Aerosol direct fluorination : syntheses of perfluoroethers and perfluoroesters

A series of perfluoroesters and perfluoroethers has been synthe sized utilizing the aerosol direct fluorination technique. In all cases the starting material was the hydrocarbon analog. The following perfluorinated esters and ethers were synthesized: F-1,2-dimethoxyethane, F-bis-2-methoxyethyl ether, F-triethylene glycol dimethyl ether, F-tetraethylene glycol dimethyl ether, F-bornyl methyl ether, F-methyl 2-methoxypropanoate, F-methyl 2,2-dimethylpropanoate, F-methyl 2-methylpropanoate, F-methyl propanoate, F-ethyl propanoate, F-isopropyl propanoate and F-tert-butyl propanoate. In the case of the fluorination of methyl 2-methoxypropanoate the major product was F-2-methoxypropanoyl fluoride, which is a result of ester cleavage. However ester cleavage was not a major problem in the other perfluoro ester syntheses. The purpose of the study of the perfluorinated ester synthesis was to determine what effects different groups attached to the ester linkage would have on cleavage. A one-step synthesis by aerosol direct fluorination producing monofluorobenzene from benzene was carried out. To determine the limitations of aerosol direct fluorination, a compound containing highly hindered hydrogens, 2,4-dimethylpentane, was fluorinated and this resulted in a mixture of mono- and dihydryl isomers where the remaining hydrogens are those that are highly hindered. This technique was also shown to produce a perfluorinated epoxide, F-cyclohexene oxide, from its hydrocarbon analog. All compounds were characterized by infrared spectroscopy, electron-impact and chemical ionization mass spectrometry and both ¹⁹F and ¹H nuclear magnetic resonance spectroscopy.

While effluent concentrations of the desired products were usually high, the throughput yields based on hydrocarbon injected into the reactor system were often low. A series of experiments was conducted to determine where losses in the system occur. A series of modifications and improvements were made to enhance through put yields.