115-25-3 Perfluorocyclobutane

Health and Safety Factors. Completely fluorinated alkanes are essentially nontoxic (16). Rats exposed for four hours to 80% perfluorocyclobutane and 20% oxygen showed only slight effects on respiration, but no pathological changes in organs. However, some fluorochemicals, especially functionalized derivatives and fluoroolefins, can be lethal. Monofluoroacetic acid and perfluoroisobutylene [382-21-8] are notoriously toxic (16). 

Uses. The chemical inertness, thermal stability, low toxicity, and nonflammability of PFCs coupled with their unusual physical properties suggest many useflil applications. However, the high cost of raw materials and manufacture has limited commercial production to a few, small-volume products. Carbon tetrafluoride and hexafluoroethane are used for plasma, ion-beam, or sputter etching of semiconductor devices (17) (see loN implantation). Hexafluoroethane and octafluoropropane have some applications as dielectric gases, and perfluorocyclobutane is used in minor amounts as a dielectric fluid. Perfluoro-1,3-dimethyl cyclohexane is used as an inert, immersion coolant for electronic equipment, and perfluoro-2-methyldecatin is used for... 

A large number of by-products are formed in this process, mostly in trace amounts more significant quantities are obtained of hexafluoropropylene, perfluorocyclobutane, l-chloro-l,l,2,2-tetrafluoroethane, and 2-chloro-l,l,l,2,3,3-hexafluoropropane. Small amounts of highly toxic perfluoroisobutylene, CF2=C(CF2)2, are formed by the pyrolysis of chlorodifluoromethane. 

RO—CF=CF2, are obtained by reaction with sodium salts of alcohols (26). An osone—TFE reaction is accompanied by chemiluminescence (27). Dimerization at 600°C gives perfluorocyclobutane, C Fg further heating gives hexafluoropropylene, CF2=CFCF2, and eventually perfluoroisobutylene, CF2=C(CF2)2 (28). Purity is deterrnined by both gas—Hquid and gas—soHd chromatography the in spectmm is complex and therefore of no value. 

It has been reported that perfluoroisobutylene and perfluorocyclobutene undergo 1,2 cycloaddition with l-(N-morpholino)isobutylene in ether at room temperature to give the corresponding perfluorocyclobutane derivatives ]20a). Enamines of cyclic ketones produce only simple alkylation products when treated with these perfluoroolefins. 

Trichlorofluoromethane o ,a ,a -Trifluorotoluene Trifluoroacetic acid Carbon tetrafluoride Fluorobenzene Perfluorocyclobutane... 

Figure 3.3. Synthesis of trifluorovinyl ether monomers and perfluorocyclobutane aromatic ether polymers.

A variety of polymer compositions that use this type of polymerization chemistry can be envisioned. In addition to the polyarylate homopolymers that have been described in this chapter, random or block copolymers can be prepared with reasonable ease by the combination of different monomers or oligomers. These compositions can be designed to optimize thermal, mechanical, dielectric, or optical properties of a polymer system. Also, the trifluorovinyl ether functionality can be incorporated into other high-performance polymer systems with relative ease.34,35 The perfluorocyclobutane polyarylate chemistry is a versatile approach to the preparation of high-performance polymers, which is just beginning to demonstrate its utility. 

The monomers for the perfluorocyclobutane polyarylates were prepared in two steps from phenolic starting materials. 

Smith, D. W., Jr. Ji, J. Narayan-Sarathy, S. Neilson, R. H. Babb, D. A. Fluorosilicones Containing the Perfluorocyclobutane Aromatic Ether Linkage. In Silicones and Silicone-Modified Materials-, Clarson, S. J., Fitzgerald, J. J., Owen, M. J., Smith, S. D., Eds. ACS Symposium Series 729 American Chemical Society Washington, DC, 2000 pp 308-321. 

Trifluorostyrene-based monomers and fheir derivatives are known to exhibit dimerization preferentially over polymerization in confrasf to fhe hydrocarbon analogue slyrene. Eord, DesMarfeau, and Smifh, Smifh and Babb,i i and Smith et al. have advantageously used this behavior to produce 6 (where E can be a large number of differenf spacer groups buf also typically be sulfonamide-based) via cyclopolymerization of multifunctional monomers bearing at least two trifluorovinyl ether units. The polymers themselves have perfluorocyclobutane (PFCB) rings as part of the main chain. 

Smith, D. W., Jr. and Babb, D. A. 1996. Perfluorocyclobutane aromatic polyethers. Synthesis and characterization of new siloxane-containing fluoropolymers. Macromolecules 29 852-860. 

Rigid gas-permeable polymers containing perfluorocyclobutane substituents, (IV), were prepared by Schorzman et al. (4) and used in contact or intraocular lenses. 

Tris(diethyl)amino]phosphoniuni 2,2,3,3,4,4-hexafluorocyclobutane ylide (2) is a very hydroscopic solid, which is stable for long periods of time when stored under anhydrous conditions.13 It is unreactive towards most functional groups such as C = C bonds, ketones, aldehydes, and esters but reacts smoothly under neutral conditions with alcohols or carboxylic acids with replacement of the hydroxy group by a fluorine atom.44,45 Other tris(dialkylammo-nium)phosphonium perfluorocyclobutanes have been synthesized however, they are less reactive fluorinating reagents.44,45... 

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