Hydrofluorocarbon solvents

This paper is intended to outline the properties of the hydrofluorocarbon solvent 1,1,1,2-tetrafluoroethane (R-134a) that make it an attractive proposition for the extraction of natural products and to highlight some of extracts that may be obtained. 

Polymer Synthesis using Hydrofluorocarbon Solvents Synthesis of Cross-Linked Polymer Microspheres by Dispersion Polymerization in R134a... 

Production of hydrogen fluoride from reaction of Cap2 with sulfuric acid is the largest user of fluorspar and accounts for approximately 60—65% of total U.S. consumption. The principal uses of hydrogen fluoride are ia the manufacture of aluminum fluoride and synthetic cryoHte for the Hall aluminum process and fluoropolymers and chlorofluorocarbons that are used as refrigerants, solvents, aerosols (qv), and ia plastics. Because of the concern that chlorofluorocarbons cause upper atmosphere ozone depletion, these compounds are being replaced by hydrochlorofluorocarbons and hydrofluorocarbons. 

Ruorocarbon solvent polarity (PJ increases when fluonne is substituted by chlonne or hydrogen, and hydrofluorocarbons can be more polar than their hydrocarbon analogues Notably, = 7 52 and P (1,2 C H4p2) = 7 86 vs... 

Poor solubility in most common organic solvents represents an inherent problem in the synthesis and processing of many high molar mass fluoropolymers. In fact, CFCs and carbon dioxide are the best solvents for amorphous varieties of fluoropolymers. Due to the environmental problems associated with CFCs, the international community is seeking to replace them with more benign compounds such as hydrochlorofluorocarbons and hydrofluorocarbons. However, the environmental problems which will be created by the use of these replacement compounds such as the accumulation of trifluoroacetic acid in the atmosphere clouds this issue [71], Carbon dioxide presents an ideal inert solvent to effect the polymerization of these types of highly fluorinated monomers and obviates the use of solvents that are being phased out because of environmental concerns. 

Tetrafluoroethane is a hydrofluorocarbon (HFC) or hydro-fluoroalkane (HFA) aerosol propellant (contains hydrogen, fluorine, and carbon) as contrasted to a CFC (chlorine, fluorine, and carbon). The lack of chlorine in the molecule and the presence of hydrogen reduces the ozone depletion activity to practically zero. Hence tetrafluoroethane can be considered as an alternative to CFCs in the formulation of metered-dose inhalers (MDIs). It has replaced CFC-12 as a refrigerant since it has essentially the same vapor pressure. Its very low Kauri-butanol value and solubility parameter indicate that it is not a good solvent for the commonly used surfactants for MDIs. Sorbitan trioleate, sorbitan sesquioleate, oleic acid, and soya lecithin show limited solubility in tetrafluoroethane and the amount of surfactant that actually dissolves may not be sufficient to keep a drug readily dispersed. 

Sidebottom H., and J. Franklin The atmospherie fate and impact of hydrofluorocarbons and chlorinated solvents. Pure ondAppl. Chem. 68 (1996) 1757-1769. 

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