Alkali iodides, replacement

Chlorine and bromine can be replaced by iodine by means of alkali iodide, and this is of importance in cases where direct treatment of alcohols with hydriodic acid gives a bad yield or none at all, e.g. in the preparation of ethylene iodohydrin ... 

The aliphatic iodine derivatives are usually prepared by reaction of an alcohol with hydroiodic acid or phosphorus triiodide by reaction of iodine, an alcohol, and red phosphorus addition of iodine monochloride, monobromide, or iodine to an olefin replacement reaction by heating the chlorine or bromine compound with an alkali iodide in 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 oxidizing agents such as nitric acid, fuming sulfuric acid, or mercuric oxide. 

Introduction. In the preceding experiment it was shown that an aqueous solution of a diazonium salt treated with a solution of an alkali iodide gives iodobenzene. The replacement of the diazo group, N2X, by chlorine or bromine atoms involves the catalytic action of copper salts. Thus, benzenediazonium chloride warmed with a solution of cuprous chloride and hydrochloric acid gives chlorobenzene with cuprous bromide, bromobenzene is formed. The use of the cuprous salt is known as the Sandmeyer method. Instead of cuprous salts, finely divided copper may be used according to Gatterman s method. 

Replacement 1. Chlorine and bromine may be replaced by iodine in many compounds by heating the derivative with an alkali iodide ... 

When treated with aleoholie alkalis the y-methoxyl group in skimmianine is replaced by the alkyloxy group of the alcohol used. The ethoxy-analogue, C1JH15O4N, has m.p. 138°, yields a picrate, m.p. 194°, is re-converted to skimmianine by boiling with methyl alcohol, with methyl iodide yields woskimmianine, and is oxidised to the ethoxy-analogues of skimmianal, m.p. 212°, and skimmianic acid, m.p. 225° (I EtO in 4). 

Metal halides can in some cases, be used to replace other atoms or groups besides fluorine with halogen Polyfluoroacyl fluorides and chlorides can be converted to fluoroalkyl iodides by simply heating the reactant in the presence of an alkali metal iodide [[Pg.382]

Analogs of the dichloro complex are prepared by a variety of methods, many of which are specific for single compounds. The dibromo complexes can be prepared using nitrosyl bromide or from A-methyl-iV-nitrosotoluene-4-sulfonamide and rhodium tribromide. Replacement of the tribromide by the trichloride and an alkali metal iodide gives diiodo complexes (equations 50 and 51). 

Thus, making use of (the rather mild oxidant) iodine pentafluoride, iodide can be replaced by fluoride even though soft class B metals strongly prefer iodo to fluoro ligands, hence there would be no reaction of the above iodo(-chloro)metallate with either HF or alkali fluorides. 

The nitroaminoarylarsinic acids are yellow or colourless solids, often soluble in hot water and alkali, but sparingly soluble in cold dilute mineral adds. The amino-group may be acetylated, diazotised, and coupled in the usual way. Mild reduction yields di- and triaminoaryl derivatives. MTien the sodium salts of 5-nitro-2-amino- and 3-nitro-4-aminophenylarsinic adds are boiled with potassium iodide and dilute sulphuric add, the arsinic add grouping is replaced by iodine, whilst bromine in alkali converts 3 5-dinitro-4-aminophenylarsinie add to... 

The hydroxyl-hydrogen atoms of alizarin may be replaced by alcohol and acid radicals. The alkyl derivatives are easily obtained by heating alizarin with the requisite alkyl iodide in presence of caustic alkali. Mono- and di-derivatives may he obtained in this manner [5, 6]. 

The new aniline dye companies in Europe displayed their wares at the 1862 London International Exhibition, where Hofmann, as juror, acquired a number of samples. They included a blue (7) discovered, almost by chance, by two French chemists working near London in 1861. It had first appeared when excess aniline was erroneously added to the aniline red reaction mixture. E. C. Nicholson in 1862 treated the aniline blue with sulfuric acid to yield a more valuable product, the soluble alkali blue, later better known as Cl [Colour Index] Pigment Blue 61. In May 1863, Hofmann found that the aniline blue was a substitution product of aniline red in which three phenyl groups had replaced three hydrogens (Scheme 2). This immediately suggested that other substituted derivatives might be made and perhaps even provide new aniline dyes. Alkylation with ethyl iodide showed that this was indeed correct. Hofmann achieved stepwise replacement of three hydrogens to afford colorants that were, successively, reddish violet, violet blue and then violet, what were soon known as the Hofmann s violets (8). Hofmann next turned to the aniline red process, and found that the colorant was formed not from aniline alone... 

I.r. studies have been made at 10 and 310 K of caesium cyanate and of NCO isolated in caesium iodide by employing the alkali-metal halide pressed disc technique. On replacing CsCNO by KCNO, heating for several hours at 673 K was necessary to encourage diffusion away of ions and prevent absorptions due to KCNO appearing with aging. ... 

However, a second pathway (Figure 26.7) in which Lil replaces HI is found to be extremely important for efficiency of the process the final product is formed by the reaction of acetyl iodide and lithium acetate. Other alkali metal iodides do not function as well as Lil, e.g. replacing Lil by Nal slows the reaction by a factor of 2.5. 

Recently, however, Kornblum et al.651 showed that alkali nitrites, in particular sodium nitrite, can replace silver nitrite in the preparation of nitro compounds if dimethylformamide is used as solvent. The method has the additional advantage that not merely primary but also secondary alkyl iodides and bromides react readily in this solvent. Yields are around 60% in both cases. It usually suffices to stir the halide with an excess of sodium nitrite in dimethylformamide for some hours at room temperature primary iodides need about 2.5 hours, primary bromides about 6 hours for complete reaction. With secondary halides it is advisable to add urea as this raises the solubility... 

A redox cyclopentadienyl iron moiety can also be introduced into the poly(vinyl chloride) backbone by a similar technique.Many other attempts were reported at replacing the halogens of poly(vinyl chloride), poly(vinyl bromide), and poly(vinyl iodide) with an alkali metal or with a hydrogen. For instance, in an effort to form poly(vinyl lithium), the polymers were reacted with organolithium compounds and with metallic lithium. The reactions with alkyllithium, however, resulted in substitutions by the alkyl groups, similarly to the reactions shown previously ... 

Formation of such complex compoimds, but already with alkali-metal halides, has foimd application in the manufacture of modern metal halide lamps (Bom et al., 2004 Hilpert and Niemann, 1997), which have an emission spectmm close to that of the natural sunlight. Relevant iodides and bromides (particularly cerium and dysprosium bromides and iodides) were foimd to be the most suitable components of binary compoimds for the production of lamp vessels from silica glass (Markus et al., 2005). Further technological developments led to the replacement of vessel material by polycrystalline alumina and to the use of rare-earth chlorides for improving lamp characteristics (Rutkowska et al., 2004). 

Redistilled water (for use if the distilled water available is not iodide-free). To 1,500 ml of distilled water in a 3-litre, round-bottomed distilling flask mounted on a shallow sand-bath, add 50 g of potassium carbonate and a few glass beads, connect the flask to a condenser with a ground-glass joint and distil. Discard the distillate until it is neutral to methyl red. If required successive 1,500-ml quantities can be distilled but the alkali should be replaced after 20 litres have been distilled. 

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