Hydrogen iodine

This equilibrium is established when hydrogen iodide is heated, hydrogen-iodine bonds being broken. 

The reaction with fluorine occurs spontaneously and explosively, even in the dark at low temperatures. This hydrogen—fluorine reaction is of interest in rocket propellant systems (99—102) (see Explosives and propellants, propellants). The reactions with chlorine and bromine are radical-chain reactions initiated by heat or radiation (103—105). The hydrogen-iodine reaction can be carried out thermally or catalyticaHy (106). 

Absorption spectra of formazans have been studied in detail. Almost all formazans exhibit UV/visible spectra between 300 and 600 nm.1,2,12,13,40,62,325 326 The absorption maxima are very sensitive to substituent effects. For example, the 1,5-diphenyl formazan 185 when X is hydrogen, methyl, phenyl, cyano, and mercapto shows a band at 420, 410, 470, 504, and 590nm in ethanol, respectively. The 3-chloro derivative 186 when X is hydrogen, iodine, bromine, chlorine, and fluorine has a band at 433,433,430,421, and 417 nm, respectively. Table 13 shows the influence of substituents on the absorption maxima in the trisubstituted formazans 3. Table 14 shows the influence of substituents on the absorption maxima of... 

Fluorine Hydrogen, or Hydrogen, Oxygen Fluorine perchlorate Hydrogen Iodine heptafluoride Carbon, etc. 

Hydrogen-iodine reaction, 13 770 Hydrogen-ion activity, 14 23-34 nonaqueous solvents, 14 32 pH determination, 14 24-27 pH measurement systems, 14 27-31 Hydrogen ion concentration (total acidity), 14 23... 

The most frequently occurring simultaneous, interdependent reaction mechanism is the case in which the product, as its concentration is increased, begins to dissociate into the reactants. The classical example is the hydrogen-iodine reaction ... 

The synthesis of ionic triiodinated contrast agents starts from either bisamino nitrophthalic acid or amino isophthalic acid. The nitro group is reduced to the amino moiety by hydrogenation. Iodine is introduced in aqueous solution with iodine monochloride. Due to the decrease in solubiHty the resulting triiodobenzene precipitates from the solution and can be recrystallised. Amino functions are then acylated. 

For many years the hydrogen-iodine reaction was quoted in textbooks as being virtually the only known example of a simple bimolecular reaction. There is now evidence 43 that in parallel to the main bimolecular transformation, some additional reactions involving iodine atoms do occur. 

Whereas in the hydrogen-iodine reaction, atomic iodine plays only a minor part, in the reaction between hydrogen and bromine, bromine and hydrogen atoms are the principal intermediates in the overall transformation. 

The kinetics of the reaction are quite different from those of the hydrogen-iodine reaction although the stoichiometric equation ... 

Hydrogen bromide Hydrogen fluoride Hydrogen iodine... 

Hydrogen chloride Hydrogen iodine Hydrogen sulfide... 

A classical example of a process that follows the mechanism of (21) is the hydrogen-iodine reaction H2 + l2 2HI. If = 0 and = = Cq at t = 0 for this bimolecular process, then equation (22) becomes... 

The fact that the rate of decorriposition of pure hydrogen iodide and the rate of interaction of pure hydrogen and pure iodine gas are such that their ratio is equal to the equilibrium constant for the reaction between hydrogen, iodine, and hydriodic acid suggests strongly that at equilibrium both the forward and the... 

The hydrogen-iodine reaction is a classic in chemical kinetics. The work of Bodenstein on this reaction is one of the first systematic studies of the temperature dependence of reaction rates. For many years the formation of HI from H2 and I2 was regarded as the textbook example of a bimolecular four-center reaction as was its reverse. Recently, however, experimental results inconsistent with this interpretation have been obtained. ... 

While this work is requiring the revision of many textbooks which have used the hydrogen-iodine reaction as a classic example of a bimolecular reaction, it has also aroused interest in its implications for absolute reaction rate theory. Noyes has suggested that the results present a paradox in kinetics. In his discussion, he suggests that absolute rate theory as normally formulated fails to account for momentum effects which in some cases, namely the H2-I2 reaction, place severe restrictions on the path leading from reactants to products. In the... 

The hydrogen-bromine reaction is a classic example of a free radical reaction having been shown by Bodenstein et al. to have a much different kinetic behavior from the hydrogen-iodine reaction. Kassel has reviewed critically the early work. Other more recent reviews have also appeared ... 

If the hydrogen-iodine and the nitric oxide oxidation reactions did indeed result simply from the collision of the molecular species named in the overall stoichiometric equations, they would be bimolecular and termolecular reactions, respectively. There is considerable doubt, though, about whether this actually occurs. 

Taking the mean molar heat capacities of gaseous hydrogen, iodine and hydrogen iodide as 6.95, 8.02 and 7.14 cal. deg. , respectively, calculate the heat of formation of hydrogen iodide from the gaseous elements at 225 C. The heat of sublimation of solid iodine is 58.5 cal. g. at 25 C. 

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