Positive halogen cryptates

Goaller, R. Le; Handel, Henri; Labbé, Pierre; Pierre, J.-L.

doi:10.1021/ja00318a023

Cited by 16 publications

(5 citation statements)

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“…The differences between the dibromobromates with large cations, especially in dichloroethane, are much less but they exceed the measurement error. These results are not in accord with the common hypothesis of a negligibly small effect of the cation on the reversible dissociation of the dibromobromate anion [19,23,26,27]. This hypothesis was probably formulated on the basis of the results of early measurements in solvents, which stabilize the dibromobromate anion such as acetonitrile [13,24] and measurements in solvents with extensive electrolytic dissociation of salts into a cation and anion such as water and mixtures of water and organic solvents [7,20].…”

Section: Resultsmentioning

confidence: 72%

“…This ion pair is strongly basic under these conditions. No changes over time were noted in the spectra of dibromobromates in chloroform were noted in measurements in an excess of bromide anion [26] or molecular bromine [27]. By the way, Bianchini and Chiappe [27] stress that they maintained the solutions of bromine and tetrabutylammonium bromide for not more than an hour and the results were discarded when the optical density deviated from the expected results.…”

Section: Resultsmentioning

confidence: 96%

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Reversible dissociation of dibromobromates in organic solvents

et al. 2008

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A study was carried out on the reversible decomposition of dibromobromate anions in organic solvents and we found the equilibrium constants for the processes responsible for the distribution of active halogen and hydrogen halide between their different forms in solution. The capacity of the solvent to form hydrogen bonds with the bromide anion, the feasibility of forming a molecular complex with bromine, and the structure of the cation (in solutions with low ionizing capacity) were all found to affect the reversible decomposition of the dibromobromate anion.Organic salts with the dibromobromate anion, Br 3 − , have a set of unique properties, which open the way for their use in a very broad variety of applications [1]. The vapor pressure of bromine above solid crystalline dibromobromates is very low. Many of these salts are suitable for prolonged storage and safe for handling. Numerous studies have shown that the applicability of dibromobromates as electrolyte components for chemical power sources and materials for water purification, brominating agents differing from elemental bromine in their reaction mechanism [2, 3]. The profound differences in the reaction mechanisms of dibromobromates and bromine are seen in differing kinetic behavior, smaller reactivity and greater selectivity in the dibromobromate reactions [4][5][6]. However, there is a special feature in the behavior of dibromobromate solutions, which can cancel out all their advantages relative to molecular bromine. These complexes are capable of reversible dissociation in solution to give bromide anion and molecular bromine [1]. The state of these complexes has been studied in greatest detail for aqueous solution [1, 7-9]. There have been fewer measurements for solutions in organic solvents. Such measurements have far from always been the major concern in these studies. This perhaps accounts for the circumstance that determinations of equilibrium constants and even extinction coefficients do not always agree with one another. The formation of dibromobromates from bromide anion and bromine molecules may reliably be considered to be an exothermal [9], rapid [10] and equilibrium [1] reaction. The equilibrium constants vary in a very broad range depending on the solvent [11]. We can clearly imagine that the concentration of molecular bromine in the case of considerable dissociation of the dibromobromate anion becomes sufficient so that the contribution of the reaction involving bromine, which is much more reactive in many bromination reactions [3][4][5], becomes predominant. The advantages of using dibromobromates in this case would be eliminated. Hence, knowledge of the state of dibromobromate anions in solution is important for the application of these salts. We previously proposed bis(N,N-dimethylacetamide) hydrogen dibromobromate for use as an efficient brominating agent and component in compositions for the decomposition of toxic pollutants [12]. Not only the anion but also the cation is complex in this compound, which introduces additional complexit...

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Section: Resultsmentioning

confidence: 72%

Section: Resultsmentioning

confidence: 96%

Reversible dissociation of dibromobromates in organic solvents

et al. 2008

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“…It has been suggested that depending on the mole ratio an inclusion complex of the type [1.I + ]I À or [1.I + ]I 3 À is possible, and the UV-vis spectra associated with every chemical specie have been characterized. [14][15][16][17] The UV-vis spectrum of a freshly prepared I 2 /I À solution exhibits three absorbance maxima at 353, 287 and 230 nm (see ESI †) which upon addition of a 50 ppm solution of 1 did not present obvious changes due to the formation of a new chemical specie, moreover the resulting spectrum presented a general saturation in different wavelengths even aer several dilutions.…”

Section: Resultsmentioning

confidence: 99%

A rapid and simple colorimetric test for 2,2,2-cryptand (Kryptofix 2.2.2.) in solution

2013

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“…En l'absence de complexant, l'obtention du nitrate d'iode par addition d'une quantitC stoechiomitrique d'iode a du nitrate 1 Bien qu'il n'ait pas Ct C fait d'Ctude fondamentale correspondante, nos rCsultats montrent qu'il doit en &tre de m&me lorsque l'on utilise le Kryptofix 5 ou le diamino-1,6 hexane.…”

Section: Rkactions En L'absence De Complexantunclassified

Influence de la complexation sur la réactivité de nitrates d'halogènes

Gaude¹,

Gellon²,

Goaller³

et al. 1989

Can. J. Chem.

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Iodine nitrate or bromine nitrate in acetonitrile or in chloroform react with a variety of phenolic substrates to form both halogenated and nitrated products. In the presence of strong complexing agents of halonium ions, no reaction occurs, while in the presence of pyridine or triethylamine, only halogenated phenols exhibiting a strong ortho-directing effect of the phenolic function are produced. Keywords: phenols, iodine nitrate, bromine nitrate, halogenation, nitration.

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Positive halogen cryptates

Cited by 16 publications

References 0 publications

Reversible dissociation of dibromobromates in organic solvents

Reversible dissociation of dibromobromates in organic solvents

A rapid and simple colorimetric test for 2,2,2-cryptand (Kryptofix 2.2.2.) in solution

Influence de la complexation sur la réactivité de nitrates d'halogènes

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