Alkanes perfluorinated

Perfluorinated alkanes and cycloalkanes are prepared from the corresponding hydrocarbons, either by electrochemical fluorination or by cobalt trifluoride fluo-rination [3], Many perfluorinated solvents are available commercially covering a wide selection of boiling points and densities. Some examples of perfluorinated solvents are listed in Table 3.1 together with their key physical properties. 

Another approach to isolate the catalyst from the products is the application of perfluorinated catalytic systems, dissolved in fluorinated media [63], which are not non-miscible with the products and some commonly used solvents for catalysis like THE or toluene at ambient temperature. Typical fluorinated media include perfluorinated alkanes, trialkylamines and dialkylethers. These systems are able to switch their solubility properties for organic and organometallic compounds based on changes of the solvation ability of the solvent by moving to higher temperatures. This behavior is similar to the above-mentioned thermomorphic multiphasic PEG-modified systems [65-67]. 

Type II (slow homodimerization) Styrene, allylstannanes" Styrene, 2° allylic alcohols, vinyl dioxolanes, vinyl boronates Styrenes (large ortho substit.) " " 2° allylic alcohols, vinyl epoxides, unprotected 3° allylic alcohols, acrylates, acrylamides, acrylic acid, acrolein, vinyl ketones, vinyl boronates perfluorinated alkane olefins ... 

Type IV (spectators to CM) 1,1-Disubstituted olefms " 1,1-Disubstituted olefms, disub. o ,/ -unsaturated carbonyls, 4° allylic carbon-containing olefins, perfluorinated alkane olefins, 3° allylamines (protected)" Vinyl nitro olefins, protected trisubstituted allyl alcohols, a,/ -olefin of 2-subst. 1.3- butadienes, a,/ -olefm of electronically deactivated 1.3- butadienes ... 

Perfluorinated alkanes and a number of hydrogen-containing fluorinated alkanes can, in general, be considered as being biologically inert materials, unless hydrogen fluoride or fluoride ion elimination in vivo is extremely facile (Table4). 

It is important to use dry air and dry equipment because difluorotris(perfluoroalkyl)-25-phos-phanes react very rapidly with water to form tris(perfluoroalkyl)phosphane oxides. Under these conditions, the electrochemical perfiuorination of triethyl-, tripropyl-, and tributylphosphanc oxides yields 15-50% of the corresponding difluorotris(perfluoroalkyl)-A5-phosphanes. A decrease in yield is observed with a longer carbon chain (chain with 2C atoms 42%, with 6C atoms 24 %).63 Byproducts are perfluorinated alkanes. Addition of bromine makes it possible to electrochemically fluorinate trialkylphosphane oxides with a carbon chain length of C5 to... 

Highly fluorinated or perfluorinated alkanes are rather difficult to hydrogenolyze therefore, more efficient reagents are used. It is noteworthy that trifiuoroiodomelhanc reacts with lithium aluminum hydride according to the equation 12... 

As well as atmospheric sources, pyrolysis of fluorine-containing polymers, which may occur in engine oil additives, non-stick cookware or incinerated medical equipment (i.e. syringes) and household waste, may also produce TFA. This process may also produce perfluorinated alkanes and cycloalkanes, which have significant GWP, and have estimated tropospheric half-lives of more than 2000 years. Trifluoroacetate may also be produced by metabolism of trifluoromethyl-containing drugs such as Prozac, and anaesthetics including halothane and iso-fluorane [4],... 

Using 2-chloro-2,4,4,-trimethylpentane as the initiator and ethylaluminum dichloride as the Lewis acid, McDonald [5] and Shaffer [6] prepared high molecular weight polyisobutylene with perfluorinated alkanes as polymerization solvents. 

Perfluorinated alkanes, alkenes or cycloalkanes show a high thermal stability, heating to temperatures over 1000 C results in radical cleavage to give short chains or alkenes.However, C C bonds which contain quaternary and tertiary carbons are cleaved at lower temperatures than those between secondary carbons. In the presence of bromine, chlorine or toluene, cleav age products are isolated, e.g.Rp—Rp - 2 RpBr Other examples involve pyrolyses. ... 

Although known for many years, perfluorinated alkanes and ethers are becoming widely used as solvents for biphasic catalysis. They have not been employed as solvents for the synthesis of coordination compounds although metal complexes dissolve in them when suitable modifications are made to the ligands (see Chapter 1.38). 

Passage of 2-heptafluoropropylcyclohexan-l-one saturated with Ij through a carbon arc gave COFj, along with a mixture of Cj and C3 perfluorinated alkanes [623]. 

As an analog to the term aqueous, the term fluorous was introduced to highlight the fact that one of the phases of a biphasic system is richer in fluorocarbons than the other [34]. Perfluorinated alkanes, dialkyl ethers, and trialkylamines have unusual... 

Perfluorinated alkanes, dialkyl ethers, and trialkylamines are unusual because of their nonpolar nature and low intermolecular forces. Their miscibility, even with common organic solvents such as toluene, THF, acetone, and alcohols, is low at room temperature, so these materials could form fluorous biphase systems [2]. The term fluorous was introduced [4, 5], as the analog to the term aqueous, to emphasize the fact that one of the phases of a biphase system is richer in fluorocarbons than the other. Fluorous biphase systems can be used in stoichiometric... 

The most effective fluorous solvents are perfluorinated alkanes, perfluorinated dialkyl ethers, and perfluorinated trialkyl amines. Their remarkable chemical inertness, thermal stability, and nonflammability coupled with their unusual physical properties make them particularly attractive for catalyst immobilization. Furthermore, these materials are practically nontoxic by oral ingestion, inhalation, or intraperito-neal injection [7]. Although their thermal degradation can produce toxic decomposition products, such decomposition generally begins only at very high temperatures well above the thermal stability limits of most organometallic compounds. 

Another possibility is a suspension polymerization in media other than water. For example, a suspension polymerization using a liquid perfluorinated alkane as the dispersing phase was reported [119]. In other cases, a two-step swelling and polymerization method was applied to prepare molecularly imprinted beads [120]. 

The characteristic of fluorous phase operation is (like using supercritical carbon dioxide see Chapter 6) that the catalysts have to be made fluorous-soluble by incorporating fluorocarbon moieties in their structure in appropripate size and number (Figure 10). The most effective fluorocarbon moieties are linear or branched perfluoralkyl chains with high carbon numbers that may contain other heteroatoms (the fluorous ponytails ). The best fluorous solvents are perfluorinated alkanes, perfluorinated dialkyl ethers, and perfluorinated trialkylamines [28, 39). 

Carrier liquid and segment liquid consist normally of substances or mixtures with very different electrical properties. For example, the dielectric constants of an oil or a perfluorinated alkane (typical carrier liquids for aqueous segments) are much smaller than those of water. Electrical measurements can use differences in specific resistances of direct or alternating cm-rent. In principle, changes in electrochemical properties like media-dependent electrode potentials or Faraday currents can also be used for the detection of the interfaces. 

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