Fluorides hydrolytic reactions

Stein, L., Hydrolytic Reactions of Radon Fluorides, Inorg. Chem. 23 3670 (1984). 

Considerable data have been assembled concerning the physical and chemical properties of the nitrogen fluorides (6), yet a review of the literature revealed no systematic study of die reactions of these compounds with water. Although some isolated experiments relating to the hydrolysis of these gases have been reported (6), the results have not been critically analyzed. Usually these hydrolytic reactions were reported as observations noted during the investigation of other properties. 

The compounds of the III, IV and VI oxidation states are the ones with which the radiochemist deals, and the insoluble compotinds are of primary interest. Of these the insoluble hydroxides, fluorides, and oxalates, phosphates and peroxides of the m and IV states are of major interest in precipitation and co-precipitation reactions and are described in more detail in that section. One of the great complicating factors in Pu chemistry is the formation of a polymeric form by hydrolysis in dilute acid or neutral solutions. The polymeric form can be quite intractable in many reactions, and may be difficult to destroy. The section on hydrolytic reactions of Pu gives details. 

The above-considered calculational data point to high effectiveness of the bifunctional catalysis in hydrolytic reactions and the reactions related to these, due to involvement of molecular chains of water and ammonia, as well as to the preferability in these reactions of a concerted mechanism. This conclusion is fairly general and is corroborated by calculations on other types of nucleophilic reactions, such as hydrolysis of methyl fluoride, tautomerization of pyridine in aqueous solution etc. [110]. An advisable piece of work would apparently, be an analysis, in the light of the conclusions discussed, of mechanisms of the catalytic act in enzymic hydrolysis reactions of the ester and peptide bonds. In the most advanced up-to-date models for, e.g., the reactions with participation of a-chymotrypsin (see Ref. [Ill]), the steps of the base and the acid catalysis are separated. The latter is commonly thought [84, 111] to be operative at the stage of enzymic decomposition of the tetrahedral intermediate. However, taking into account the possibility of realization of the conformationally excited states of the active enzymic center, it would not be hard to think of some realistic schemes of concerted mechanisms, the more so that the fast growing body of calculational material continuously supplies fresh evidence in favor of such mechanisms. 

Fluorides of the actinyl ions are very soluble in water, as are the heavier halides of all oxidation states of the actinides. For these, however, hydrolytic reactions... 

There are some reports in the literature concerning the cleavage of bonds between silicon and an sp2-hybridized carbon in silylcyclopentadienyl compounds of type 4 (Section II.B). For example, equation 4697 shows hydrolytic fission in the reaction of a tris(trimethylsilyl) substituted ferrocene derivative with aqueous tetrabutylammonium fluoride. 

A variety of polymers contain the element boron.42,44,52 60 One of the simplest consists of chains of boron fluoride, of repeat unit -BF-, and can be prepared by the reaction of elemental boron with boron trifluoride at high temperatures. The polymer is a rubbery elastomer, but it has been little studied because of its hydrolytic instability and tendency to ignite spontaneously in air.42 However, a variety of other structures are formed with a number of metals, for example chains with Fe, ladders with Ta, sheets with Ti, tetragonal structures with U, and cubic structures with Ca and Ar. Boron also forms chains that are analogues of poly(dimethylsiloxane), with repeat unit -BCH-O-42... 

From the above it can be seen that the hydrolytic behavior of N2F2 is quite different from those of the other binary nitrogen fluorides discussed earlier. Difluorodiazine is strongly endothermic (12) and thermodynamically unstable (11) this makes it necessary to consider not only direct chemical attack by water but also the thermal decomposition to the elements. The reactivity of d -N2F2 toward glass (2) presents an additional question of possible competing reactions with the container walls. 

Trialkylsilyl protection of carboxylic acids and amines is rare owing to hydrolytic lability. Nevertheless, synthetically useful silicon protecting groups have been developed for these functional groups in which the requisite stability is achieved by incorporating the silicon atom into a 2-(trimethylsilyl)ethyl substituent. The principle is illustrated [Scheme 1.9] by the reaction of 2-(trimethylsilyl)ethyl esters with tetrabutylammonium fluoride the pentavalent siliconate intermediate fragments with loss of ethylene and fluorotrimethylsilane14-15 to liberate a carboxylic arid as its tetrabutylammonium salt. 

The fact that stronger bases speed up both the coupling and the hydrolytic deboronation means that the choice of base is not always obvious. Although aqueous carbonate is the one most commonly used, stronger alkoxide bases appear to yield the best results for stericaUy hindered boronic acids. For base-sensitive substrates, bicarbonate can be used successfully when THF is the organic cosolvent. However, this base is less successful when employed with mostly nonaqueous reaction conditions. On the other hand, fluoride, an even weaker base, appears to work well with both aqueous and nonaqueous protocols. ... 

The iodine atom in PhIF4 can act as a fluoride ion acceptor in the reaction with 1,1,33,5,5-hexamethylpiperidinium fluoride (pip+F ) as a source of nearly naked fluoride ions. PhIF4 reacts with pip+F in acetonitrile at -30 °C to form the colorless, hydrolytically sensitive adduct pip+CeHsIFs", which has been characterized by Raman and NMR spectroscopy and its single X-ray crystal structure [716],... 

Nearly all trifluoromethyl arsenicals are hydrolyzed quantitatively by base affording fluoroform. This reaction has been of value in the analysis of these compounds. Exceptions are the compounds (CF3)2AsH, CF3ASH2, and (CF3)2As— As(CF3)2 which give fluoride and carbonate as well as fluoroform. Hydrolysis of the diarsine is believed to involve hydrolytic fission of the As— As bond (30). 

In the case of cysteine (5) the product obtained is contaminated by cystine and also by thiazolidine carboxylic acid (obtained by reaction of cysteine and formaldehyde, the latter arising from hydrolytic decomposition of acetamidomethanol, see section VI). However, the product could easily be purified by using ion exchange columns. On the other hand, anhydrous conditions should avoid the decomposition of the acetamidomethanol and indeed a reaction using hydrogen fluoride as a solvent results in quantitative yield of the pure product". 

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