Iodine molecules

Figure Al.6.20. (Left) Level scheme and nomenclature used in (a) single time-delay CARS, (b) Two-time delay CARS ((TD) CARS). The wavepacket is excited by cOp, then transferred back to the ground state by with Raman shift oij. Its evolution is then monitored by tOp (after [44])- (Right) Relevant potential energy surfaces for the iodine molecule. The creation of the wavepacket in the excited state is done by oip. The transfer to the final state is shown by the dashed arrows according to the state one wants to populate (after [44]).

Steinfeld J I and Klemperer W 1965 Energy-transfer processes in monochromatically excited iodine molecules. I. Experimental resulted. Chem. Phys. 42 3475-97... 

Iodide and iodate ions react under the influence of protons to yield iodine molecules which react with amylose to yield a blue clathrate complex ... 

Each time a molecule of H collides with an iodine molecule, reaction may occur. The frequency of these encounters, for a particular Ha molecule, is determined by how many I molecules are present. Doubling the number of 1 molecules per unit volume would just double the collisions. Tripling the number of I molecules per unit volume would triple the collisions. Since the iodine partial pressure fixes the iodine concentration, the rate of the reaction is proportional to the iodine partial pressure ... 

In the same way, a particular iodine molecule must find a hydrogen molecule to react. The rate of the reaction is proportional to the partial pressure of the hydrogen ... 

Among the molecules, however, business is going on as usual. Iodine dissolves by the detachment of surface layer molecules from the iodine crystals. The rate at which this process occurs is fixed by the stability of the crystal (tending to hold the molecules in the surface layer) and the temperature (the thermal agitation tending to dislodge the molecules from their lattice positions). As the dissolving continues, the concentration of iodine molecules in the solution increases. 

The simple form of the equilibrium expression (4) follows directly from the dynamic nature of the solubility equilibrium. There must be a dynamic balance between the rate that iodine molecules leave the ciystal and the rate that iodine molecules return to the crystal. To understand this dynamic balance, we must consider the factors that determine these two rates. 

Experiment shows that heat is absorbed as iodine dissolves. The regular, ideally packed iodine crystal gives an iodine molecule a lower potential energy than does the random and loosely packed solvent environment. We see that the second factor, tendency toward minimum energy, favors precipitation and growth of the crystal. 

Ideal localized adsorption, 5, 10 Infrared method, 373, 374 Initiators of polymerization, 148 Intramolecular London energies, 74, 78 Iodine molecule intramolecular London energy, 78... 

Reaction of iodine with Pt(phen)Cl2 gives compounds with the unusual stoichiometries Pt(phen)I (a = 5,6) these contain Pt(phen)I4 molecules and free iodine molecules in the lattice. Pt(bipy)I4 has also been made [172], Macrocyclic complexes of platinum(IV) are readily made by oxidation ... 

On the basis of all these results and his own investigations on chloro- and bromo-de-diazoniations (Galli, 1981), Galli proposed in 1988 that iodo-de-diazoniation, after formation of the aryl radical in the initiation reaction (Scheme 10-22) follows three coupled iodination chain reactions based on the formation of the I2 molecule and the If anion in the step shown in Scheme 10-23, namely iodine atom (I ) addition (Scheme 10-24), and iodine abstraction from I2 and If in Schemes 10-25 and 10-26 respectively. Aryl radicals and iodine molecules are regenerated as indicated in Scheme 10-27. The addition of iodide ion to aryl radicals forming the radical anion [Arl] -, as in Scheme 10-28, is considered an unlikely pathway, as that reaction has been found to be reversible (Lawless and Hawley, 1969 Andrieux et al. 1979). 

Detection by iodine is usually based on physical concentration of iodine molecules in the lipophilic chromatogram zones without any reaction occurring. Iodine is more strongly enriched in the substance zones than in the neighboring polar, substance-free silica gel or alumina layer. The result is brown chromatogram zones on a yellow background [3]. 

In addition to the iodine staining resulting from adsorption or purely physical solution of the iodine molecules in the lipophilic chromatogram zones, many substances can also be made visible by chemical reaction with the iodine [9]. In such... 

Charge transfer complexes can also be formed, as shown using a tertiary nitrogen compound as an example. An iodine molecule flrst adds to the nitrogen compound ... 

The complex that is formed can dissociate to form a cation (n-tr-complex) and an iodide anion, with the iodide ion reacting with the excess iodine molecules that are present. In addition the decomposition of the n-cr-complex can lead to the formation of highly reactive iodine cations, which can initiate further reactions — e.g. oxidations or electrophilic substitutions of aromatic systems [11, 13]. 

A dilute I2/CCI4 solution was pumped by a 520 nm visible laser pulse, promoting the iodine molecule from its ground electronic state X to the excited states A,A, B, and ti (Fig. 4). The laser-excited I2 dissociates rapidly into an unstable intermediate (I2). The latter decomposes, and the two iodine atoms recombine either geminately (a) or nongeminately (b) ... 

E. Rabinowitch and W. C. Wood, Properties of illuminated iodine solutions. 1. Photochemical dissociation of iodine molecules in solution. Trans. Faraday Soc. 32, 547-555 (1936). 

Hartfield, R.J., Interpretation of spectroscopic data from the iodine molecule using a genetic algorithm, Appl. Math. Comp., 177,597,2006. 

The absorption in the visible region is assigned to the HOMO-LUMO transition of adsorbed iodine molecules. This band is shifted from the value of 540 nm, typical of iodine in gas-phase, to 490 nm, because of the interaction with the pore walls. 

Iodine molecules adsorbed onto the structural aromatic rings provide information on the electron-donor strength, which appears to be higher in phenylene-bridged PMO than that reported for benzene and comparable with that reported for p-xilene. Traces of I3" species were also detected. From a comparison between two phenylene-bridged PMOs with different degree of order in the walls, aromatic rings in the material with amorphous walls appear more available for interaction with iodine. 

In consideration of the clinical importance of being able to visualize any implant material within the body, radio-opaque hydrogels for NPR have been formulated [69]. Copolymers of iodobenzoyl-oxo-ethyl methacrylate (4IEMA) and hydrophilic PVP or hydroxylethyl methacrylate (HEMA) exhibit appropriate swelling characteristics, viscoelastic mechanical properties, and excellent cytocompatibility [69]. Moreover, inclusion of the covalently attached iodine molecules allowed for hydrogel visualization via X-ray in a porcine cadaveric spine model [69],... 

The decrease in amount of bound iodine with increase in iodide-ion concentration is reflected in a decrease in the wave length of maximum absorption of the complex.166 On the basis of Kuhn s theory for polyenes,171 this has been related to the breaking of resonating chains of iodine molecules.172... 

Gilbert and Hybart,189 from the results of potentiometric titrations, have suggested that iodine is bound as a complex of one or two iodine molecules together with none, one, or two iodide ions, depending on the concentration of iodide present. 

The local environment of 1 in this system is structurally reminiscent of some I7 ions that feature a central 1 interacting with three di-iodine molecules with an approximate local C3v symmetry.16... 

A different structural motif is observed in the compound with the stoichiometry (tu)3(I2)5 (tu = thiourea) which according to the authors, consists of a tu-I2 spoke -like strong C.-T. adduct, a (tu)2(I3) + cation counter-balanced by an I3, and a perturbed di-iodine molecule.17 The strong tu-I2 adduct and the V -shaped planar tu-I I- I-tu + cation are bridged at their terminal an central iodide atoms, respectively, by a di-iodine molecule (Figure 9). 

A polymeric structure is also observed in the adduct LE 2I2 (LE = 4,5-6z s(bromomethyl)l,3-dithiole-2-thione). LE-I2- I2 bent-shaped units, which are typical in discrete extended spoke adducts with 1 2 (LE/I2) stoichiometry, are joined head-to-tail by soft-soft I- -I interactions involving the terminal iodide atom of the LE-I2 moiety and the terminal iodide atom of the second coordinated di-iodine molecule.37... 

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