Method of chlorination of end of fluorine-containing compound

Details Method of chlorination of end of fluorine-containing compound Method of chlorination of end of fluorine-containing compound

2002-03-22

2003-12-02

Richter, Johann (Department: 1621)

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

Organic compounds

Halogen containing

Reexamination Certificate

active

06657094

ABSTRACT:

This application is a 371 of PCT/JP00/06371, filed Sep. 19, 2000.
TECHNICAL FIELD
The present invention relates to a method of chlorinating an end of a fluorine-containing compound having iodine atom at an end thereof and to a novel compound obtained by the method. The compound is useful as a starting material for an ethylenically unsaturated fluorine-containing monomer having a functional group, for example, carboxyl group, nitrile group, or the like at an end thereof.
BACKGROUND ART
Fluorine-containing polymers are used in various forms such as a resin, elastomer, or the like in various fields since they possess specific properties, for example, water- and oil-repellency, heat resistance, chemical resistance, etc.
Further in the field of fluorine-containing resin, functioning thereof is made higher by introducing various functional groups. Also in the field of fluorine-containing elastomer, in order to improve crosslinkability (vulcanizability) and enhance physical properties after the crosslinking, various functional groups which become a crosslinking point are introduced.
For introducing the functional groups, there are, for example, a method of replacing a part of a trunk chain of the fluorine-containing polymer with a group containing a functional group, a method of modifying an end group of the fluorine-containing polymer to a functional group, a method of using a fluorine-containing monomer having functional group as a copolymerizing monomer, and the like.
In those methods, a monomer having a perfluorovinylether (—OCF═CF
2
) exhibits good copolymerizability as the fluorine-containing monomer having a functional group which is used for the copolymerization method. However since an introduction of a double bond is difficult, synthesis thereof is complicated, a yield is not good and as a result, the obtained polymer is very expensive.
Also a compound having iodine atom at an end thereof is used as a fluorine-containing monomer having a functional group for forming a crosslinking point by utilizing such a property that iodine atom bonded to an end carbon atom is radically active. Such a fluorine-containing compound having —CH
2
I group at an end thereof has a very strong bonding force between iodine atom and carbon atom, and therefore the C—I bond has been difficult to cleave. For that reason, with respect to a method for converting —CH
2
I group of the fluorine-containing monomer to other functional group, only some limited reactions such as a de-IF reaction by Zn, or the like have been known.
On the other hand, attempts for chlorinating a fluorine-containing compound having iodine atom at an end thereof have been made (THE 14TH INTERNATIONAL SYMPOSIUM OF FLUORINE CHEMISTRY, pg. 168, 1994). That report says that when a fluorine-containing compound having iodine atom at an end thereof which is represented by the formula (Ia):
Rf
1
CH
2
I  (Ia)
wherein Rf
1
is a polyfluoroalkyl group, is reacted with chlorine gas, there is obtained a compound having iodine and chlorine atoms at an end thereof which is represented by the formula:
Rf
1
CH
2
ICl
2
wherein Rf
1
is as defined above, and the compound returns to the starting compound (Ia) at a temperature around a melting point thereof. Namely, even if the fluorine-containing compound having iodine atom at an end thereof is reacted with chlorine gas, it is impossible to cleave the C—I bond and replace iodine atom with chlorine atom. Furthermore, when heated, the compound is easily decomposed and returns to the starting compound.
An object of the present invention is to provide a novel method of cleaving an end C—I bond of a fluorine-containing compound having iodine atom, namely, a C—I bond at an end thereof and replacing iodine atom with chlorine atom. Another object of the present invention is to provide a novel fluorine-containing compound obtained only by the end-chlorination method of the present invention.
DISCLOSURE OF INVENTION
Namely, the present invention relates to a method of chlorinating an end of a fluorine-containing compound having iodine atom at an end thereof, which comprises reacting a fluorine-containing organic compound having iodine atom at a molecular end thereof and represented by the formula (I):
 RfCX
2
I  (I)
wherein Rf is an organic residue having fluorine atom, X is hydrogen atom or chlorine atom, with a chlorine gas at a temperature within a range of not less than 150° C. and preferably not more than the thermal decomposition temperature of the fluorine-containing organic compound.
Examples of the compound of the formula (I) which the chlorination method can be suitably applied on are a compound in which Rf is an organic residue which may have a functional group (for example, oxygen atom having ether bond, chlorine atom, carboxyl group, hydroxyl group, or the like) free from an effect of the chlorination and is a fluoroalkyl group having 1 to 15 carbon atoms and fluorine atoms having replaced a part or the whole of hydrogen atoms bonded to carbon atoms, and a compound in which Rf is an organic residue represented by the formula (II):
CH
3
OC(═O)C(CF
3
)F[OCF
2
C(CF
3
)F]
m
OCF
2
CF
2
—
wherein m is 0 or an integer of from 1 to 3.
It is preferable that the chlorination reaction of the present invention is carried out under irradiation with light.
According to the end-chlorination method of the present invention, a novel fluorine-containing compound having a chlorinated end and represented by the formula (IV):
CCl
3
CF
2
CF
2
O[C(CF
3
)FCF
2
O]
m
C(CF
3
)FCO
2
CH
n
Cl
3−n
wherein n is 0, 1 or 2, m is 0 or an integer of from 1 to 3, can be prepared. With respect to the compound in which n is 0, an end group —CO
2
CCl
3
is easily decomposed and is converted to a —COCl group.
BEST MODE FOR CARRYING OUT THE INVENTION
A fluorine-containing compound to be chlorinated by the present invention is the compound represented by the formula (I) in which one iodine atom is bonded to carbon atom at an end thereof. An atom bonded to the end carbon atom may be hydrogen atom or chlorine atom. Particularly, from the viewpoint of easiness of synthesis, the chlorination method can be suitably applied on a fluorine-containing compound having hydrogen atom.
The reaction of the present invention proceeds as far as Rf is in principle an organic residue in which at least one of hydrogen atoms bonding to carbon atoms has been replaced with fluorine atom. Rf may have a functional group such as oxygen atom having ether bond, chlorine atom, carboxyl group or hydroxyl group which is free from an effect of the chlorination. However since there is a fear of un-intended replacement of hydrogen atom, etc. with chlorine, preferred is a compound in which Rf is the above-mentioned polyfluoroalkyl group having 1 to 15 carbon atoms. Further since a fluorine-containing monomer precursor having —CH
2
I group can be formed into various fluorine-containing monomers having a functional group by chlorination thereof, the method of the present invention is useful for chlorination of an end of the compound having the organic residue represented by the formula (II).
Examples of the fluorine-containing compound (I) are, for instance,
CF
3
CH
2
I, C
2
F
5
CH
2
I, C
3
F
7
CH
2
I, C
4
F
9
CH
2
I,
(X═F or Cl),
ICH
2
CF
2
CF
2
O[C(CF
3
)FCF
2
O]
m
C(CF
3
)FCH
2
OH,
ICH
2
CF
2
CF
2
O[C(CF
3
)FCF
2
O]
m
C(CF
3
)FCOOH,
ICH
2
CF
2
CF
2
O[C(CF
3
)FCF
2
O]
m
C(CF
3
)FCO
2
CH
3
,
wherein m is 0 or an integer of from 1 to 3.
The fluorine-containing compound may be reacted with a chlorine gas at a temperature of not less than 150° C. and not more than the thermal decomposition temperature of the compound, for example, at a temperature of from 150° to 250° C., preferably from 150° to 180° C. When the reaction temperature is lower than 150° C., the C—I bond is not cleaved sufficiently and the chlorination does not proceed sufficiently. If the reaction temperature is more than 250° C., it is not preferable because a decomposition reaction of the starting compound arises.

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