Iodination s. Halogenation

In addition to the classic triad Mendeleev predicted the existence of other unknown elements. On the whole, as early as 1870 Mendeleev saw about ten vacant places in his table. He saw fhem, for instance, in the seventh group where there were neither manganese analogues nor a heavy iodine s analogue (the heaviest halogen which had to possess metallic properties). 

Mixtures of halogen and halogen polyfluorides are effective sources of the corresponding halogen monofluorides in reactions with fluoroolefins.—E Deca-fluorocyclohexene shaken 26 hrs. at 265° with bromine trifluoride and bromine in an autoclave bromoundecafluorocyclohexane. Y 78%. F. e., also with iodine pentafluoride/iodine, s. R. D. Ghambers, W. K. R. Musgrave, and J. Savory, Soc. 1961, 3779. 

Iodine monochloride [7790-99-0] ICl, mol wt 162.38, 78.16% I, is a black crystalline soHd or a reddish brown Hquid. SoHd ICl exists ia two crystalline modifications the a-form, as stable mby-red needles, d = 3.86 g/mL and mp 27.3°C and as metastable brownish red platelets, d = 3.66 g/mL, mp 13.9°C and bp 100°C (dec). Iodine monochloride is used as a halogenation catalyst and as an analytical reagent (Wij s solution) to determine iodine values of fats and oils (see Fats and fatty oils). ICl is prepared by direct reaction of iodine and Hquid chlorine. Aqueous solutions ate obtained by treating a suspension of iodine ia moderately strong hydrochloric acid with chlorine gas or iodic acid (118,119). 

Rates of enolization can be measured in several wt s. One method involves determining the rate of halogenation of the ketone. In the presence of a sufficient concentration of bromine or iodine, halogenation is much faster than enolu ation or its reverse and can therefore serve to measure the rate of enolization ... 

Of the four halogens, iodine is the weakest oxidizing agent. Tincture of iodine, a 10% solution of I2 in alcohol, is sometimes used as an antiseptic. Hospitals most often use a product called povidone-iodine, a quite powerful iodine-containing antiseptic and disinfectant, which can be diluted with water to the desired strength. These applications of molecular iodine should not delude you into thinking that the solid is harmless. On the contrary, if I2(s) is allowed to remain in contact with your skin, it can cause painful bums that are slow to heal. 

Now let s slide to the left in the periodic table and consider the column of elements fluorine, chlorine, bromine, iodine, and astatine. Each of these elements has one less electron than does its neighboring inert gas. These elements are called the halogens. (The discussion that follows does not include astatine because this halogen is very rare.)... 

The first column of the periodic table, Group 1, contains elements that are soft, shiny solids. These alkali metals include lithium, sodium, potassium, mbidium, and cesium. At the other end of the table, fluorine, chlorine, bromine, iodine, and astatine appear in the next-to-last column. These are the halogens, or Group 17 elements. These four elements exist as diatomic molecules, so their formulas have the form X2 A sample of chlorine appears in Figure EV. Each alkali metal combines with any of the halogens in a 1 1 ratio to form a white crystalline solid. The general formula of these compounds s, AX, where A represents the alkali metal and X represents the halogen A X = N a C 1, LiBr, CsBr, KI, etc.). 

Chlorine and iodine have been used extensively since their introduction as disinfecting agents in the early 19th century. Preparations containing these halogens such as Dakin s solution and tincture of iodine were early inclusions in many pharmacopoeiae and national formularies. More recent formulations of these elemens have improved activity, stability and ease of use. 

Attempts to oxidise silver dithiocarbamato complexes with halogens to compounds with the metal in higher oxidation states obviously failed. By addition of iodine to a solution of [Ag(Bu2 fc)]g in CHQ3, an insoluble product is formed with the composition rjA% S> X2dtc) 141). With other alkyl groups similar complexes are obtained. Investigations about the nature of this type of compounds are in progress. 

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