NOTES
4410
cules and to account for the side reactions observed upon long irradiation is the reaction of an activated CFRNO molecule with the dimer CFzNO*
+ (CF,)2NONO
---+
(CFa)zNOCF,
+ NOz +
l/i"
We have noticed an extremely slow, dark reaction on a sample of (CF&NONO kept in a stainless steel cylinder for approximately 1 year. The primary product appears to be (CFa)2NN02. This may be an intramolecular rearrangement or a possible dissociation of (CF3)zNONO into (CF&NO and NO radicals and rearrangement upon recombination to form (CF& "02.
The mass spectrum of (CF3)2NON0 has been determined with a Bendix time-of-flight mass spectrometer. A parent ion is not obtained even with a low ionizing voltage. The major peaks are due to CF3+ and NO+. Reasonably intense m/e peaks are obtained at 168 [(CF&NO+] and 149 [CF,N(=CFZ)O+]. The 168 m/e peak further confirms the structure of the dimer as the N-nitritoamine. The failure to obtain a parent ion €or this compound illustrates the relative ease of cleaving the nitrogen-oxygen bond under electron impact. The complete mass spectra and thermal decomposition studies on a series of perfluoro-nitrogen-oxygen compounds will be reported in detail a t a later date. Acknowledgment. The authors wish to thank Drs. P. L. Goodfriend and U. V. Henderson for helpful discussions on this subject. This work was partially supported by Air Force Rocket Propulsion Laboratory, Air Force Systems Command, United States Air Force, Edwards Air Force Base, Calif.
Photolysis of Fluorotrichloromethanel by Dana Marsh and Julian Heicklen Aerospace Corporation, El degundo, California (Received July f23, 1966)
As a continuation of our program on fluorocarbon oxidations, we have examined the photochemistry of CFC& in the presence of 0 2 or NO. Earlier workz on the oxidation of CF3 radicals had shown that the only carbon-containing product was CF20. We were curious to see if CFClz radicals would oxidize in an analogous manner. The Journal of Physical Chemistry
Upon exposure to the 2138-A. radiation of a zinc lamp, pure CFC13 showed no evidence of reaction as determined by in situ infrared analysis. This can be explained by the sequence of reactions CFCls
+ h~
--f
CFClz
+ C1
2CFClz ---j (CFClz)2
(11 (2)
+ M Clz + M C1 + CFClz CFC1, CFClz + Clz --+CFCh + C1 2C1
-+P
(3)
(4) (5)
When a small amount of molecular chlorine has been formed by reaction 3, then reaction 5 becomes important and inhibits product formation. The products never reach sufficient concentrations to be detected. Mixtures of CFCl3 and NO were photolyzed, and infrared product bands were observed at 5.56, 6.19, and 8.8 p . The band at 5.56 p is the intense band of NOCl.3-5 Its growth was nonlinear and diminished with increasing exposure. It continued to grow, though very much more slowly, after exposure was terminated. It was clear that this band could not be associated with the same molecule as the other two bands. It is difficult to understand why NOCl formation should be inhibited with exposure time. More likely, the nonlinearity of the 5.56-p band reflects a deviation from Beer's law similar to that for Notazb The optical density of bands at 6.19 and 8.8 M grew linearly with exposure time, and their ratio was invariant for all runs. Presumably, these two bands can be associated with CFCLNO. The relative quantum yields of formation of CFClzNO are reported in Table I. Ratios of CFCls and NO used were such that the absorption of the radiation by NO was unimportant. Within the experimental error, G(CFClZNO)is unchanged by variations in either the CFCL or the NO pressures, thus suggesting that the absolute quantum yield is indeed unity. The mechanism that explains the result is CFClz NO
+ NO
+ Clf
--t
CFCIzNO
M--+NOCl+
M
(6)
(7)
(1) This work was supported by the U. 8. Air Force under Contract No. AF 04(695)-469. (2) (a) H. S. Johnston, private communication (1965); (b) J. Heicklen, Aerospace Corp. Report TDR-469(5250-40)-12, May 1965. (3) L. P. Kuhn and C. Butkiewicz, J . Phys. Chem., 65, 1085 (1961). (4) W. Q. Burns and H. J. Bernstein, J . Chem. Phys., 18, 1670 (1950). (5) P. J. H. Woltz, E. A. Jones, and A. H. Nielsen, ibid., 20, 379 (1952)-
NOTES
4411
The oxidation is indeed analogous to that for CF, radicals.2b There are two mechanisms that can explain the oxidation. One mechanism is
Table I: Photolysis of CFCla and NO Mixtures (X 2138 A., T = 24O, Io = 1.0 x 10'6 quanta/cm.3 min.) (NO),
(CFCla),
a
mm.
mm.
a(CFClBNO)
18.5 210 226 210 260
2.0 2.2 20 20 60
0.89
CFCl2
+
2c10
0.96 0.98 1.06 1.09
-+- CFClO
0 2
--j
Cl2
+ 02
CFClz
+
0 2 --ic
CFClzOz
+ 2CFClO + Clz
2CFC1202 +2CFClz0
---f
2c1
(8)
followed by (7). The molecular chlorine would not be detected as it has no infrared absorption bands. Mixtures of CFCla and 0 2 were photolyzed, and three infrared bands were found a t 5.35, 5.46, and 9.08 p . These bands correspond to those reported for CFC10.6 Undoubtedlly, Cl2 also was produced. The optical density of the 5.35-p band was monitored, and it grew linearly with exposure time. From the results, shown in Table 11, it can be seen that a(CFC10) is Table 11: Photolysis of CFCL and O2Mixtures ( A 2138 A,, 5" = 24', lo = 1.0 X 1 O I 6 q ~ a n t a / c m min.") .~
mm.
(On), mm.
20.5 20 190 190 250 185b
20.5 200 19.5 290 200 230
(CFCla),
(10)
(11)
which could be followed by
The slight growth of NOCl after exposure might result from the photolysis of Clz from the overhead fluorescent room lights
+ hv
(9)
The addition of HI would not alter the CFClO yield. The other mechanism involves the addition reaction
Average value assumed to be 1.00.
Clz
+ C10
Q(CFCl0)
0.94 0.98 1.02
1.01 1.04
0.89
a IO calculated assuming average value of O(CFC10) = 1-00. 2.5 mm. of HI present for this run.
invariant to the pressures of the reactants. The incident intensity Io was estimated by assuming the average value of QI(CFC10) to be unity. I n one run, a small amount of HI was added (the HI absorbed only a few per cent of the radiation). The yield of CFClO was unaffected, but an additional unidentified product band a t 9.46 p was found. When mixtures of CFCl3 and HI without oxygen were photolyzed, the peak at 9.46 p was still observed, and it was the only product peak.
2CFC120 ---f
0 2
(12) (13)
However, H I should scavenge the CFClzOz radical to give CFCl2O2H. Then the results could be explained only if CFClzO2H were a very reactive intermediate which immediately decomposed to CFClO and HOC1.
Experimental Section Trichloromonofluoromethane (Genetron 11) was obtained from the Allied Chemical Co. and showed about 2% impurities on analysis by gas chromatography. It was used directly after degassing twice a t - 196". At the conclusion of photolysis, the impurity was still present at the same concentration, thus indicating that it did not enter the reaction. Nitric oxide, oxygen (extra dry grade 99.6% pure), and anhydrous H I were obtained from the Matheson Co. All were degassed twice a t -196". The NO was further purified by warming to -186" and collecting the volatile fraction, thus removing traces of N20, NOz,and water. The infrared analyses were performed in situ in a Perkin-Elmer Model 13 Universal spectrometer. A T-shaped cell was used having 11.5-em. infrared and 10.7-em. ultraviolet path lengths. The ultraviolet light entered the stem of the T through a silica window. The top of the T had sodium fluoride windows a t each end and was situated in the infrared beam. A low-pressure resonance zinc lamp obtained from the North American Phillips Co. was used. The 2138-A. line was responsible for photolysis. The absorption coefficients, to base 10, were determined for CFC13, NO, and HI at 2138 A. in a Cary Model 15 spectrophotometer and are 1.00 X 0.24 X and 12.8 X cm.-lmm.-l, respectively. The infrared absorption coefficient was estimated by passing samples of CFClO of known absorbance (6) A. H. Nielsen, T. G. Burke, P. J. H. Woltz, and E. A. Jones, J. Chem. Phys., 20, 597 (1952).
Volume 60,Number l d
December 1966
NOTES
4412
through a n F & M chromatograph with a silica gel column and by measuring the COz peak. Fluorocarbonyl compounds decompose quantitatively to C02 on this column; thus, the COZ corresponds to the CFClO introduced. The absorption coefficient, to base 10, a t 5.35 p is 0.019 cm.-I mm.-l. Assuming the CFClO and the CFC12N0 yields to be unity in t.he CFCL-02 and the CFCl,-NO photolyses, respectively, yields values 0.0087 and 0.012 mm.-I for the absorption coefficients, to base 10, for the 6.19- and 8.8p bands of CFCI2NO,respectively.
Acknowledgment. The authors wish to thank Mrs. Barbara Peer for assistance with the manuscript.
Self-Diffusion Coefficients of Water by Jui H. Wang Kline Chemistry Laboratory, Yale University, New Haven, Connecticut (Received August 2, 1965)
The self-diffusion coefficients of water are of interest in many physicochemical and biological studies. A series of measurements of the self-diff usion of liquid water with HIzO1*as tracer by means of the controlled-stirring, open-capillary method was carried out in 1954 in connection with our study of the solutions of proteins1 and electrolytes.2 I n view of the frequent use by other workers of the two published self-diff usion coefficients of water, it seems desirable to report the other values determined in our earlier series of measurements. The experimental details were already described in an earlier p ~ b l i c a t i o n . ~The OIs atom per cent in the diffusion samples varied from 0.5 to 1.5%. The temperature was controlled to within i0.01". The results are summarized in Table I. The constancy of Dq/T shows that the effective volume of the diffusing species remains constant be-
tween 5 and 25". Therefore, in spite of the tetrahedrally hydrogen-bonded structure of waterl416 it is entirely adequate to describe its self-diffusion in terms of the movement of individual H20 molecules.6 A linear plot of In D vs. 1/T gives an apparent activation energy of 4.8 kcal./mole. Since each hydrogen bond is shared between two water molecules, this apparent activation energy is large enough to rupture completely two hydrogen bonds per activated molecule. For a polar liquid with loose-packed structure such as the ice-like structure of water, self-diffusion and dielectric relaxation may involve essentially the same activation mechanism. If this is the case, then the dielectric relaxation time r and self-diff usion coefficient D should be related by the simple equation, D = X2/r, where X is the average distance between two successive equilibrium positions of a diffusing molecule. Since the density of water at 25' is only 0.3%smaller than that a t 5") X2 should remain practically constant in this temperature range. The dielectric relaxation data of Collie, Hasted, and Ritson' enable us to compute X2 as listed in Table 11. Using the average of the above values of PT = X2, we obtain a mean jumping distance of 3.7 A. for self-diffusion in liquid water. This value compares interestingly with the observed 0-0 distances in ice I which are 2.76 A. for the nearest neighbors and 4.51 8. for the next nearest neighbors. Table I1 Temp.,
7
x lo1',
DT
x
1016,
C.
880.
cm.2
5
9.43 7.96 6.87 5.23
13.4 13.3 13.5 13.4
10 15 25
Experimentally, the constancy of D r / T and D r with respect to T enables one to estimate with reasonable accuracy both D and 7 at other temperatures from the viscosity data of water by either interpolation or even short extrapolation of these values.
Table I
OC.
Number of measurements
Self-diffusion coefficient of water, D X 105, cm.s/sec.
Viscosity, 1 X 108, poise
5.00 10.00 15.00 25.00
8 6 8 6
1.426 f 0.018 1.675 f 0.025 1.97 i.0.020 2.57 i.0.022
15.188 13.077 14.404 8.937
Temp.,
The Journal of Physical Chemistry
DdT
x
1010
7.77 7.73 7.79 7.70
(1) J. H. Wang, J. Am. Chem. SOC., 76, 4755, 6423 (1954). (2) J. H. Wang, J . Phys. Chem., 58, 686 (1954). (3) J. H. Wang, C. E. Anfinsen, and F. M. Polestra, J. Am. Chem. SOC.,76, 4763 (1954). (4) J. D. Bernal and R. H. Fowler, J. Chem. Phys., 1, 515 (1933). (5) L. Pauling, J. Am. Chem. SOC.,57, 2680 (1935). (6) J. H. Wang, {bid., 73,510 (1951). (7) C. H. Collie, J. B. Hasted, and D. M. Ritson, Proc. Phys. SOC. (London), 60, 145 (1948).
