Iodide, free

Considerable challenges still remain in the development of new carbonylation processes for acetic acid manufacture. For example, all of the current processes use iodide compounds, leading to corrosive HI and the need for expensive materials for plant construction. An iodide-free system could potentially impart considerable benefit. Other long term goals include the selective direct conversion of syn-gas or oxidative carbonylation of methane to acetic acid. Organometallic chemists are certain to play a crucial role if these targets are to be achieved. 

Preparation of Nj5 Bromate Solution.—5-567 gms. (1/30 mol.) of potassium bromate are dissolved in water to 1,000 c.cs. 25 c.cs. are withdrawn, diluted to 200 c.cs. with water, 3—5 gms. of potassium bromide (free from bromate), 3—5 gms. potassium iodide (free from iodate) and 5 c.cs. cone, hydrochloric acid (free from chlorine or iron) added. The liberated iodine is titrated with thiosulphate in the usual way, and the bromine equivalent of the bromate solution thus obtained. 

Potassium Dichromate, 0.1 N (4.903 g K2Cr207 per 1000 mL) Dissolve about 5 g of potassium dichromate (K2Cr207) in 1000 mL of water, transfer quantitatively 25 mL of this solution to a 500-mL glass-stoppered flask, add 2 g of potassium iodide (free from iodate) (KI), dilute with 200 mL of water, add 5 mL of hydrochloric acid, and mix. Allow to stand for 10 min in a dark place, and titrate the liberated iodine with 0.1 N Sodium Thiosulfate, adding Starch TS as the endpoint is approached. Correct for a blank run on the same quantities of the same reagents, and calculate the normality. 

In order to prepare this solution, i part by weight of potassium iodide (free from iodine) is dissolved in 10 parts of water. The solution should be colourless and remain so when a few drops of dilute sulphuric or hydrochloric acid are added. 

The iodine is filtered off and purified by sublimation. The now iodide-free solution is then neutralized and reutilized for dissolving fresh niter. 

The estimation of free white phosphorus is carried out, as described on p. 137, and that of the other constituents by the usual methods. For the estimation of potassium chlorate, 0 5 g. of the composition is washed se eral times with 50 c.c. of water, a little potassium iodide (free from iodine) added, and one and a half times the volume of fuming hydrochloric acid. The whole is heated in a closed bottle for fifteen to twenty minutes on the steam bath, and when cold, the liberated iodine titrated with Nf o sodium thiosulphate. 

Unsaturated Products. The irradiated sample was condensed at 77 °K. An excess of a standard acid solution of bromate and bromide was added, and the temperature was raised. When the reaction was complete, the mixture was treated with excess iodide. Free iodine was titrated with thiosulfate. A blank analysis was substracted from the measured volume. 

Chaigneau reported the preparation of zirconium(IV) iodide in high yield by heating zirconium (IV) oxide with anhydrous aluminum iodide. A check of this method gave a moderate yield of zirconium (IV) iodide (free from aluminum)-... 

PROCEDURE Add 1 of solid CuS04 5H20 to a large, dry test tube. Add a circular filter paper spacer. Now add 2 of iodide-free NaCl and another spacer on top. Place two or three ungalvanized iron nails on top of the second spacer. Carefully, add water to cover the nails (ensure there are no entrapped bubbles). Leave undisturbed and observe the changes. No special precautions with respect to waste disposal need to be taken with this experiment/demonstration. 

Transfer the iodide-free/iodine-free aqueous solution to a 30-ml Erlenmeyer flask, add a small piece of platinum foil coated with platinum black to destroy the excess H2O2 and evaporate to about 2 ml. Make up the concentrated solution to about 30 ml with 4 m hydrochloric acid, transfer to a shaking funnel, add 1.0 ml of rhodamine B mixing reagent, mix and leave to stand for 25 minutes. 

Ethereal methyl-Li prepared from methyl iodide and Li, Mg added when the reaction is apparently complete, gently refluxed for 30 min., filtered, and excess of this methyl iodide-free soln. of methyl-Li warmed 15 min. with difluo-renylidene (prepn. s. 863), then washed with water 9-methyl-9,9 -difluorenyl. Y 80-90%.—If residual methyl iodide is not removed, 9,9 -dimethyl-9,9 -di-fluorenyl is obtained as a by-product. P. M. G. Bavin, Can. J. Chem. 38, 882 (1960). 

In its reactivity, iodomethylzinc iodide behaves as if it were a source of H2C , a species called methylene. It is not. Methylene belongs to a class of neutral molecules called carbenes, which contain a divalent carbon plus two unshared electrons that can be either paired or unpaired. A characteristic reaction of many carbenes is cycloaddition to double bonds to form cyclopropanes, a property that is shared by iodomethylzinc iodide. Free H2C is not involved in the Simmons-Smith reaction, but the similarity in behavior of iodomethylzinc iodide toward alkenes has led to referring to it and related compounds as carbenoids. 

Reagents All reagents should be iodide-free and of analytical reagent grade and redistilled water (or iodide-free distilled water) should be used in making up all solutions. 

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. 

A polystyryl iodide (PS-I Mn=1500 and My,/M =1.26) was used as an initiating adduct Po-X. The polymerization of styrene was carried out at 80° G with a fixed amount of Po-X (17 mM) and varying amounts of BPO (0-30 mM). The first-order plot of [M] was linear, indicating that the steady-state kinetics (eqn [21]) holds, in all examined cases. The values of (Rp/[M]) obtained from the first-order plot of [M] were linear in [BPO]o (filled circles in Figure 14(a)) and equal to those of the conventional (iodide-free) system (open circles in Figure 14(a)). This means that the iodide had no detectable effect on the polymerization rate. 

Yanagida S, Yu Y, Manseki K (2009) lodine/iodide-free dye-sensitized solar cells. Acc Chem Res 42(11) 1827-1838. doi 10.1021/ar900069p... 

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