Iodine-atom combination

The oxidation number of every halogen atom in its compounds is - 1 except for a chlorine, bromine, or iodine atom combined with oxygen or a halogen atom higher in the periodic table. For example, the chlorine atoms in each of the following compounds have oxidation numbers of -1 ... 

Iodine atoms combine to form molecular iodine in the gas phase... 

Iodine atoms combine to form I2 in liquid hexane solvent with a rate constant of 1.5 X 10 L/mol s. The reaction is second order in I. Since the reaction occurs so quickly, the only way to study the reaction is to create iodine atoms almost instantaneously, usually by photochemical decomposition of I2. Suppose a flash of light creates an initial [I] concentration of 0.0100 M. How long will it take for 95% of the newly created iodine atoms to recombine to form I2 ... 

Triethylborane in combination with oxygen provides an efficient and useful system for iodine atom abstraction from alkyl iodide, and thus is a good initiator for iodine atom transfer reactions [13,33,34]. Indeed, the ethyl radical, issued from the reaction of triethylborane with molecular oxygen, can abstract an iodine atom from the radical precursor to produce a radical R that enters into the chain process (Scheme 13). The iodine exchange is fast and efficient when R is more stable than the ethyl radical. 

Elimination of HI, which in the presence of an excess of IN3 can form hydrazoic acid, followed by its addition to the vinyl azides can give an intermediate triazide 75. The same compound could arise directly by substitution of one iodine atom by an azido group. The intermediate 75 has been considered to undergo a transannular reaction with homolytic cleavage of the weak C—I bond to form the radical 76, which loses a nitrogen atom to a radical 77. Combination of the two radicals leads to the 2-tetrazene 74 (equation 77). 

In the reaction of chlorine with potassium iodide, both Cl atoms in Cl2 gain an electron from an iodide ion, I, thus forming two chloride ions, Cl . The iodine atoms so formed, by the loss of an electron, combine to give an iodine molecule, I2. 

Hydrogen peroxide and organic hydroperoxides can be reduced by molybdate-activated iodide [Allen et al. 1952 reactions (13) and (14)]. The iodine atoms formed in these reactions combine to iodine which complexes with iodide [reactions (15) and (16)], and it is this I3- complex which is measured (s(3540 nm) = 25,000 dm3 mol-1 cm-1)... 

The chemical structures of thyroxine and triiodothyronine are shown in Figure 31—1. As shown in the figure, thyroid hormones are synthesized first by adding iodine to residues of the amino acid tyrosine. Addition of one iodine atom creates monoiodotyrosine, and the addition of a second iodine creates diiodotyrosine. Two of these iodinated tyrosines are then combined to complete the thyroid hormone. The combination of a monoiodotyrosine and a diiodotyrosine yields triiodothyronine, and the combination of two diiodoty-rosines yields thyroxine.55... 

FIGURE 31-1 Structure of the thyroid hormones triiodothyronine (T3] and thyroxine (T4X Addition of one iodine atom [I] to tyrosine produces monoiodotyrosine addition of a second iodine atom produces diiodotyrosine. A monoiodotyrosine and diiodotyrosine combine to form triiodothyronine (T3X Coupling of two diiodotyrosines forms thyroxine (T4X... 

But in this case, the weakness of the HI bond means that HI is not readily formed by attack of RH groups, instead the presence of R radicals can lead to combination with iodine atom through the reaction (Equation 4.7) 7... 

Diodo-l-alkenes.1 This reagent (1) in combination with a wide variety of nucleophiles reacts with 1-iodoalkynes to afford 2-substituted 1,1-diiodo-l-alkenes (2) in 50-85% yield. The products can be converted to a variety of alkenes by reaction of both the iodine atoms.2... 

The simplest iodoalkane, CH3I, has been studied repeatedly by MW and ED (Table 43). The re value for the C—I distance from a combined MW/IR investigation and the rg value which is reported in a recent ED analysis of the entire series of the iodomethanes CH I, n = 1 to 4, are in perfect agreement. The gas-phase studies for the methanes with two or more iodines were performed at 360 K for CH2I2, at 400 K for CHI3 and at 425 K for CI4. Within the combined experimental uncertainties the C—I bond distances remain constant for mono-, di- and triiodomethane and increases by ca 3 pm in carbon tetraiodide. As in the case of carbon tetrachloride and tetrabromide, this increased bond length in CI4 can be rationalized by steric repulsions between the iodine atoms. The large steric requirement of... 

The correct answer is (B). N, P, As, and Sb are all group 5 elements that can form three single bonds with fluorine to yield an octet. Iodine, a group 8 element, according to the octet rule, should only be able to combine with one fluorine atom. Combining with 3 is a violation of the octet rule. 

The only example of this type of compound is IF7. This is the result of several factors, among them the large size of the iodine atom and the easier oxidation of iodine to a +7 oxidation state. Also, the combination of iodine with fluorine represents the largest electronegativity difference possible for interhalogens. The compound is prepared by the reaction of fluorine with IF5 at elevated temperatures ... 

In the case where both processes can be studied for the same atom or ion (e.g., transfer from iodide ion to solvent and from solvent to iodine atom), the two cycles may be combined to give... 

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