2814
Vol. 70
NOTES
trope, b. p. 56.5-56.8” at 760.5 mm., n * b ~1.4030,found Park’ reported the structure of the CsFs obtained by comparison with a plot of tZ*D/% composition for from pyrolysis of “Teflon” tetrafluoroethylene known mixtures to contain 75 weight % of lower boiling polymer as being a cyclic compound. It is to be 1,2dichloropropene. Ozonization of the above 1,2-dichloropropene-1 in noted that Lewis and Naylor2 report the difficult carbon tetrachloride solution a t 15”followed by treat- oxidation of this product to acidic substances ment with boiling water gave a mixture of hydrochloric, which also suggests the cyclic structure. formic and acetic acids. Treatment with silver hydroxide It has been the purpose of this work now being precipitated silver chloride, oxidized the formic to car~ bonic acid, and thus permitted identification by the reported, to establish the structure of C S Ffirmly Duclaux method of the acetate in the filtrate. and to correct any errors which have appeared in The structure of the 1,2-dichloropropene-l was con- the literature. firmed by addition of chlorine a t 0’ in light from a 200A sample of CaF6 prepared by pyrolysis of tetrawatt clear glass lamp, giving’the saturated 1,1,2,2-tetrafluoroethylene polymer was compared with a chloropropane, b. p. 153-155 a t 774 mm., #D 1.4850. sample of CaFs prepared by the dechlorination of DEPARTXENT OF CHEMISTRY CFsCFCICRCl with zinc and alcohol.3 The MASSACHUSETTS INSTITUTE OF TECHNOLOGY RECEIVED APRIL 16, 1948 marked similarity of these products is shown in CAMBRIDGE, MASSACHUSETTS
-
Table I. TABLE I
The Structure of CjF6 BY EDMOND G . YOUNGAND W n L w
s. MURRAY
Product source
“Teflon” CF*CFClCF&l pyrolysis dechlorination
Studies in this Laboratory involving methods of Molecular weight from commercial feasibility for the synthesis of CFJvapor density
,ci c
151
R 5
10 15 20 25 Time in minutes. Fig. l.-CsF* products: ---,pyrolysis product; dechlorination product; -, mixed. 0
-*-,
153
- 29.6
- 29.8
Boiling point, “C. Freezing point, O C . Mixed freezing point, ‘C.
-156.2
-156.5 156.6
Not only is the mixed freezing point datum excellent evidence for the identity of these products (see Fig. l),but also the infrared absorption curves of these two preparations were found to be identical. The curve for ( 2 8 6 is given in Fig. 2. The maximum a t 5.55 microns is a positive indication of the existence of a double bond in the molecule. Chlorination in light of the two CaFs products (A) from polymer and (B) from CF3CFClCF2Cl gave the corresponding dichlorides which were identical to each other and different from the dichloride obtained (C) by chlorination of H(CF&-
25
1
I
I
15
14
13
I
I
I
12 11 10 Wave length in microns. Fig. 2.-CFsCF=CF*.
CF=CF2 brought to the fore the question Of the propr strUctue Of csF6 as prepared by methods. In particular, Benning, Downing and
1
I
I
9
8
7
I
I
I
6 5.0 4.0
( I ) Benning, Downing and Park, U. S. Patent 2,394.581. (2) Lewis and Naylor, TEXS JOURNAL, e@,I988 (1947). (3) Henne and wdk-, w.,M, 498 (1946).
NOTES
Aug., 1948
2815
in Fig. 4 where both A and B are represented by the single solid line.
- 120
9
TABLEI1 COMPARISON OF CaF&
---_
-\
EI
.e
?;; -130 ‘8
a
M
.s
\
!I
F:
‘\
- 140
\
\
\ \ MIXED I,O-AND 1,3\,DICHLORIDES \
-150
I 0
I
I
I
10 20 Time in minutes. Fig. 3.-CaFsCL products. I
I 15
1
14 Fig. 4.-
30
Product
Molecular weight
A B C D
227.1 226.1 227.8 224.8
Boiling point, OC.
34.5 34.5 35.8 35.6
I
I
I
,
13 12 11 Wave length in microns. ----, 1,3-C1FeClr; , 1,2-CsFsC11.
(4) Downing, Benning and MeH~tnesa,U. 5. Patent 3,884,831.
Mixed freezing point,
QC.
OC.
-132.7 -133.3 -125.4 -126.3
11
-133.0 -146.5 -126.0
The reactions of the 1,2 and 1,3-dichlorohexafluoropropane with zinc in alcohol likewise differ in the products obtained. Although the 1,2-dichloride gave the original CaFB, the 1,3-dichlaride gave a C3FsHC1which has identical infrared absorption with that of CF2HCF2CF2C1. The statement of Park, et d.,” that C F Z C ~ C F ~ Creacted F~C~ with zinc to give a cyclic product must have been based upon the reaction of CFaCFClCF2Cl obtained from pyrolysis of tetrafluoroethylene polymer, which a t that time was thought to be the
I
C14 and (D) by fluorination of CFC12CF2CFC12. This is shown by the data given in Table 11. The freezing point curves shown in Fig. 3 not only verify the identity of A and B but also assure that the dichloride from the pyrolysis product of “Teflon” is not the-same as the 1,bdichloride. This is further corroborated by infrared absorption curves of the three CsFsCf molecules as shown
PRODUCTS
Freezing point,
I
10
9
-
l,&dichloride, to give CFaCF=CF2 boiling a t -30’. There remains no doubt that CSFSprepared by the pyrolysis of tetrafluoroethylene polymer is CF8CF=CF2 and not CF2CFsCFz.
-
LABORATORY E. I. DU PONT DE NEMOURS AND CO. WILMINGTON, DEL. RBCEWED APRIL1,1948
JKKWN
(6) Park,d d, 2nd. Enp. Chem., 8% 354 (1947).
