Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Patent
1994-09-14
1996-08-13
Siegel, Alan
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C07C 1708
Patent
active
055457711
DESCRIPTION:
BRIEF SUMMARY
This application is based on International application PCT/JP93/00301 filed Mar. 12, 1993.
Technical Field
The present invention relates to a process for preparation of gem-difluoroalkanes.
Background Technique
CFCs have hitherto been frequently used as cleaning agent, refrigerant, blowing agent or the like, but in accordance with a rise of concern about the problem of ozone layer depletion in recent years, it is internationally decided to restrict their use, and alternatives for CFCs are vigorously developed.
Fluorine compounds, as such or in the formation of polymers, can be expected as raw materials for highly functional materials in various fields including electronic industry and medical field.
In these circumstances, gem-difluoroalkanes represented by the general formula RCF.sub.2 R' wherein R and R' denote hydrogen atoms or hydrocarbon residues optionally having substituent(s) are expected for uses as alternatives for CFCs, intermediates for syntheses of alternatives for CFCs, or raw materials for highly functional materials. For instance, 2,2-difluoropropane is used as a foaming agent, a refrigerant or the like (DE 3903336A and Japanese Laid-Open Patent Publication 17139/1990).
A process which comprises reacting an alkyne with hydrogen fluoride is known for preparation of a gem-difluoroalkane (U.S. Pat. No. 2,287,934 and J. Am. Chem. Soc., 64, 2289 (1942)).
However, there were problems in the above process. Alkynes, particularly low boiling alkynes such as propyne and butyne used as raw materials are extremely unstable substances, and hard to handle, and it takes much labor and costs in purification to obtain them in a pure form. In addition, the yields of the desired products are unsatisfactory and the process was disadvantageous in an economical aspect.
To solve these problems, a process is considered, which comprises using a crude alkyne containing a polymerizable olefin as an impurity, obtained as a distillate after naphtha cracking. Although this process is excellent in the points of economical efficiency and easiness in handling, there are problems that oligomers tend to be accessorily produced from the polymerizable olefins, and it is not easy to remove them by filtration or distillation.
Thus, since a crude alkyne is economically obtained as a distillate after naphtha cracking, a process is desired for preparing a gem-difluoroalkane simply and in good yields using the crude alkyne as a raw material, but the desire has not so far been attained.
Disclosure of Invention
The present invention has been made in view of the above circumstances, and aims at solving the problems in the usual processes and providing a process for preparing gem-difluoroalkanes more economically from crude alkynes.
According to the present invention, a process for preparation of a gem-difluoroalkane is provided which comprises -30.degree. to 30.degree. C. to a crude alkyne having 3 or 4 carbon atoms containing a polymerizable olefin as an impurity, and distill the mixture to remove the polymerizable olefin, alkyne having 3 or 4 carbon atoms obtained in the above step to synthesize the gem-difluoroalkane, and gem-difluoroalkane.
In the step (A) of the present invention, it is performed to add a fluorinated alkane having a boiling point of -30.degree. to 30.degree. C. to a crude alkane having 3 or 4 carbon atoms containing a polymerizable olefin as an impurity, and distill the mixture to remove the polymerizable olefin.
The crude alkyne can readily be obtained generally as a distillate after naphtha cracking, and contains an alkyne having 3 or 4 carbon atoms corresponding to the raw material of the desired gem-difluoroalkane. These alkynes include, for example, propyne, 1-butyne, 2-butyne.
The term "alkyne" in the present invention is intended to include an olefin such as allene or 1,2-butadiene which produces the same product as in propyne or 1-butyne by contact with hydrogen fluoride.
The impurity is a polymerizable olefin accompanying the alkyne, and includes, for example, a monoolefin such as ethylene, propy
REFERENCES:
patent: 2287934 (1938-10-01), Grosse et al.
Grosse, et al., J. Am. Chem. Soc., (1942), vol. 64, 2289-2291.
Imai Yasuo
Mitsuda Yasuhiro
Yamada Toshiro
Nippon Zeon Co. Ltd.
Siegel Alan
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