC409). Chlorination of a variety of 2,4-disubstituted imidazoles, however, was quite facile, Thus, 2,4-diesters [83JCS(P1)809] and 2-amino-4-aryl compounds [80IJC(B)526] were readily 5-chlorinated, and even when both the 4- and the 5-positions were blocked, as in 5-aminoimidazole-4-carboxamide, 2-chlorination with iodine monochloride was possible (89MI5). When all three carbons were substituted (e.g., in 2,4,5-triphenyl-, 2-chloro-4,5-diphenyl-, and 2-trichloromethyl-... 

Triphenyl-X -phosphorin interacts with iodine or other polarizable electron donors, as well as with such electron acceptors as tetrachloro-p-benzoquinone and tetracyanoethylene, to produce deeply colored solutions. Such coloration points to the formation of charge-transfer complexes (see p. 43). In some cases electron transfer occurs with the formation of 2.4.6-triphenyl-X -phosphorin cation radical and tetracyanoethylene anion radical. Weber is currently investigating the details of these reactions (see p. 43). 

These reactions are related to the reaction of aryl diazonium salts with iodide yielding iodoaryls, the mechanism of which seems to be a one-electron transfer (radical) reaction and not a nucleophilic displacement. Just as iodide is easily oxi- zed to iodine by the aryl diazonium cation, 2.4.6-triphenyl-X -phosphorin is oxidized to the radical cation 58. 

Minor industrial uses include the application of silver iodide as a smoke for the seeding of clouds to induce rainfall. Compounds used for obtaining some nonflammable plastics and cellulose are benzyltriphenyl-phosphoniumiodides and [2,-(acetyloxy)ethyl] triphenyl-phosphoniumiodides (see Flame RETARDANTS, HALOGENATED FLAME retardants) (142). The addition of iodine to an aromatic hydrocarbon such as -butylbenzene results in the formation of charge-transfer complexes that display outstanding effectiveness as lubricants for hard-to-lubricate metals (143), such as titanium or steels (see also LUBRICATION AND LUBRICANTS). Iodine is also used in the production of high purity metals such as titanium, silicon, hafnium, and zirconium (144). 

Biphenyldiyl 2-bromo-2 -biphenyl telluronium bromide (m.p. 264°, yield 79%) and the corresponding iodine compound (m.p. 265c, yield 63%) were similarly prepared2,3. Tetraphenyl tellurium transferred an anionic phenyl group to benzaldehydc and triphenyl boron yielding triphenyl telluronium salts4. 

Appropriate triphenyl telluronium halides dissolved in chloroform were treated with a slight excess of bromine or iodine. Addition of diethyl ether to the reaction mixture precipitated triphenyl telluronium trihalides4... 

In the presence of iodine promoters such as hydrogen iodide (Co I = 1 2), the additiun of triphenyl phosphine effects good conversions and selectivities... 

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