Process for preparing trifluorohydrocarbon compound

Details Process for preparing trifluorohydrocarbon compound Process for preparing trifluorohydrocarbon compound

1992-06-29

1994-04-12

Evans, Joseph E.

Organic compounds -- part of the class 532-570 series

Organic compounds

Halogen containing

570134, C07C 1710, C07C 1902, C07C 1908

Patent

active

053027647

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Technical Field of the Invention
This invention relates to a process for preparing a trifluorohydrocarbon compound.
2. Background Art
Various fluorine-containing compounds have heretofore been used as medicines, pesticides, detergents and solvents, and as raw materials and intermediates used for the preparation of these materials.
In recent years, to cope with an environmental problem of depletion of the ozone layer caused by Freon.RTM. compounds, especially chlorofluorocarbons, other fluorine-containing compounds have been intensively investigated and developed as substitutes for Freon compounds.
A process is known for preparing the fluorine-containing compounds having a high practical use, which comprises converting a carbon-hydrogen bond of a hydrocarbon compound to a carbon-fluorine bond by using cobalt trifluoride (CoF.sub.3) [see, for example, R. E. Banks, J. C. Tatlow, J. Fluorine Chem., 33, 227(1986)].
However, there are no great differences among the reactivities of the plurality of carbon-hydrogen bonds in the hydrocarbon compound used as the raw material, and therefore, a mixture of various fluorinated compounds having one or more bonded fluorine atoms or many isomers are inevitably produced. In other words, the fluorination reaction is not selective. Thus, a process for selectively fluorinating hydrocarbon compounds by using a cobalt trifluoride is not known.


SUMMARY OF THE INVENTION

In view of the foregoing state of art, an object of the present invention is to solve the problems of the conventional process, and to provide a process by which a fluorine-containing compound can be efficiently prepared with high selectivity.
More specifically, an object of the present invention is to provide a process for the preparation of a fluorine-containing compound wherein a gem-difluorohydrocarbon compound is capable of being partially fluorinated under mild reaction conditions with high selectivity.
In accordance with the present invention, there is provided a process for preparing a trifluorohydrocarbon compound represented by the following formula (2): ##STR2## wherein R is an alkyl group having 1 to 4 carbon atoms, and each of R' and R" is a hydrogen atom, a halogen atom or an alkyl group having 1 to 4 carbon atom, which may have a halogen substituent, represented by the following formula (1): ##STR3## wherein R, R' and R" are as defined above, with cobalt trifluoride.


DETAILED DESCRIPTION OF THE INVENTION

The starting compound used in the process of the present invention is a difluorohydrocarbon compound which is represented by the above formula (1), wherein R is an alkyl group having 1 to 4 carbon atoms, and each of R' and R" is a hydrogen atom, a halogen atom or an alkyl group having 1 to 4 carbon atom, which may have a halogen substituent. As the alkyl groups, there can be mentioned, for example, a methyl group, an ethyl group, an isopropyl group, a butyl group and an isobutyl group. As the halogen atom, there can be mentioned, for example, a chlorine atom and a bromine atom. As specific examples of the difluorohydrocarbon compound of the formula (1), there can be mentioned 2,2-difluoropropane, 2,2-difluorobutane, 2,2-difluoropentane, 3,3-difluoropentane, 2,2-difluoro-1-chloropropane, 2,2-difluoro-1,1-dichloropropane, 3,3-difluoro-1-chlorobutane and 3,3-difluoro-1-chloropentane.
These difluorohydrocarbon compounds of the formula (1) can be prepared by known procedures. For example, there can be mentioned a process wherein a corresponding acetylene compound is reacted with hydrogen fluoride (HF), a process wherein a corresponding carbonyl compound is reacted with a fluorinating agent such as SF.sub.4, and a process wherein a corresponding dichlorohydrocarbon compound is reacted with SbF.sub.4.
The reaction of the difluorohydrocarbon of the formula (1) with cobalt trifluoride (CoF.sub.3) is carried out at a temperature not higher than 150.degree. C., preferably 100.degree. C. to -50.degree. C. Where the temperature exceeds 150.degree. C., a non-selective fluorina

REFERENCES:
patent: 2521626 (1950-09-01), Benning
patent: 2568660 (1951-09-01), Rosen
patent: 2759026 (1956-08-01), McCleary
R. E. Banks, Journal of Fluorine Chemistry, 33 (1986) pp. 227-346.

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