Halogen complexes extraction

In chemical shifts in n.m.r. spectra of In-halogen complexes have been measured in solution. They fall in the following sequence InCl < InBr < [In(H20)e] + < Inl. In linewidths are largely determined by quadrupole relaxation, and they may be used to study the symmetry of the complexes. Indium, when extracted into organic solvents from aqueous HCl, HBr, or HI solutions, exists as tetrahedral species, although the existence... 

Pu, Zr(+Nb), and Ce and iTithenlum complexes. Neptunium, plutonium, and cerium are made less extractable by reduction to lower oxidation states. Favorable separation of tiranlum from the other elements may be achieved by control.of the nitric acid and saltlng-out agent concentrations. Free halogens are extracted. These elements may be eliminated from solution prior to uranliim extraction. The halogens also combine chemically with a number of solvents eg,. 

The quaternary ammonium salts (QAS) are widely used as ionofores of ion-selective electrodes and extractants of metals halogenic anion complexes. The influence of the QASes nature with various methyl groups contents on the cadmium extraction from bromide media has been investigated. 

The ability of quaternary ammonium halides to form weakly H-bonded complex ion-pairs with acids is well established, as illustrated by the stability of quaternary ammonium hydrogen difluoride and dihydrogen trifluorides [e.g. 60] and the extractability of halogen acids [61]. It has also been shown that weaker acids, such as hypochlorous acid, carboxylic acids, phenols, alcohols and hydrogen peroxide [61-64] also form complex ion-pairs. Such ion-pairs can often be beneficial in phase-transfer reactions, but the lipophilic nature of H-bonded complex ion-pairs with oxy acids, e.g. [Q+X HOAr] or [Q+X HO.CO.R], inhibits O-alkylation reactions necessitating the maintenance of the aqueous phase at pH > 7.0 with sodium or potassium carbonate to ensure effective formation of ethers or esterification [49,64]. 

One can set up to do this using the competition between dimerization and halogen atom abstraction from RX to form the rhodium(III) halide complex. As a function of [RX], the product ratio is quite easily evaluated. From that, one can get the rate constant ratio but, knowing independently the rate constant for dimerization, it is possible to extract from those data rate constants for reactions of the rhodium(II) complex with these organic halides. The rate constants obtained are listed in Table I. 

The major drawback of phenyl derivatives of BNOPCs is that they are only scarcely soluble in classical hydrocarbon diluents without the addition of massive amounts of phase modifiers, such as TBP or TOPO. They are, however, soluble in halogenated and nitro-halogenated organic diluents (130). Furthermore, the anomalous aryl strengthening effect also increases the extraction of other fission products, such as Zr, Mo, Tc, and Fe, which can only be avoided by introducing specific hydrophilic complexants (e.g., acetohydroxamic acid). 

HF amine complexes are also employed for nucleophilic displacement of halogens and hydroxyls. Olah and coworkers used the reaction with and without the help of NCVBF for preparing fluoroadamantanes and fluorodiadamantanes28. They also found that an electrophilic salt would extract an hydride a to a C—Br moiety, followed by F attack on the resulting carbocation to form vicinal fluorobromo alkanes (equation 15)29. 

Formation of complexes with ratio M L = 1 3 is observed for the 8-hydroxyquinoline and its derivatives [44]. Americium and plutonium solid compounds were obtained in the form of complexes [Am(Ox)3], [Pu(Ox)3], [Am(DCOx)3], [Am(MCOx)3]. Chelates with halogenated 8-hydroxyquinoline are better extractable from the solution than complexes with 8-hydroxyquinoline. Plutonium (111) easily oxidizes in the presence of 8-... 

Manoli and Samara, 1999) or capillary electrophoresis (Martinez et al., 1999). All these methods require sophisticated and expensive instruments which are difficult to transport and to adapt for on-site operation or for field monitoring. Moreover, these methods normally include an extraction step (liquid-liquid or solid phase extraction) for which a complex calibration process is needed to account for the appreciable loss of analyte (Thurman and Mills, 1998 Simpson, 2000) that occurs during the process. Further, they involve the use of organic solvents including halogenated compounds on whose use there are legal limitations (US EPA, 1998). 

In the first part of the reaction (Scheme 13), the catalytic complex will extract the halogen atom from the initiator (R-X) by a redox process. Then a radical is created that will propagate to the monomer. The growing chain will fix a halogen atom produced by the catalytic complex to form a dormant species. The chain will be reactivated when the catalytic complex traps the chain-end halogen atom to be oxidized. The chain is then able to propagate (Scheme 13). Some termination and transfer reactions occur but remain minor. 

Ihe "induced hexagonal structure is stable caily in the presence of the included oomapound. Removal of the included partner by extraction or volatilization causes a rapid breaMown of the urea lattice. Aliphatic hydrocarbons, alcohols, ketones, esters, ethers, amines, nitriles, mono- and dicarboj lic acids, and their halogen derivatives can be included in the urea complex. 

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