Fluorinated alkyl or alkylether 1,2,4 oxadiazole compounds are prepared by cyclizing the corresponding alkyl or alkylether imidoyl amidoximes in vacuo or in an inert atmosphere at a temperature within the range of 40 C to 100 C. for a period of 8 to 144 hours in the presence of an acid compound which can accept ammonia to form a salt. The imidoyl amidoximes usable in this process are either polymeric or nonpolymeric. The products, when polymeric, have excellent heat, chemical and solvent resistance

Ito, T. I.

Kratzer, R. H.

Paciorek, K. J. L.

Rosser, R. W.

English

NASA Technical Reports Server

United States Patent [191 
Kratzer et al. 
[54] PREPARATION OF PERFLUORINATED 
1,2,4-OXADIAZOLES 
[76] Inventors: Robert A. Frosch, Administrator of 
the National Aeronautics and Space 
Administration, with respect to an 
invention of Reinhold H. Kratzer, 
Irvine, Calif.; Kazimiera J. L. 
Paciorek, Corona del Mar, Calif.; 
Thomas I. Ito, Fountain Valley, 
Calif.; Robert W. Rosser, San Jose, 
Calif. 
[21] Appl. No.: 163,838 
E221 Filed: Jun. 27, 1980 
[51] Int. C1.3 ..................... C07D 271/06; C08G 73/06 
[52] U.S. C1. .................................... 548/131: 528/401: 
4,316,035 
[45] Feb. 16, 1882 
~561 References Cited 
U.S. PATENT DOCUMENTS 
4,145,524 3/1979 Frosch ................................ 548/131 
OTHER PUBLICATIONS 
Clapp, Advances in Heterocyclic Chemistry, vol. 20, 
(Academic Press, 1976), pp. 66-71. 
Primary Examiner-Alton D. Rollins 
Attorney, Agent, or Firm-DarreUl G. Brekke; John R. 
Manning 
ABSTRACT 
Fluorinated alkyl or alkylether 1,2,4-oxadiazole com- 
pounds are prepared by cycliznng the corresponding 
alkyl or alkylether imidoylamidoximes in vacuo or in an 
inert atmosphere at a temperature within the range of 
40" to loo" C. for a period of 8 to 144 hours in the 
presence of an acid compound which can accept ammo- 
nia to form a salt. The imidoylamidoximes usable in this 
process may be either polymeric or nonpolymeric. The 
products, when polymeric, have excellent heat, chemi- 
cal and solvent resistance 
[571 
......... 
528/422; 564/229 
Field of Search ................................ 528/401, 131 4 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=19820020477 2020-03-21T17:12:10+00:00Z
4,3 16,035 
I I 
PREPARATION OF PERFLUORINATED 
1,2,4-OXADIAZOLES 
ORIGIN OF THE INVENTION 5 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 85-568 10 
(72 Stat. 435; 42 U.S.C. 2457). 
TECHNICAL FIELD 
This invention relates to perfluorinated 1,2,4- 
oxadiazoles and to an improved process for making l 5  
them. 
BACKGROUND ART 
20 Heat and chemical resistant polymers characterized 
by perfluorinated segments joined by I,2,4-oxadiazole 
linkages have been disclosed by Rosser et al. in U.S. Pat. 
No. 4,145,524. These polymers are made by a condensa- 
tion process involving a perfluorinated diamidoxime, 
Rf[C(NH2)=NOH]2. The condensation is carried out 25 
at a temperature within the range of 100" to 250" C., 
preferably between 130" and 200" C. either in vacuo or 
in an inert atmosphere, to yield gaseous products and 
polymers of the formula 
30 
in which x is of a magnitude commensurate with a mo- 
lecular weight range 3,000 to 50,000. The diamidoxime 
from which these polymers are made is obtained origi- 
nally by the following reaction which normally takes 40 
place at ambient temperature: 
RjCN)2 + H2NOH-+R[C(NH2)=NOH]2 
45 For many applications, it would be advantageous to 
prepare the 1,2,4-oxadiazole polymers by a more articu- 
lated process that could be better controlled and could 
yield improved polymers. 
which 1,2,4-oxadiazoles can be synthesized at tempera- 
tures significantly lower than those used in the art. 
Another object is to provide a process which minimizes 
or avoids the side reactions and the partial decomposi- 
tion of the reactants that lead to shorter polymeric 5 5  
chains and to random creation of linkages other than 
oxadiazole linkages. Still another object is to provide a 
process capable of higher yields than the processes of 
the art. 
DISCLOSURE OF T H E  INVENTION 
These and other ojbects of this invention have been 
achieved by heating an imidoylamidoxime at tempera- 
tures within the range of 40" to 100" c. for a period of 65 
8 to 144 hours in the presence of an acid compound 
which acts as an ammonia acceptor. The reaction in- 
volved is: 
An object of this invention is to provide a process by 50 
60 
2 
The imidoylamidoximes that can be so treated can be 
either simple perfluorinated compounds containing 
only one imidoylamidoxime group or they can be poly- 
meric substances containing many such imidoylamidox- 
ime groups as linkages. 
The imidoylamidoximes have been disclosed in co- 
pending application Ser. No. 163,839, filed June 27, 
1980. They are produced by allowing to react together 
at temperatures within the range of 20" to 70" C. a per- 
fluorinated alkyl or alkylether nitrile with a perfluori- 
nated alkyl or alkylether amidoxime as illustrated by the 
following reaction: 
When the nitrile and the amid'oxime compounds se- 
lected are bifunctional, oligomeric or polymeric prod- 
ucts will be yielded by reactions I and 11, depending on 
actual reaction conditions employed. 
DETAILED DESCRIPTION O F  THE 
INVENTION 
Cyclization reaction I is carried out in an inert atmo- 
sphere or in vacuo, preferably at temperatures within 
the range of 40° to 100" C. in the presence of an acid 
compound that acts as an ammonia acceptor. Usable 
compounds for this function include organic acids, inor- 
ganic acids, anhydrides, acyl and aryl halides, and more 
specifically, fatty acids, fluorinated fatty acids, perfluo- 
rinated alkylether acids such as C2F5(0CF2CF2)- 
furic acid, phosphoric acid, phosphorus pentoxide, and 
the like. 
The substituents Rj-and Rf in the nitriles and amidox- 
imes used to carry out the present invention can be 
identical or different and are selected (a) from the 
monovalent perfluoroalkyl and perfluoroalkylether 
radicals represented by the general formulas: 
C3F70[CF(CF3)CF20InOCF(CF3)-, or when dini- 
triles and diamidoximes are required, (b) from bivalent 
radicales such as -(CX&-, arylene, --CFY(OCFz 
CFY),0(CX2)pO(CFYCF20)nCFY-, and the like, in 
which p ranges from 2 to 8 when X is fluorine and 2 to 
18 when X is hydrogen, Y is fluorine or a trifluoro- 
methyl group or an assortment of such substituents, and 
m+n ranges from 2 to 7. 
A few specific embodiments will now be provided to 
further illustrate the invention in operational detail. 
These examples are not intended to be limiting, unless 
otherwise specified. 
EXAMPLE 1 
The amidoxime C3F70CF(CF3)CF20CF(CF3)C(- 
=NON)NH2 (1.00 g, 1.97 mmol) and the nitrile 
CjF70CF(CF3)CN (1.50 g, 4.82 mmol) were sealed in 
vacuo and heated at 50" C. for 89 hours. After opening 
the container and removing the excess nitrile (2.81 
mmol) in vacuo at 50" C.,, the corresponding 
nCOOH, C3F70[CF(CF3)CF20]nCF(CF3)COOH, SUI- 
G F 2 n  + 1-7 C2F5(0CF2CF2),0CF2-, 
4,316,035 
3 4 
imidoylamidoxime ( C i 5 H 3 F 2 8 N 3 0 4 )  was obtained in the 
pure state in quantitative yield, as determined inter alia 
by elemental analysis. 
EXAMPLE 2 
4 hours, a quantitative yield of the corresponding po- 
lyoxadiazole was obtained. Analysis of the product 
showed an elemental content of 22.44% C ,  0.56% H, 
62.87% F, and 3.30% N substantially agree with con- 
5 tents calculated for formula 
The bisamidoxime H2N(H0N=)CCF(CF3- C60.73H5.82F109.3 1N7.89019.22 of the oxadiazole polymer. 
The viscous material had a molecular weight of 2600 
and showed no infrared absorbance at 6 . 0 ~ ~  thus indi- 
) [OCF2CF(CF3) lm-  0(CF2)50[CF(CF3)C- 
F 2 O ] , C F ( C F 3 ) C ( = N O H ) N H 2  in which m+n=3  (0.63 
trile (0.66 g, 0.64 mmol) at 50" C .  for 52 hours with 10 ime linkages. 
stirring. The infrared spectrum of the viscous liquid 
~ ~ ~ ~ ~ ' t ~ ~ g h r a ~ ~ ~ i s ~ i c  ~ ~ ~ ~ ~ c e ~ ~ ~ ~ m i ~ ~ ~ ~ ~ ~  
doxime moieties. No significant nitrile and amidoxime 
product gave: c ,  22.75%; H ,  0.63%; F, 63.03%; and N ,  
a compound with a molecular weight of 4315.99. 
g, 0.60 mmol) was heated with the corresponding dini- cating complete transformation of the imidoylamidox- 
A great advantage of the imidoylamidoxime route to 
1,2,4-0xadiazoles is especially evident in the formation 
of polymers from difunctional nitriles and difunctional 
reaction temperatures that the imidoylamidoximes per- 
tion *' the diamidoximes used in the art u.s. Pat. No. 
4,145,524), resulting in a better polymeric product 
2o which contains fewer shorter chains that would other- 
The imidoYlamidoximes Prepared by the new low 
quantities of the imidoylamidoxime, e.g. temperature condensation process disclosed can serve 
C3F70CF(CF3)CF20CF(CF3)C(- either as chain stoppers or crosslink index diluters in 
=NOH)N=C(NH2)CF(CF3)OC3F7, and a given am- 25 certain polymerization reactions, or, when they are 
monia acceptor were heated at a specific temperature oligomeric or polymeric, they can be converted to use- 
for a given period of time under nitrogen bypass. At the ful polyoxadiazoles of the type described in U.S. Pat. 
conclusion of this procedure, trichlorotrifluoroethane N o .  4,145,524. Such heat and chemical resistant poly- 
(Freon 113) was added to the reaction mixture to form mers, when suitably compounded with fillers, exten- 
a slurry, which was filtered to remove the ammonium 30 ders, and modifiers, can be used in numerous applica- 
salt produced. After removal of the solvent, the oxadia- tions in which high stability, impermeability to liquids 
zole yield was determined by gas chromatography, and gases, and good plasticity are advantageous, e.g. as 
utilizing for compound quantitation, a flame ionization adhesives, caulking compounds, channel sealants, and 
detector, and for compound identification, a mass spec- fuel tank liners. 
trometer. The ammonia acceptor, the reaction condi- 35 It will be readily apparent, furthermore to one of 
tions and the yield Of oxadiazole are shown in the table ordinary skill in the art that many changes and modifi- 
below. cations can be made in the process and the products 
TABLE described, without departing from the spirit and the 
Yield of scope of the following claims. 
absorption could be detected. Elemental analysis of the 15 amidoximes. In such instances, the lower cyc1ization 
3.93%. These values substantially agree with contents mit, avoid the side reactions caused by the decomposi- 
calculated for formula C~0.46H14.89F1~.84Ni2.g9-O25.]4, 
EXAMPLE 3 wise be present. 
In a typical preparation of an oxadiazole, equimolar 
40 It is claimed: 
1. A process for preparing 1,2,4-oxadiazoles and poly- 
Ammonia Temp. Time Period Oxadiazole (a) providing an imidoylamidoxime selected from 
Acceptor ("CJ (Hour) Yield (%) the class consisting of 
17 49 NH2 NOH 1 
20 25 I II 
mers thereof which comprises: 
/"-"\ 
C3F70CF(CF3)C+ ,C CF(CF3)OCF2CF(CF3)0C3F7 
N 
C7F15COOH 70 19 71 45 
C7F15COOH 110 
CF3COOH 70 
R,COOHa 70 24 49 RI-C 
H2S04, conc. 70 24 13 
H3P04, conc. 70 90 52 
p205 70 91 46 50 
'?R/ = C~F,O[CF(CF~)CFZO]ZCF(CF~)- 
As these results demonstrate, a variety of organic and 
inorganic acidic compounds may be employed to ab- 
sorb the ammonia and facilitate the cyclization of the 
imidoylamidoximes. It is also evident that carrying out 
the reaction at a temperature of 1 lo" C .  rather than 70" 
C. can actually lower the yield of 1,2,4-oxadiazole, in 
this instance, from 71% to 49%. 
EXAMPLE 4 
The polyimidoylamidoxime of Example 2 (0.35 g, 
0.33 mmol) was stirred and heated with n-perfluorooc- 
tanoic acid (0.14 g, 0.34 mmol) at 70" C .  for 29 hours. 
Trichlorotrifluoroethane (Freon 113), 5 ml, was added 
to form a slurry, which was filtered to remove the am- 
monium octanoate formed by the reaction. After re- 
moval of the solvent and drying in vacuo at 68" C .  for 
and 
2 
wherein 
60 R1 and R 2  are the same or different and are selected 
from the class consisting of (ti) perfluoroalkyl and 
(b) perfluoroalkyl ether, 
R3 and R 4  are the same or different and are selected 
from the class consisting of perfluoroalkylene and 
65 perfluoroalkylene ether and 
n is a positive integer, 
(b) heating such imidoylamidoximes within the 
range of 40" to 100" C .  for a period of 8 to 144 
5 
4,316,035 
hours in the presence of an ammonia acceptor 
whereby the imidoylamidoxime group or groups 
are converted to 1,2,4-oxadiazole groups. 
2. The process of claim 1 wherein the ammonia ac- 
ceptor is selected from the group consisting of aliphatic 
acids, fluorinated aliphatic acids, alkylether acids, fluo- 
rinated alkylether acids, concentrated sulfuric acid, 
concentrated phosphoric acid and phosphorus pentox- 
ide. 
3. The process of claim 1 wherein the imidoylamidox- 
ime is the compound 1 and the product has the structure 
5 
6 
4. The process of claim 1 wherein the imidoylamidox- 
ime is the polymer 2 and the product has the structure 
10 
' 5  . * * * * *  
20 
25 
30 
35 
40 
50 
55 
60 
65 


Preparation of perfluorinated 1,2,4-oxadiazoles

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server