Addition of iodine

The halogen in the 5-position of 2-aminothiazoles is usually reactive and is used for further reaction (see Chapter V). The reaction may take place in the same medium as thiocyanation (437-440), rhodanation (441). or reaction with NaNO (435). Similarly, a mixture of 2-amino-4-methylthiazole and thiourea in H2O yields 5,5 -thiobis(2-amino-4-methyDthiazole (202) after addition of iodine (Scheme 128) (442). 

The enrichment program followed in the United States is (/) the enrichment of flour, bread, and degerminated and white rice using thiamin [59-43-8] C 2H y N O S, riboflavin [83-88-5] C2yH2QN4Na02P, niacin [59-67-6] CgH N02, and iron [7439-89-6]-, (2) the retention or restoration of thiamin, riboflavin, niacin, and iron in processed food cereals (J) the addition of vitamin D [67-97-0] to milk, fluid skimmed milk, and nonfat dry milk (4) the addition of vitamin A [68-26-8], C2qH2qO, to margarine, fluid skimmed milk, and nonfat dry milk (5) the addition of iodine [7553-56-2] to table salt and (6) the addition of fluoride [16984-48-8] to areas in which the water supply has a low fluoride content (74). 

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. 

Magnesium iodide is soluble in alcohols and many other organic solvents, and forms numerous addition compounds with alcohols, ethers, aldehydes, esters, and amines. One example is magnesium iodide dietherate [29964-67-8], Mgl2 prepared by gradual addition of iodine to a... 

Sodium a2idodithiocarbonate decomposes with evolution of nitrogen gas on addition of iodine, thus providing a useful quaHtative test for the presence of residual carbon disulfide ia aqueous solutions (25). 

There have also been relatively few mechanistic studies of the addition of iodine. One significant feature of iodination is that it is easily reversible, even in the presence of excess alkene. The addition is stereospecifically anti, but it is not entirely clear whether a polar or a radical mechanism is involved. ... 

Perfluoroalkylalkynes undergo unidirectional syn addition of iodine cyanide [M] (equation 43)... 

H R = Br) [85JCS(D)973] containing a rhodium-rhodium brmd. Each rhodium atom is octahedrally coordinated. Addition of iodine to 176 (E =... 

In the estimation of carvacrol a slight modification of this method must be made, because carvacrol is thrown down as a finely divided white precipitate, giving the solution a milky appearance. In order to form a precipitate the liquid is vigorously shaken after the addition of iodine solution, and is subsequently filtered. Then the liquid is acidulated with hydrochloric acid, and subsequently the same procedure is followed as was described for thymol. The calculation is also the same. 

The reaction generally starts without addition of iodine as an initiator, but the use of a crystal of iodine (no stirring) may occasionally be necessary with old magnesium or insufficiently... 

Potassium iodide is added as a nutrient to prevent goiter, a thyroid problem caused by lack of iodine, and to prevent a form of mental retardation associated with iodine deficiency. A project started by the Michigan State Medical Society in 1924 promoted the addition of iodine to table salt, and by the mid-1950s three-quarters of U.S. households used only iodized salt. Potassium iodide makes up 0.06 percent to 0.01 percent of table salt by weight. Sometimes cuprous iodide—iodide of copper—is used instead as the source of iodine. 

Fluoroalkanephosphonic acid can be obtained by addition of iodine perfluoroalkane to vinylphosphonic acid dichloride followed by saponification and deiodination by sodium amalgam [141]. Fluoroalkanephosphonic acids can be transformed to fluoroalkanephosphonic acid glycil esters by 2 mol of epi-chlorhydrin in a water-free solution followed by reaction with alkalines or amines [142]. Compounds of this kind with an alkyl chain of 8-20 carbon at-... 

Elimination of vinyl groups, [14] addition of iodine to double bonds, ester cleavage detection by IR... 

In a similar procedure for the preparation of iodotrimethyl-silane, aluminum, iodine, and hexamethyldisiloxane are combined, and the mixture is heated to reflux. When this procedure was attempted by the submitters, violent exothermic reactions occurred at ca. 50-60°. The slow addition of iodine to the warm mixture described in the present procedure leads to a controlled, reproducible reaction. 

The XMn(CO)5 system (48) is represented in Table X. Here it was concluded that the last step in formation of IMn(CO)5 is addition of a carbonyl, while in the formation of I Mn(CO)j the last step seems to be addition of iodine. 

The amino acid tyrosine is the starting point in the synthesis of the catecholamines and of the thyroid hormones tetraiodothyronine (thyroxine T4) and triiodothyronine (T3) (Figure 42-2). T3 and T4 are unique in that they require the addition of iodine (as T) for bioactivity. Because dietary iodine is very scarce in many parts of the world, an intricate mechanism for accumulating and retaining T has evolved. 

Oxidative-addition of iodine also was investigated for the complex C -bzimAu]3. This complex behaves like most of the CTCs since it adds iodine at only one gold center to yield [p,-N, C -bzimAu]3l2 [59]. The X-ray structure shows that it consists of discrete trinuclear units with the three gold atoms bridged by 1 -benzylimidazolates. 

Attempts to oxidise silver dithiocarbamato complexes with halogens to compounds with the metal in higher oxidation states obviously failed. By addition of iodine to a solution of [Ag(Bu2 fc)]g in CHQ3, an insoluble product is formed with the composition rjA% S> X2dtc) 141). With other alkyl groups similar complexes are obtained. Investigations about the nature of this type of compounds are in progress. 

Addition of iodine to alkenes can be accomplished by a photochemically initiated reaction. Elimination of iodine is catalyzed by excess iodine, but the diiodo compounds can be obtained if unreacted iodine is removed.52... 

The compounds [Au3Ira(MeN=COMe)3] ( = 2, 4, 6) obtained by stepwise addition of iodine to the cyclic tetranuclear gold(I) complexes [Au3(MeN=COMe)3] have been revisited. The structure of [Au3I6(MeN=COMe)3] (338) consists of columns of the molecular units united by weak iodine- iodine interactions which range in length from 3.636(2) A to 3.716(2) A. The solid-state molecular packing of the di-iodo and tetra-iodo complexes reveal no unusual features.1971... 

By oxidizing benzoin in methyl alcoholic sodium methoxide solution by the addition of iodine. Corson and McAllister, J. Am. Chem. Soc. 51, 2822 (1929). 

Tyrosine may be targeted specifically for modification through its phenolate anion by acylation, through electrophilic reactions such as the addition of iodine or diazonium ions, and by Mannich condensation reactions. The electrophilic substitution reactions on tyrosine s ring all occur at the ortho position to the —OH group (Figure 1.11). Most of these reactions proceed effectively only when tyrosine s ring is ionized to the phenolate anion form. 

The result of iodination at tyrosine groups can alter the spectral characteristics of the protein in solution (Hughes, 1950). The typical protein absorbency at 280 nm can shift to a maximum at about 305-315 nm due to the addition of iodine atoms to the phenolate ring of tyrosine. The degree of absorbance shift is dependent on how many iodine atoms are incorporated into the protein and whether they result in mainly mono- or di-iodotyrosine formation. In addition, as the level of iodination increases, the solubility of a protein in aqueous solution can dramatically decrease until complete insolubility results in proteins with high numbers of tyrosines. 

More importantly, the addition of iodine makes it possible to operate the filament at a hotter temperature, with a higher proportion of the emitted light being visible light, although we still form much heat. 

Fuchigami and co-workers showed that a-fluoroallenyl sulfide 302 can be smoothly converted into ( )-configured vinyl iodide 320 by addition of iodine in di-chloromethane at ambient temperature (Scheme 8.87) [166]. Ma et al. [176] treated... 

The addition of iodine electrophiles, fert-butyl hypoiodite (t-BuOI) in the presence of BF3, acetyl hypoiodite (AcOI), iodine monochloride (IC1) and iodine monobromide (IBr), to 1,3-butadiene gives always, under ionic conditions, mixtures of 1,2- and 1,4-Markovnikov adducts (equation 57). These mixtures are the kinetic products, since rearrangement to the thermodynamically stable products occurs under the appropriate conditions86. 

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