Iodine complex solvent effects

When pyridinium hydrochloride was treated at 250°C with iodine monochloride in the presence of aluminium chloride, a 2-pyridylpyridinium salt was formed. Both 1 1 and 1 2 complexes formed when iodine monochloride or iodine reacted with pyridine (80AJC1743). Formation constants for the charge-transfer complexes between iodine and pyridine (and pico-lines) have been measured [84JCS(P2)731], and solvent effects on the... 

The electron donor-acceptor molecular complexes between iodine and thiazole, benzothiazole, and some derivatives have been studied in several organic solvents by UV spectroscopy <87CJC468>. In all cases, the presence of the thiazole ring produces a displacement of the Amax iodine band at 512 nm towards shorter wavelengths and a decrease of its absorbance. Moreover, a sharp isosbestic point near 470 nm was observed for all iodine-thiazole complexes. 2-Aryl and 2-hetarylbenzothiazoles showed fluorescence, the maxima of emission being between 350 nm and 395 nm. Both substituent and solvent effects on the spectra were observed <93MI 306-02>. The photophysical properties of bis(benzothiazolylidene)squaraine dyes have also been studied <93JPC13625>. 

In a recent application of DFT to experimentally noted solvent effects on the C shifts in iodoalkynes, it was found that charge transfer complexes from DMSO solvent molecules to the iodine substituent enhanced for the Cl carbon atom [109]. Nevertheless, the overall solvent effects were found to be deshielding, due to changes in ct . Further application of the same method allowed the identification of the first iodo-substituted cumulene in different solvents [110]. 

By the reaction of iodine and small amounts of liquid ammonia at -75° a black brown solid is formed. A tensimetric deammonation shows that this solid is an addition compound of iodine and ammonia with 2 moles of ammonia per mole of iodine. Further deammonation effects formation of a compound Ij.NH finally, I remains. Ammonolysis of iodine takes place only to a small extent. These brown addition compounds of iodine correspond to the well known brown addition compounds of iodine and ether, alcohol, pyridine or liquid hydrogen sulfide respectively and are looked upon as charge-transfer complexes with iodine as electron acceptor and the solvents as electron donors. This view was proved by the measurement of the charge transfer band of iodine-ammonia in heptane at 229 m i (2). 

Condensation of carboxylic acids with amines in pyridine in the presence of a phosphorous(III) acid/iodine complex is an effective method for the synthesis of amides (eq 5) Pyridine acts as a base and a solvent in this reaction. 

Bhowrmk, B.B. (1971) Solvent effect on the charge transfer intensity of benzene-iodine complex. Spectrochim. Acta, Part A, 27 A, 321—327. 

Safin, D.K., Chmutova, G.A. and Solomonov, B.N. (1985) Solvation effects in complex formation. I. Solvent effect on complexation of seleno- and thioanisole with iodine. Zh. Org. Khim., 21, 1871-1880. 

Dorval-Burnotte, C. and Zeegers-Huyskens, T. (1975) Solvent effect on the stability and charge transfer of the V,V-dimethylacetamide-iodine complex. Ann. Soc. Sci. Brux., Ser. 1, 89, 559-566. 

MoeUendal, H., Grundnes, J. and Augdahl, E. (1969) Solvent effects on strong charge transfer complexes. 11. AA -Dimethylthioformamide and iodine in nonpolar and polar solvents. Acta Chem. Scand., 23, 3525-3533. 

Among the most important indirect methods of analysis which employ redox reactions are the bromination procedures for the determination of aromatic amines, phenols, and other compounds which undergo stoichiometric bromine substitution or addition. Bromine may be liberated quantitatively by the acidification of a bromate-bromide solution mixed with the sample. The excess, unreacted bromine can then be determined by reaction with iodide ions to liberate iodine, followed by titration of the iodine with sodium thiosulphate. An interesting extension of the bromination method employs 8-hydroxyquinoline (oxine) to effect a separation of a metal by solvent extraction or precipitation. The metal-oxine complex can then be determined by bromine substitution. 

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