Iodine reaction- -alkali metals

Attempts to halogenate sp3-alkalimetal compounds in many cases lead to the formation of dimeric products as a consequence of a very fast subsequent reaction of the organometallic compound with the halogen derivative initially formed. Effective suppression of this reaction is only possible in conversions of less strongly basic organometallic compounds (e.g., enolates) with iodine the alkali-metal compound has to be added to the strongly cooled solution of iodine in Et20 or THF. 

Nickel carbonyl charged, or formed in the carbonylation reaction mixture, can catalyze the carbonylation of methanol (11). To maintain the activity of the nickel carbonyl catalyst high temperature and pressure are required (12-14). However, certain promoters can maintain an active, soluble, nickel carbonyl species under much milder conditions. The most reactive promoters are phosphines, alkali metal salts, tin compounds, and 2-hydroxypyridine. Reaction rates of 2 to 7 X 10-3(mol/1.sec) can be achieved without the use of high concentration of iodine (Table II). in addition, high reaction rates... 

Iodine dissolves without reaction in concentrated sulfuric acid and with concentrated nitric acid it reacts to form iodine pentoxide (47). Iodine reacts with alkali metal hydroxide solutions to form the corresponding hypoiodite and the rate of the reaction increases with the alkali concentration and temperature. At 50°C, the reaction is almost instantaneous ... 

Bismuth(III) iodide has been prepared in the absence of solvents by the reaction of iodine with elemental bismuth1,2 or with bismuth (III) sulfide.3 Alternative methods involve precipitation of bismuth(III) iodide from aqueous solutions of bismuth salts by adding alkali-metal iodides,4 and the addition of bismuth (III) oxide to a solution of iodine and tin(II) chloride in saturated hydrogen chloride.5 In either case the initial product is purified by sublimation, usually in an atmosphere of carbon dioxide. The product obtained by precipitation requires several resublimations for complete purification.6... 

The trend in oxidation potentials may be considered a composite trend, similar to that described for the E° values of the alkali metals (Chap. 6). For the halogens, the following quantities are involved heats of dissociation of the molecules, electron affinities of the atoms, hydration energies of the ions, heats of vaporization (for bromine and iodine only), and, finally, entropy or randomness effects. Aside from the entropy effects (which turn out to be quite small for the reactions being considered), the reduction of the halogen X to the hydrated ion X at room temperature may be represented in steps as follows ... 

The (-l-)-neomenthylcyclopentadienyllanthanide complexes Cp LnX2(THF)3 [X = Cl, Ln = Sm, Gd, Yb, Y, Lu X = I, Ln = Sm, Yb Cp = (-l-)-neomenthylcyclopenta-dienyl] were prepared by reaction of LnCls with appropriate alkali metal cyclopentadienyl derivatives. In the solid state, the monomeric Cp Sml2(THF)3 adopts a pseudo-octahedral geometry with the two iodine atoms taking trans positions. A similar structure is found for (Ind)GdCl2(THF)3. 

The first step of the reaction involves iodination of the aromatic compound with the triiodide salt in the presence of water as a solvent. The water should contain from 0.7 to 1.25 molar equivalents of a hydroxide, preferably an alkali metal hydroxide, and from 1-2 molar-equivalents of an alkali metal triiodide (e.g. iodine plus sodium iodide). The aqueous solvent should also contain from 0.1 to 20 mole % of an acid catalyst, which may be a mineral acid such as sulfuric, hydrochloric or phosphoric acid. Reaction is carried out at temperatures ranging from 20°-120° C. If the starting compound contains a nuclear substituent, iodination will occur in the ortho or para position on the nuclear ring. 

The subsequent step of the reaction, hydroxylation, is carried out directly with the reaction mixture from iodination without any interme diate isolation or other processing of the reactants or by-products. Abase, such as an alkali metal hydroxide or a quaternary amine such as tetraalkylammonium hydroxide, is added directly to the reaction mixture to make a final concentration of 0.5 to 6 molar, with 0.1 to 20 mole % copper metal, or cuprous salts such as oxide, chloride or iodide, at temperatures of from 50°-120° C. The preferred conditions art-addition of sodium hydroxide to the iodination reaction mixture to give a concentration of 2-5 molar, then addition of 1-5 mole % copper dust, cuprous oxide or cuprous chloride, then allowing reaction at reflux (100°-120° C.) for about 18 hours. 

The catalysts used are bromine, iodine, haloamides I and/or polymerization inhibitors, in general in amounts of from 0.0001 to 0.1 preferably from 0.001 to 0.05, mole of catalyst per mole of methyi ketone. Instead of the above catalysts, it is also possible to usr compounds which form such catalysts under the reaction conditions, e.g to use bromides and iodides in place of bromine or iodine. Water-soluble halides are preferred and are advantageously used in the form of thei alkaline earth metal salts or, especially, their alkali metal salts, e.g calcium bromide, calcium iodide, magnesium bromide, magnesiais iodide, lithium bromide, lithium iodide and especially sodium bromide or iodide or potassium bromide or iodide... 

---