Producing hydrofluoro compounds by hydrogenolysis of iodides

Details Producing hydrofluoro compounds by hydrogenolysis of iodides Producing hydrofluoro compounds by hydrogenolysis of iodides

1993-04-07

2003-02-25

Richter, Johann (Department: 1621)

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

Organic compounds

Halogen containing

Reexamination Certificate

active

06525231

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the production of compounds containing fluorine-substituted carbon atoms, and more particularly to the production of hydrofluoro compounds containing multiple carbon atoms and/or both carbon and sulfur atoms.
BACKGROUND OF THE INVENTION
Multicarbon compounds and carbon-sulfur compounds which contain hydrogen and fluorine but no chlorine, have recently been the subject of renewed interest as environmentally desirable compounds for use as solvents, blowing agents and refrigerants. Among these compounds are certain hydrofluorocarbons (i.e., compounds containing only carbon, hydrogen and fluorine) which have typically been produced using catalytic processes for hydrogenolysis and/or hydrogenation of saturated or unsaturated compounds containing both chlorine and fluorine. Certain supported precious metal catalysts are among those considered particularly suited for catalyzing the reactions. British Patent Specification No. 1,578,933 uses a process for the manufacture of CF
3
CH
2
F or CHF
2
CHF
2
by the hydrogenolysis of an appropriate haloethane (e.g., CF
3
CCl
2
F) over a hydrogenation catalyst such as palladium supported on carbon or alumina. Conventional hydrogenolysis of this type can be used to convert CF
3
CCl
2
F to a product mixture including CF
3
CHClF and CF
3
CH
3
in addition to tetrafluoroethane.
Precious metal catalysts such as palladium are expensive and can deactivate during the course of catalyzed reactions. Replacement and/or regeneration of such catalysts can thus add to the cost of the catalyzed reaction. Also, the use of chlorine-containing reactants such as CF
3
CCl
2
F and the production of chlorine-containing products such as CF
3
CHClF can present handling and disposal concerns.
Iodine or hydrogen iodide have been used in conjunction with the reaction of selected fluorine-containing compounds. For example, U.S. Pat. No. 2,844,636 discloses a process for the manufacture of 1,1,2,3,4,4-hexafluorobutane by reacting perfluoro-cyclobutene with hydrogen, using elemental iodine as a catalyst. In this process not only is there hydrogen addition at the double bond, but also cleavage and hydrogenation at the —CF
2
—CF
2
— single bond to give the substituted normal butane. U.S. Pat. No. 5,097,082 discloses a process for producing saturated halohydro-carbons containing fluorine which comprises the step of reacting certain saturated or olefinic compounds at an elevated temperature with hydrogen in the presence of at least one material selected from the group consisting of iodine and hydrogen iodide, or with hydrogen iodide.
SUMMARY OF THE INVENTION
A process is provided in accordance with this invention for producing a compound of the formula RCFZH wherein R is selected from the group consisting of SF
5
, CF
2
SF
5
and R
f
CF
2
Y, R
f
is a perfluoroalkylene group containing from 1 to about 12 carbon atoms and optionally containing one or more ether oxygen atoms, Y is selected from H, F, and SF
5
and Z is selected from CF
2
CF
3
, CF
3
and F, by reaction of an iodide compound of the formula R′CFZI with hydrogen at an elevated temperature, wherein wherein R′ is selected from the group consisting of SF
5
, CF2SF
5
and R
f
CF
2
X and X is selected from H, F, SF
5
, and I, provided that when Y is F, X is F, when Y is SF
5
, X is SF
5
and when Y is H, X is H or I.
DETAILS OF THE INVENTION
This invention provides a process for producing monohydro and dihydro compounds from corresponding monoiodo and diiodo compounds. The monoiodo and diiodo reactants of this invention include compounds with multiple adjacent carbons (i.e., C—C bonds) and/or carbon adjacent to sulfur (i.e., C—S bonds). The monoiodo and diiodo reactants are reacted in accordance this invention essentially without cleavage of these carbon-carbon and carbon-sulfur bonds. The iodide compound reactants of this invention contain an iodine which is either on a difluoro-substituted carbon (i.e., Z is F) or on a monofluoro-substituted carbon adjacent to a CF
3
or C
2
F
5
group (i.e., Z is CF
3
or CF
2
CF
3
). The diiodo compounds all contain at least one iodine which is on a difluoro-substituted carbon. Preferably Z is F, especially when R′ is R
f
CF
2
X.
The monoiodo and diiodo compounds which are reacted in accordance with this invention include (where R′ is R
f
CF
2
X and X is H, F or I) any perfluoroalkyl iodide, perfluoroalkyl diiodide or &ohgr;-H-perfluoroalkyl iodide containing from 3 to about 14 carbon atoms and optionally containing one or more ether oxygen atoms. The perfluoroalkylene group, R
f
, may be branched or unbranched. Examples of perfluoroalkylene groups which do not contain ether oxygens include for example, —CF
2
—, —CF
2
CF
2
—, —CF
2
C(CF
3
)F—, —CF
2
CF
2
CF
2
—, —CF
2
C(CF
3
)
2
— and —CF
2
CF
2
CF
2
CF
2
—. Examples of perfluoroalkylene groups which contain ether oxygens include for example, —CF
2
OCF
2
—, —CF
2
CF
2
OCF
2
—, —CF
2
OCF
2
OCF
2
—, —CF
2
OCF
2
CF
2
OCF
2
—, —CF
2
CF
2
OCF(CF
3
)CF
2
OCF
2
—, and —CF
2
OCF
2
CF(CF
3
)OCF
2
CF
2
OCF(CF
3
)CF
2
OCF
2
—.
Preferred iodides include mono- and diiodides of the structures CF
3
R
f
CF
2
I and ICF
2
R
f
CF
2
I, where R
f
is C
1
to C
10
perfluoroalkylene, branched or unbranched, and optionally containing one or more ether linkages. Most preferred are iodides of the linear structures F(CF
2
)
n
I and I(CF
2
)
n
I where n is an integer from 3 to 12. Examples include I(CF
2
)
4
I, I(CF
2
)
6
I, F(CF
2
)
4
I, F(CF
2
)
6
I, and F(CF
2
)
8
I.
Perfluoroalkyl iodides may be prepared by the addition of either trifluoroiodomethane or pentafluoroiodoethane to tetrafluoroethylene as disclosed by R. N. Haszeldine, J. Chem. Soc., pp. 3761-3768 (1953). Perfluoroalkyl diiodides containing an even number of carbon atoms may be prepared by the addition of 1,2-diodoperfluoroethane to tetrafluoroethylene as disclosed in Houben-Weyl, “Methoden Der Organische Chemie” Band V/4, pp. 653-655 (1960). In a similar manner perfluoroalkyl diiodides containing an odd number of carbon atoms may be prepared by the addition of 1,3-diodoperfluoropropane to tetrafluoroethylene. &ohgr;-H-perfluoroalkyl iodides may be prepared by the reaction of an &ohgr;-H-perfluoroalkyl acid chloride with potassium iodide as disclosed by C. G. Krespan, J. Org. Chem., Vol. 23, pp. 2016-2017 (1958). Perfluoroalkyl iodides containing C
3
to C
14
carbon atoms and optionally containing one or more ether oxygens may be prepared as disclosed in U.S. Pat. No. 4,275,226, which is hereby incorporated herein in its entirety by reference (see in particular col. 2, lines 46-65).
The monoiodo compounds which are reacted in accordance with this invention also include carbon-sulfur compounds having a pentafluoro sulfur group. Examples include SF
5
CF
2
I and SF
5
CFICF
3
(i.e., R′ is SF
5
) and SF
5
CF
2
CF
2
I (i.e., R′ is CF
2
SF
5
and Z is F). SF
5
CF
2
I has been prepared by reaction of the silver salt of SF
5
CF
2
CO
2
H with iodine as disclosed by Bekker, et al. in IZV. Akad. Nauk SSSR, Ser. Khim., pp. 2738-2741 (1970). SF
5
CFICF
3
has been prepared by reaction of SF
5
CF═CF
2
with a mixture of iodine and IF
5
as reported by Gard and Woolf in J. Fluorine Chem., Vol. 1, pp. 487-492 (1971/2). Longer chain SF
5
-terminated reactants can generally be prepared in a manner analogous to CF
3
-terminated compounds. SF
5
-substituted iodofluoroalkanes containing an even number of carbon atoms (SF
5
(CF
2
CF
2
)
n
I, where n is an integer from 1 to about 6) may be prepared by reacting S
2
F
10
with CF
2
ICF
2
I or with I
2
and tetrafluoroethylene as disclosed by Hutchinson in J. Fluorine Chem., Vol. 3, pp. 429-432 (1973/4).
The hydrogenolysis reaction of this invention may advantageously be accomplished in the absence of hydrogenation catalysts. The term “hydrogenation catalysts” is used herein in the ordinary sense, to signify conventional metal-based hydrogenation catalysts which are in themselves known. Examples of hydrogenation catalysts include nickel or other metals of Group VIII of the Period

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