Iodoform, preparation

Place 0 5 ml. of acetone, 20 ml. of 10% aqueous potassium iodide solution and 8 ml. of 10% aqueous sodium hydroxide solution in a 50 ml. conical flask, and then add 20 ml. of a freshly prepared molar solution of sodium hypochlorite. Well mix the contents of the flask, when the yellow iodoform will begin to separate almost immediately allow the mixture to stand at room temperature for 10 minutes, and then filter at the pump, wash with cold w ater, and drain thoroughly. Yield of Crude material, 1 4 g. Recrystallise the crude iodoform from methylated spirit. For this purpose, place the crude material in a 50 ml. round-bottomed flask fitted with a reflux water-condenser, add a small quantity of methylated spirit, and heat to boiling on a water-bath then add more methylated spirit cautiously down the condenser until all the iodoform has dissolved. Filter the hot solution through a fluted filter-paper directly into a small beaker or conical flask, and then cool in ice-water. The iodoform rapidly crystallises. Filter at the pump, drain thoroughly and dry. 

Iodoform reaction. To i ml. of the aldehyde solution, add 3 ml. of 10% KI solution and 10 ml. of freshly prepared sodium hypochlorite solution. Yellow crystals of iodoform, CHI3, soon separate. 

Methylene bromide (CHjBfj) and methylene iodide (CHjIj) are easily prepared by the reduction of bromoform or iodoform respectively with sodium arsenite in alkaline solution ... 

In a 1-litre three-necked flask, fitted with a mechanical stirrer, reflux condenser and a thermometer, place 200 g. of iodoform and half of a sodium arsenite solution, prepared from 54-5 g. of A.R. arsenious oxide, 107 g. of A.R. sodium hydroxide and 520 ml. of water. Start the stirrer and heat the flask until the thermometer reads 60-65° maintain the mixture at this temperature during the whole reaction (1). Run in the remainder of the sodium arsenite solution during the course of 15 minutes, and keep the reaction mixture at 60-65° for 1 hour in order to complete the reaction. AUow to cool to about 40-45° (2) and filter with suction from the small amount of solid impurities. Separate the lower layer from the filtrate, dry it with anhydrous calcium chloride, and distil the crude methylene iodide (131 g. this crude product is satisfactory for most purposes) under diminished pressure. Practically all passes over as a light straw-coloured (sometimes brown) liquid at 80°/25 mm. it melts at 6°. Some of the colour may be removed by shaking with silver powder. The small dark residue in the flask solidifies on cooling. 

Triiodoacetic acid [594-68-3] (I CCOOH), mol wt 437.74, C2HO2I3, mp 150°C (decomposition), is soluble in water, ethyl alcohol, and ethyl ether. It has been prepared by heating iodic acid and malonic acid in boiling water (63). Solutions of triiodoacetic acid are unstable as evidenced by the formation of iodine. Triiodoacetic acid decomposes when heated above room temperature to give iodine, iodoform, and carbon dioxide. The sodium and lead salts have been prepared. 

Methylene iodide [75-11-6], CH2I2, also known as diio dome thane, mol wt 267.87, 94.76% I, mp 6.0°C, and bp 181°C, is a very heavy colorless Hquid. It has a density of 3.325 g/mL at 20°C and a refractive index of 1.7538 at 4°C. It darkens in contact with air, moisture, and light. Its solubiHty in water is 1.42 g/100 g H2O at 20°C it is soluble in alcohol, chloroform, ben2ene, and ether. Methylene iodide is prepared by reaction of sodium arsenite and iodoform with sodium hydroxide reaction of iodine, sodium ethoxide, and hydroiodic acid on iodoform the oxidation of iodoacetic acid with potassium persulfate and by reaction of potassium iodide and methylene chloride (124,125). Diiodoform is used for determining the density and refractive index of minerals. It is also used as a starting material in the manufacture of x-ray contrast media and other synthetic pharmaceuticals (qv). 

Bismuth subnitrate [1304-85-4] (basic bismuth nitrate) can be prepared by the partial hydrolysis of the normal nitrate with boiling water. It has been used as an antacid and in combination with iodoform as a wound dressing (183). Taken internally, the subnitrate may cause fatal nitrite poisoning because of the reduction of the nitrate ion by intestinal bacteria. 

At 225—275°C, bromination of the vapor yields bromochloromethanes CCl Br, CCl2Br2, and CClBr. Chloroform reacts with aluminum bromide to form bromoform, CHBr. Chloroform cannot be direcdy fluorinated with elementary flourine fluoroform, CHF, is produced from chloroform by reaction with hydrogen fluoride in the presence of a metallic fluoride catalyst (8). It is also a coproduct of monochlorodifluoromethane from the HF—CHCl reaction over antimony chlorofluoride. Iodine gives a characteristic purple solution in chloroform but does not react even at the boiling point. Iodoform, CHI, may be produced from chloroform by reaction with ethyl iodide in the presence of aluminum chloride however, this is not the route normally used for its preparation. 

Cormier and Dure (1963) found another type of luciferin and called it protein-free luciferin. Protein-free luciferin was found in the vapor condensate of freeze-drying whole animals, and also in the 3 5-56 % ammonium sulfate fraction of the crude extract noted above. The protein-free luciferin behaved like an aromatic or heterocyclic compound and it was strongly adsorbed onto Sephadex and other chromatography media, requiring a considerable amount of solvent to elute it. The luminescence reaction of protein-free luciferin in the presence of luciferase required a 500-times higher concentration of H2O2 compared with the standard luciferin preparation. Both types of the luciferin preparation had a strong odor of iodoform. 

Bromo- and iodocyclopropanes cannot be prepared by the direct halogenation of cyclopropanes. Substituted chloro- and bromocyclopropanes have been synthesized by the photochemical decomposition of a-halodiazomethanes in the presence of olefins iodocyclopropanes have been prepared from the reaction of an olefin, iodoform and potassium f-butoxide followed by the reduction of diiodocyclopropane formed with tri-w-butyl tin hydride. The method described employs a readily available light source and common laboratory equipment, and is relatively safe to carry out. The method is adaptable for the preparation of bromo- and chlorocyclopropanes as well by using bromodiiodomethane or chlorodiiodomethane instead of iodoform. If the olefin used will give two isomeric halocyclopropanes, the isomers are usually separable by chromatography. ... 

Alternatively, the use of the reagent prepared by mixing trifluoroethanol, diethylzinc and iodoform led to the formation of the corresponding iodocyclopropane with outstanding diastereocontrol (equation 62). 

Bis(iodozincio)iodomethane was prepared from diethylzinc and iodoform as shown in equation 54 by Charette and coworkers78. This prepared bis(iodozincio)iodomethane possesses both a carbenoid and a gem-dimetal species, and therefore reacts as a zinciomethyl carbenoid. 

Iodine is used in various forms in medicine—e.g. tincture of iodine, liquor iodi, iodized cotton, iodized wine, iodized water, oils and syrups iodides of potassium, mercury, iron, arsenic, lead, etc. and as methyl iodide or di-iodide iodoform, CHI3 ethyl iodide, C2H5I iodole, C4I4.NH aristole etc.—largely for external application as an antiseptic. Some iodides are used in photography, and in analytical operations and a considerable amount of iodine is used in the preparation of aniline dyes. 

Three common methods of production are described in the literature the action of iodine,1 sodium ethylate,2 or hydriodic acid 3 on iodoform. The last of these three methods has been worked out in more detail and is the one generally recommended for the preparation of methylene iodide in the laboratory. In addition, methylene iodide has been produced by the action of iodine on diazomethane 4 and by electrolysis of iodoacetic acid.5 It may also be made by the action of potassium iodide upon methylene chloride.Sa... 

The reduction of iodoform by means of sodium arsenite,6 described both by V. Auger and A. Gutmann, gave such successful results that the other methods were disregarded. The reaction is extremely simple and in the course of a few hours several pounds of pure methylene iodide may be prepared. 

Aloe latex is prepared by cutting transversely the leaf near the base and kept in an inclined position so that the latex contained in the specialized pericyclic cells, and sometimes in the adjacent parenchyma, flows out in about 6 h. No pressure must be applied or the product will be contaminated with the mucilage present in the inner part of the leaves. The latex obtained is bitter and yellow condensed to dryness, it becomes a shiny mass, similar to broken glass, of a yellowish green to red-black color. Slow evaporation, carried out at an inappropriate temperature, yields an opaque mass with a waxlike fracture. The taste is nauseating and bitter, and the odor sour, recalling that of rhubarb, apple-tart, or iodoform (Sollmann, 1944). 

Iodoform test. Place 5 drops of each sample into separate clean, dry test tubes (150 X 18 mm). Add to each test tube 2mL of water. If the compound is not soluble, add dioxane (dropwise) until the solution is homogeneous. Add to each test tube (dropwise) 2mL of 6 M NaOH tap the test tube with your finger to mix. The mixture is warmed in a 60°C water bath, and the prepared solution of I2-KI test reagent is added dropwise (with shaking) until the solution becomes brown (approximately 25 drops). 

Iodoform from Ethyl Alcohol.—Chloroform and bromoform cannot be prepared electrolytically from alcohol (Elbs and Herz4). This is contrary to the claims of the I). R. P. No. 

Coughlin 1 has. substantially verified the results of Elbs in the case of bromoform. He obtained only small quantities of this body which can be easily prepared electro-lytically from acetone. The formation of iodoform, on the contrary, takes place smoothly. It is obtained technically according to the above-mentioned patent. Elbs and Herz have established the following conditions for this reaction. 

The reaction is the same as that involved in the usual chemical preparation of iodoform, whereby a colorless solution of hypoiodite (obtained by dissolving iodine in a sufficient quantity of potassium-hydroxide solution) is made to react with alcohol. The decomposition potential of potassium iodide, investigated by Dony-Henault,2 show s that the iodine as such does not act on the alcohol, but only after its conversion into hypoiodite. The iodine ions are set free at the same anode potential no matter if alcohol is added or not. The alcohol does not act as a depolarizer towards the iodine ion the electrical iodoform synthesis is a typical secondary process. 

Although the substitution processes afforded by the action of the primarily discharged anion of an inorganic salt upon an organic body are to be included among the simpler reactions, the results obtained so far in this domain have been very scanty, especially in regard to aromatic substances. The above-mentioned investigations of Elbs and Hertz, as well as those of Forster and Mewes on the electrolytic preparation of iodoform,... 

---