Iodine monochloride iodinating agent

Molecular iodine is not a very powerful halogenating agent. Only very reactive aromatics such as anilines or phenolate anions are reactive toward iodine. Iodine monochloride can be used as an iodinating agent. The greater electronegativity of the... 

Such anti-MarkownikofT regioselectivity may be achieved in the formation of iodides by proceeding via the corresponding organoborane, which is then decomposed with iodine in the presence of sodium methoxide93 (Expt 5.66). More recently iodine monochloride has been found to be an economic alternative iodinating agent.94... 

Therefore from kinetic data of this type, not even the reactive species of the iodinating agent can be specified, and, in consequence, nothing can be said with respect to the mechanism of the substitution proper. Berliner (1958) drew the same conclusion from his investigations on the iodination of 2,4-dichlorophenol and anisole with iodine monochloride. 

The iodinating agent in our procedure is iodine monochloride, ICl. Because iodine is the less electronegative of the two halogens, this reagent is polarized to make the iodine atom electrophilic, and it may dissociate to give Cl and H. The electrophile for the reaction is thus either polarized molecular I-Cl or iodonium ion... 

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. 

Iodine can, however, be displaced cleanly with bromine<150) and with chlorine if iodine monochloride or sulfuryl chloride and benzoyl peroxide are used as chlorinating agents.reactivity ratios for the displacement of bromine by chlorine from substituted bromo-benzenes have been found to be in the order p-phenyl > o-methoxy > p-chloro > un-... 

The synthesis of ionic triiodinated contrast agents starts from either bisamino nitrophthalic acid or amino isophthalic acid. The nitro group is reduced to the amino moiety by hydrogenation. Iodine is introduced in aqueous solution with iodine monochloride. Due to the decrease in solubiHty the resulting triiodobenzene precipitates from the solution and can be recrystallised. Amino functions are then acylated. 

The halogenation of a wide variety of aromatic compounds proceeds readily in the presence of ferric chloride, aluminum chloride, and related Friedel-Crafts catalysts. Halogenating agents generally used are elemental chlorine, bromine, or iodine and interhalogen compounds (such as iodine monochloride, bromine monochloride, etc.). These reactions were reviewed554 and are outside the scope of the present discussion. 

Of all the methods described for the synthesis of thiazole compounds, the most efficient involves the condensation of equimolar quantities of thiourea and a-halo ketones or aldehydes to yield the corresponding 2-aminothiazoles (Scheme 167) (l888LA(249)3l). The reaction occurs more readily than that of thioamides and can be carried out in aqueous or alcoholic solution, even in a distinctly acid medium, an advantage not shared by thioamides which are often unstable in acids. The yields are usually excellent. A derived method condenses the thiourea (2 mol) with the non-halogenated methylene ketone (1 mol) in the presence of iodine (1 mol) or another oxidizing agent (chlorine, bromine, sulfuryl chloride, chlorosulfonic acid or sulfur monochloride) (Scheme 168) (45JA2242). 

The iodine monochloride is an ideal reagent except for the necessity of its handling or preparation. This difficulty has been overcome by the reaction of organoboranes with iodide ion in the presence of mild oxidizing agent chloramine-T 177). The reaction proceeds under extremely mild conditions to afford the corresponding alkenyl iodides (Eq. 115)178) where it can tolerate a variety of functional groups. 

When free iodine forms during the course of a titration, even though a reducing agent is present, it can be regarded as resulting from the further reduction of the iodine monochloride complex ... 

ICI2- -f 2e" I2 + 4Cr E° = 1.06 V (20-4) When all the reducing agent has been consumed, the free iodine is titrated to form the iodine monochloride complex ... 

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