Iodide oxidation solvent dependence

Chlorine trifluoride is one of the most powerful fluorinating agents particularly useful for the oxidation of perfluoroalkyl iodides to the corresponding perfluoroalkyliodine(III) difluorides and perfluoroalkyliodine(V) tetrafluorides.113,17 The reactions are conducted at — 78 to 20 °C in perfluorohexane or without solvent. Depending on the stoichiometric amount of chlorine trifluoride, the products are RfIF2 or RfIF4. 

With secondary and tertiary alkyl halides an Ea-elimination is often observed as a side-reaction. As the alkyl halide reactant an iodide is most often employed, since alkyl iodides are more reactive than the corresponding bromides or chlorides. With phenoxides as nucleophiles a C-alkylation can take place as a competing reaction. The ratio of 0-alkylation versus C-alkylation strongly depends on the solvent used. For example reaction of benzylbromide 4 with /3-naphth-oxide 5 in yV,A-dimethylformamide (DMF) as solvent yields almost exclusively the /3-naphthyl benzylether 6, while the reaction in water as solvent leads via intermediate 7 to formation of the C-benzylated product—l-benzyl-2-naphthol 8—as the major product ... 

Polarographic evidence is available on the anodic wave due to oxidation of the iodide ion in various EPD solvents in the presence of an excess of cadmium ions that function as EPA 20). The extent of interaction depends on the EPD properties of the solvent competing with the iodide ions for coordination with the cadmium ions. The EPA properties of the cadmium ion are decreased by an increase in the donicity of the solvent thus it is clear that redox potentials in different solvents are related to its donicity. The stabilization of the iodide ion by cadmium ions increases with decreasing donicity and the redox potential shifts to more positive values 20). 

The kinetics of the reaction of solid sodium iodide with 1-bromooctane were studied with a 95 % RS graft of polyethylene oxide) 6-mer methyl ether on 3 % CL polystyrene as catalyst (51)176). The rates were approximately first order in 1-bromooctane and independent of the amount of excess sodium iodide. The rates varied with the amount of the solid catalyst used, but there was not enough data to establish the exact functional dependence. All experiments employed powdered sodium iodide, magnetic stirring, and 75-150 pm catalyst beads. Thus the variables stirring speed and particle size, which normally are affected by mass transfer and intraparticle diffusion, were not studied. Yanagida 177) favors a mechanism of transfer of the sodium iodide by dissolution in the solvent (benzene) and diffusion to the catalyst particle... 

Over the past few years, it has been shown that the electroreduction of NiLn complexes is feasible in various solvents (DMF, acetonitrile, THF,. ..) at potential values depending on the nature of both solvent and ligand. The electroformed species reacts by oxidative addition with halogenated derivatives including organic halides (iodide, bromide, chloride) (equation 27). 

The efficiency of the extraction depends on the coordinating ability of the solvent, and on the acidity of the aqueous solution which determines the concentration of the metal complex. Coordinating ability follows the sequence ketones > esters > alcohols > ethers. Many metals can be extracted as fluoride, chloride, bromide, iodide or thiocyanate complexes. Table 4.5 shows how the extraction of some metals as their chloro complexes into diethyl ether varies with acid concentration. By controlling acidity and oxidation-state and choosing the appropriate solvent, useful separations can be achieved. As, for example, the number of readily formed fluoride complexes is small compared. with those involving chloride, it is evident that a measure of selectivity is introduced by proper choice of the complexing ion. The order of selectivity is F > Br > I" > Cl" > SCN". Examples of oxonium systems are included in tabic 4.4. 

Iodine Monochloride This precursor is generated by the exchange IGl/Na I, which corresponds to an oxidation of iodide by cold iodine. It can also be obtained by oxidation with elemental GI2. Depending on the reaction conditions, pH, and solvent, the reagent is either IO or IOH and lOHj, respectively, in basic and acidic media. 

Chemical Properties of Thiazolidines.—Alkylation of metal salts of thiazolidine-2-thione can yield either TV-alkyl derivatives, depending on the type of solvent, the alkylating agent, and the counter-ion e.g., the sodium salt with methyl iodide in dioxan gives mainly the 5-methyl compound, whilst with dimethyl sulphate in DMSO the N-methyl derivative is obtained. Oxidative imination of the thiazolidin-4-one (82), using Chloramine-T, gives (83) quantitatively, whilst... 

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