NOTES
1079
46
Acknowledgments. J. R. Ladd and M. J. Smith prepared the two phenylacetate esters. Mass spectral gas analyses were done by P. C. Noble.
44 42 40
38
Molar Extinction Coefficients of
04Fz
in the
36
Visible Range and a Comparison with
34
Other Oxygen Fluorides'
32
by A, G. Strerig and L. V. Streng
t
30
The Research Instatute of Temple University, Philadelphia, Pennsz/lvania (Received October 3.9,1964) 24
Tetraoxygen difluoride, O4F2, has been synthesized r e ~ e n t l y and ~ , ~ its properties are being studied at the present time. In these studies, the molar extinction coefficients of liquid 04Fz have been determined. The data obtained are presented herewith. Four oxygen fluorides, OF2, OzF2, 03F2,and 04Fz, are known to date. The molar extinction coefficients of OaFz and 03Fz have been reported earlier.4 A literature search showed that there are no quantitative data available on the visible absorption spectrum of liquid OFz, in spite of the fact that this oxygen fluoride has been known since 1927.5 The only known data for OF2 are the qualitative data for gaseous O F Z . ~ Therefore, the molar extinction coefficients of liquid OFz have been measured by us and are being reported here.
e
22
5w
18
u
16
8 14
z 12
z
k
w
10
4
2
0 WAVELENGTH,
Experimental Oxygen Fluorides Used. The 04F2used in this study was prepared in our laboratories directly from the elements by the method described el~ewhere.~The OFz was a commercial product obtained from the Baton Rouge Development Laboratory, General Chemical Division, Allied Chemical Corp. It origindly contained 97.7% by weight OF*, 1.75% 0 2 , and 0.55% COzand was purified by fractional distillation. Pure undiluted liquid OFz and a 0.05 f 0.01 mole/l: 3% 0 2 (by volume, solution of 04F2in liquid CF, liquid) have been investigated a t 77OK. Liquid oxygen was added to carbon tetrafluoride to avoid the solidification of CF4 (m.p. of CF, is 89.2'K.). Solvent. Carbon tetrafluoride (Freon 14) used as the solvent was a commercial product manufactured by E. I. du Pont de Nemours and Co., Inc., Wilmington, Del. It originally contained 99.74 mole % CF4,
+
mp
___)
Figure 1. Visible absorption spectra of oxygen fluorides.
0.02% CClF,, 0.24% air, traces of Con, and 10 p.p.m. of H20. Before use it was treated with fluorine gas a t room temperature and purified by fractional distillation. (1) This paper describes a part of work performed for the Office of Naval Research, Contract Nom 3086(01). (2) A. V. G r o w , A. G. Streng, and A. D. Kirshenbaum, J . A m . Chem. ~ o c . ,83, 1004 (1961). (3) A. G. Streng and A. V. Grosse, First Annual Progress Report for the Office of Naval Research, Contract Nonr 3085(01), Research Institute of Temple University, Philadelphia, Pa., Jan. 3, 1961. (4) A. D.Kirshenbaum and A. G. Streng, J . Chem. Phys., 3.5, 1440 (1961). (5) P.Lebean and A. Damiens, Compt. rend., 185, 652 (1927). (6) A. Glissman and N. J. Schumacher, 2. physik. Chem., B24, 328 (1934).
Volume 69, Number 9 March 1965
NOTES
1080
Apparatus. A Beckman spectrophotometer, Model DU, was used for measurements. The apparatus was fitted with a special cell compartment to permit measurements a t 77’K. Liquid nitrogen was used as a coolant. The cell with samples was immersed into a dewar flask containing liquid nitrogen and having two unsilvered strips for the passage of the light beam. Corrections were made for absorption by the solvent and refrigerant.
Results The molar extinction coefficient was calculated using the equation
D
=
A,Cd
Radiolysis of Frozen Solutions. 11. Sodium Nitrite Ices
by Larry Kevan Department of Chemistry and Enrico Fermi Institute for Nuclear Studies, University of Chicago, Chicago, IZEinois (Received November 13, 1964)
I n a recent study’ it was found that the NOz and NO3 radicals were produced in the radiolysis of sodium nitrate ices a t 77°K. From the concentration dependence and from scavenging data it was postulated that HzO+ was reacting with nitrate ions as in reaction 1. To examine such a, mechanism further, we
HzO+
where D is the absorbance, A , = molar extinction coefficient, in 1. cm.-’ mole-’, c = concentration, in mole/l., and d = cell thickness, 1 cm. The numerical results obtained are presented in Table I. I n Figure 1, the molar extinction coefficient
+ NO3- +NO3*+NO2 + 0
(1) have studied the radiolysis of sodium nitrite ices under similar conditions. Cylindrical ice samples were irradiated a t 77°K. by cobalt-60 y-rays and were subsequently examined by electron spin resonance. The experimental details have been described.
Results and Discussion Table I : Molar Extinction Coefficients of O S and 01Fp in the Visible Range -Molar Wave length, mr
350 360 375 380 400 425 450 475 500 520 550 600 650 675 700 750
extinction coefficient, 1. cm. -1 mole-’OF1 OiFz
0.070 ...
40.8 37.4
0.073
..
...
36.5 44.3
0.061 0.050 0,039 0.029 0.021 0.015 0.010 0.007 0.006 0.006 0.005 0.005
..
43.1
.. 30.3
.. 20.5 1.6 1.4
.. 1.3 1.3
data for 04Fzand OF2 are compared with the earlier reported data for 02FZ and O3FZs6 As can be seen, the absorbance of visible light by OF2 is negligible compared to the other oxygen fluorides. Tetraoxygen difluoride, as expected, has the highest absorbance. Acknowledgment. The authors wish to thank Dr. A. V. Grosse for his helpful suggestions. The Jo~rrnalof Phvsical Chemistry
The initial e.s.r. spectrum a t 77°K. is a composite of the hydroxyl radical spectrum and that due to NOz. The ice sample is then warmed to 145°K. over a 3-min. period and re-examined at 77°K. After this treatment the hydroxyl radical spectrum has decayed while the NO2 spectrum remains unchanged. A comparison of the spectra observed in this fashion in sodium nitrite and sodium nitrate ices is shown in Figures 1 and 2. In Figure 2 the identification of the NO2 anisotropic triplet and NO3 singlet (unresolved triplet) in sodium nitrate ices has been thoroughly discussed.’ Figure 1 clearly shows that NOz is also formed in sodium nitrite ice and that NO3 is not formed. The NO2 yield is proportional to [NaNOZ]”’; this is identical with the previous results found with sodium nitrate. Such a concentration dependence has been explained in terms of a diffusion kinetic model.’ Furthermore, the NO2 yield is unaffected by added acetone, which has been shown to be a good electron scavenger in irradiated ice.2 All of these results are in accord with reaction of HzO+ as in reaction 2; this is a direct analogy of reaction 1. I t would seem that most of the NOz was stabilized as formed. No evidence for NO was seen in irradiated
HzOf (1) (2)
+ NO,-
+ NO2
(2)
L. Kevan, J . Phye. Chem., 68, 2590 (1964). L. Kevan, P. N. Moorthy, and J. J. Weiss, J. A m . Chem. SOC.,
86, 771 (1964).
