Interaction with iodine

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. 

Since phenol has an appreciable dipole moment, and no low energy acceptor orbitals, it should interact best with the donors that have the largest lone pair dipole moment — the oxygen compounds. Iodine has no dipole moment and the interaction with iodine is expected to be essentially covalent. Iodine should interact best with the donors that have the lowest ionization potential, i.e., the ones whose charge clouds are most easily polarized. Similar considerations have been employed to explain the donor strengths of primary, secondary and tertiary amines 35a) and the acid strengths of (35b) ICl, Bt2, I2. CeHsOH and SO2. 

Amylopectin Amylopectin is similar to amylose except that the glucose chain has branches. These branches involve linkages at the -CH2OH position ( 6), which makes them a 1 —> 6 linkages. Amylopectin is water-soluble it also interacts with iodine to form a reddish-purple complex. Typically, amylopectin is ten times the size of an amylose molecule. Digestion requires (3-amylase (1 4 linkages) and a second... 

Glycogen, animal starch, is similar to amylopectin, but it features more branching and tends to have a higher molecular weight. Glycogen occurs in the liver and muscle tissue. It interacts with iodine to produce a red color. 

Triphenyl-X -phosphorin interacts with iodine or other polarizable electron donors, as well as with such electron acceptors as tetrachloro-p-benzoquinone and tetracyanoethylene, to produce deeply colored solutions. Such coloration points to the formation of charge-transfer complexes (see p. 43). In some cases electron transfer occurs with the formation of 2.4.6-triphenyl-X -phosphorin cation radical and tetracyanoethylene anion radical. Weber is currently investigating the details of these reactions (see p. 43). 

Stereoselective vicinal diamination of dihydropyridines 309 by electrophilic interaction with iodine in the presence of secondary amines leading to tetrahydropyrimidines 312 is described in [338, 339] (Scheme 3.107). The... 

The mechanism of glycal addition was further examined by Horton and coworkers,86 who have used this method to form (7S,9S)-4-demethoxy-7-0-(2,6-dideoxy-2-iodo-a-L-mannopyranosyl)-adriamycinone87 and -daunomycinone,88 which are iodinated analogs of natural antitumor compounds. The nature of the solvent was found to be critical. In particular, they were able to generalize that in non-coordinating polar solvents, where no possibility for interaction with iodine exists—that is, no lone-pair interactions—the formation of the iodonium intermediate was irreversible, and the resultant stereochemistry reflects the electronic... 

Cu(n) forms a 5-coordinate complex with thyroxine which involves axial interaction with iodine at the apex of a square pyramid [12]. (559)... 

Both PPSe and PPTe turn black and undergo weight Increases of 20 and 150%, respectively, on exposure to Iodine, with the conductivity of the PPSe samples being no more than 10 H(ohm-cm) l while the PPTe samples had a conductivity range of 10 -10 ohm-cm)-- -. Electron transfer does not appear to be involved in the interaction of I2 with PPSe and PPTe since the solid state spectra show the maxima of the original polymers with long tails into the near infrared. In the case of PPTe, the interaction with iodine largely involves formation of a tetracoordinate diaryl tellurium diiodide (24). Reduction of this material with sodium sulfide (24) leads to-recovered PPTe, identified by its IR spectrum. 

Charge-transfer (C-T) bands have been located in the spectra of solutions of phenanthridine in 1,2-dimethoxyethane containing bromine solutions containing up to a 2 1 mole ratio of halogen to base were examined, but the structure of the species involved is not clear. Phenanthridine satisfies the conditions necessary for both n and tt- donation and n donation is apparently involved in the charge-transfer interaction with iodine. The equilibrium constant for this reaction has been determined spectrophotometrically, but the claimed correlation (for a series of A -heteroaromatic bases) between values (in 50% ethanol) and these C-T equilibrium constants appears to be an unsatisfactory one and in any case lacks theoretical justification, since it is doubtful whether dissociation constants provide, in general, an accurate measure of w-ionization potentials. In particular, the excellent correlation in the case of phenanthridine is probably fortuitous, since the authors report that w-halogen interactions are markedly sensitive to steric factors which are almost... 

Cyclo-(Gly-Sar) (80), Cyclo-(Sar2) (81) and the analogous linear peptide acetyl sarcosine dimethylamide (AcSarDMA) (81) were dissolved in chloroform and their interactions with iodine were investigated. The complex formed exhibited a new absorption at 480 nm for Cyclo-(Sar2)-l2 and at 363 nm for AcSarDMA-l2. The limited solubility of Cyclo-(Gly-Sar) in chloroform made it difficult to detect new absorption due to complexes with iodine. In either case, on mixing iodine with peptide the absorption due to iodine at 510 nm decreased and a distinct isosbestic point was observed, which enabled us to determine the equilibrium constant K for the complex formation. K values are listed in Table 2. K for AcSarDMA-l2 is greater than K for Cyclo-(Sar2)-l2- Investi tions by infrared spectroscopy showed that the... 

The monitoring program of iodine intake and thyroid diseases (DanThyr) was designed to secure optimal iodine nutrition of the Danish population, and also to improve knowledge on how to evaluate the iodine status of a population. Moreover, the design would give information on the epidemiology of thyroid disorders in areas with different levels of iodine intake, and the effects of an increase in iodine intake. An additional aim was to clarify the role of various environmental factors for the development of thyroid disease in the population, and in particular to study how these factors may interact with iodine intake. 

Amylose and amylopectin are the Isotactlc homo-polymers of oc-D-glucose which interact with iodine (13) in aqueous systems to give the characteristic blue coloured complexes. 

The explanation of this effect can be conceived as follows. Phenol has a fairly high dipole moment and has no low-energy acceptor orbitals, whereas iodine has no dipole moment hence interactions with iodine may be expected to have more covalent character than the analogous reactions with phenol. Accordingly, iodine will react more readily with the better polarizable reaction partners possessing lower ionization potentials. Similar considerations may be employed to interpret, for example, the sequence of basic strengths of primary, secondary and tertiary amines [Dr 63], and the sequence of acid strengths of iodine monochloride, elemental bromine, elemental iodine, phenol and sulphur dioxide [Dr 62]. 

Aminoboranes interact with iodine in inert solvents to yield red-brown solutions 360 to 390 mp) the spectra of solutions containing varying... 

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