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Table IaPb : Experimental and Computed Areas of the Fringe Deviation Graphs
S-I: 0
011
Qexptl
X IO4
&csled
x
HzO; 1 = LiC1; 2
= KC1 0.20) (01 = 0.4358; & = 0.3830) 0.0008 0.1002 0.8303 0.8309 0.9999 0.00 10.01 36.31 36.00 31.01 0.32 9.89 35.60 35.59 31.93
(ci = 0.25; lo4
=
=
S-11: 0 = H,O; 1 = LiC1; 2 (E1 =
a1 Qexptl &oalod
x x
104 io4
S-IIIA: 0 a1 Qerptl Qoaiod
=
HzO; 1 = raffinose; 2
S-IIIB: 0 = HZO; 1 011
Qexpti
X lo4
Qosiod
X IO4
KC1
raffinose; 2 = KCl = 0.6122; 02 = 0.3892) 0,0040 1,0002 1,0247 -1.57 21.28 -2.63 -0.83 19.78 -1.19
0.0003 -6.85 - 7.52
S-IV: 0 = HzO; 1
=
raffinose; 2
= 02
X lo4 X IO4
0.0010 1.16 1.04
=
0.0233 23.97 24.10
urea = 0.7383) 1 ,0004 1.0198 7.71 -4.90 7.26 -4.47
a The mean solute concentrations for systems I and I1 are in moles/l., Cr, and the mean solute concentrations for systems IIIA, IIIB, and IV are in g./100 ml., CI. b The partial specific volumes are expressed in ml./g.
Table IT" : Recalculated Diffusion Coefficients (Dlj)"
for the Volume Frame of Referenceb
s-I"
s-I1 S-IIIA S-IIIB S-IV
1.1309 (1.145) 1.1048 (1.069) 0,4303 (0.4303) 0.4300 (0.4309) 0.4206 (0.4210)
Irradiation Effects in the Platinum-Catalyzed Deuterium Exchange of Water with Benzene and Other Substances'
by W. G. Brown, J. L. GarnettrZ and 0. W. VanHook Chemistry Division, Argonne Xutional Laboratory, Argonne, Illinois (Received M a y 25, 1964)
(81
(CI = 0.75; B = 3.00) (01 = 0.6122; 011
Qosiod
=
0.3150) 0.9997 12.50 11.98
(CI = 0.75; 4 = 0.75) ( 0 ~= 0.6122; 02 = 0.3716) -0.0005 0.0027 1,0001 1.0057 2.14 x 104 -4.60 5.46 0.48 x 10' -4.12 1.66 5.46 0.48 (CI = 0.75; Cz = 3.73)
Qeapti
(11) P. J. Dunlop and 1,. J. Gosting, J . P h y s . Chem., 63, 86 (1959).
NaCl
=
cz
0.25; = 0.20) (01 =.0.4370; 0z 0.0002 0.2654 0.6995 -4.43 0.00 8.03 -5.23 0.90 8.45
Using the coefficients in these equations and an expressionll derived in a previous publication, partial specific volumes, b r , for the solute components in each of the five systems were computed. These values, together with the corresponding solute concentrations, are listed in Table I.
-0.0017 (-0.007) 0.0985 (0.141) 0.0023 (0.0022) 0.0056 (0.0066) 0.0000 (0.0000)
a All diffusion coefficients have units of see.+. See ref. 10. c The data for the first two systems are for concentrations expressed in moles/l.; the data for last two systems are for concentrations expressed in g./100 ml. It should be noted that bhe values of the cross-term diffusion coefficients depend on the concentration scale used.
The Journal of Physical Chemistry
I n the process of initiating deuterium exchange between water and an organic material, e.g., benzene, by heating with platinum oxide, recently reported3 and described as "self-activation," the hydrogen required for the generation of active sites must be supplied by C-H dissociative mechanisms. It could be anticipated, therefore, that the activation process, and hence the scope of this technique for isotopic labeling, might be extended by ionizing radiation whether supplied 'externally, perhaps by y-irradiation, or internally as in the production of tritium-labeled materials. With the deuterium oxide-benzene-platinum oxide as a test system of good reproducibility, an accelerating effect of exposure t o y-rays prior to heating is actually found. Prior irradiation with ultraviolet light is also effective in facilitating activation of the catalyst and this finding has practical as well as theoretical interest. Preliminary experiments indicate, for example, that photoactivation will initiate deuterium exchange in pyridine, a substance otherwise immune to exchange by the "selfactivation'' technique. Reaction mixtures, consisting typically of 1.7 g. of benzene, 1.6 g. of deuterium oxide, and 0.02 g. of platinum oxide, were outgassed, sealed in appropriate ampoules, irradiated, and heated as shown in Tables I and 11. The products analyzed by low-voltage mass spectrometry. (1) Based on work performed under the auspices of the U. S. Atomic Energy Commission. (2) School of Chemistry, University of New South Wales, Kensington, N. S. W., Australia. (3) J. L. Garnett and W. A. Sollich, J . Phys. Chem., 68, 436 (1964).
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3065
Table I : Exchange of Deuterium between Benzene and Deuterium Oxide under “Self-Activation” Conditions Time, hr.
Temp.
114
a
dQ
12 99.7 16 99.6 21 97.6 24 94.7 41 86.9 51 71.0 66 23.9 0.5 100 1.5 99.7 2.5 99.0 Equil., calcd.a 1.56
134
dl
dl
Isotope distribution------------------ds
0.30 0.40 0.90 1.30 2.20 7.30 23.3
0.03 0.40 0.50 1.30 2.40 15.3
0.03 0.20 0.50 1.00 2.20 10.6
0.09 31.2
~
da
da
0.03 0.20 0.50 1.40 3.50 10.7
0.03 0.20 0.80 2.00 6.30 10.4
0.05 0.40 1.60 5.30 7.20 5.90
0.09 23.5
0.09 9.37
0.09 1..56
d4
... 0.30 0.27 9.37
t . .
0.09 23.5
Calculated statistical distribution of deuterium a t exchange equilibrium.
Table I1 : Effect of Radiation on Catalyst Activity in the Exchange of Benzene with Deuterium Oxide -Heating
c_____Irra&ationa Source
High pressure arc C
Low pressure arc d e
f
Exposure
0.1 10 3 1 1
Mrad Mrads Rfrads hr. hr. 1 hr. 1 hr. 0.25 hr. 1 hr. 1 hr. 1 hr. I hr.
Temp., ‘C.
134 134 114 134 114 i:i4 134 17~4 1114 11.4 114 1114
periodTime, hr.
1.5 2.5 21.7 2.5 21.7 21.7 1.5 21.7 21.7 21.7 21.7 21.7
Isotope distribution*-----da
do
dl
d2
99.7 67.5 93.6 91.0 5’7.4 77.7 80.6 80.4 15.8 28.0 96.9 29.2
0.20 18.7 2.64 3.50 16.9 14.5 12.6 9.70 20.6 26.0 2.10 25.4
0.04 6.40 0.86 0.90 7.40 3.80 3.30 2.60 18.7 16.0 0.40 16.0
0.02 3.11 0.50 0.60 5.70 1.64 1.40 1.70 15.5 10.0 0.18 11.2
-
ds
0.01 1.70 0.46 0.60 7.20 0 93 0.76 1.50 16.1 7.50 0.11 8.90
d6
0.01 1.55 0.68 1.20 2.90 0.76 0.67 1.90 9.50 6.50 0.09 6.40
0.02 1.13 1.23 2.40 2.60 0.80 0.71 2.20 3.80 4.00 0.18 3.00
a Cobalt-60 ?-ray exposures in Mrads a t a dose rate of 4 X I O 6 rads (room temperature). Low pressure arc exposures made at a distance of 40 mm. from a coiled mercury arc (Nester-Faust UY-300). High pressure arc exposures with sample, forced air-cooled, a t 60 mm. from a high pressure arc (Engelhard Industries 6738-36). Benzene-deuterium oxide ratio such as to provide a statistical deuterium distribution 55: 45. c Benzene-deuterium oxide mixture irradiated; platinum oxide introduced subsequently. d T’ycor ampoule, all others quartz. Benzene-platinum oxide mixture irradiated; deuterium oxide introduced subsequently. Deuterium oxide-platinum oxide irradiated, benzene introduced subsequently.
Apart from any radiation effects, the rate of deuterium exchange with benzene and the distribution of deuterated species may vary with the degree of agitation and the particular batch of platinum oxide. Under the conditions employed, and with all experiment,s done on one lot of platinum oxide, the behavior is reproducible and the oneet of exchange under self-activation after a period of incubation, approximately 12 hr. a t 114” or a much shorter tiine at 134O, can be seen clearly in the data of Table 1. These results illustrate quite strikingly, in tlhe early buildup of highly deuterated species, the relative importance of sites favorable for multiple e ~ c h a n g e , ~in this mode of activation. The accelerating effect of preirradiatioii
appears in the data of Table I1 relating to experiments under conditions identical otherwise with those pertaining to Table I. Since benzene absorbs strongly in the wave length region most effective in photoactivation, it is a plausible postulate that a photochemical product derived from benzene is an active reducing agent for platinum oxide. However, irradiation of a benzene-platiiium oxide mixture t o which deuterium oxide is added subsequently does not produce an appreciable effect. But the ir(4) (a) J. I,. Garnett and W. A. Sollich, J . Catalysis, 2, 350 (19G3); (b) i b i d . , 2, 339 (1963). ( 5 ) J.
R.Anderson and C. Kernball, A d a m . Catalysis, 9, 51 (1957).
Volume 68, Number IO
October, 196s
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radiation of a deuterium oxide-platinum oxide mixture, with subsequent addition of benzene. is effective, and so also is the irradiation of a benzene-deuterium oxide mixture with subsequent addition of platinum oxide. The acceleration due to irradiation is not simulated by hydrogen peroxide which, added in concentrations up to 3 X M , has very little effect. It appears therefore that photocheniical excitation in platinum oxide and a resultant interaction with water niay be involved in the generation of active centers that grow or multiply during the subsequent heat incubation. The photochemical activation is reniinisceiit of the photochemical reduction of zinc oxidc6 and of mercuric sulfide' in aqueous suspensions. Cyclohexane responded poorly to the self-activation exchange technique with deuterium uptake to the extent of O.lY0 after 68 hr. at 134"; prior exposure under the low pressure mercury lamp brought about a modest twofold increase iii deuterium content. Exposure of a niixture containing pyridine, deuterium oxide, and platinum oxide to the low pressure source for 1 hr., followed by heating to 134" for 17 hr., effected deuteration to the extent of 0.8%; without the ultraviolet exposure and heated for 60 hr. a t 134' there was no detectable exchange. The distribution of label in the benzene, cyclohexane, and pyridine, deuterated on irradiation-activated catalyst, indicates concurrent multiple ant3 stepwise exchange. There is an indication, to be tested iii future studies, that with benzene a t least, ultraviolet irradiation is soniewl-iat more effective in activating sites on which stepwise exchange occurs. ~~
~
(6) J G . Calvert, K. Theurer, G T. J . A m Chem Soc , 7 6 , 2675 (1954).
Rankin, and Vi,Sf SfacXevin,
(7) L. I. Grosswemer, J . Phhys Chem , 59, 742 (1S.55)
Electron Spin Resonance Studies of Radical Reactions in Irradiated Alkyl Halides a t
Low Temperatures
by P. B. Ayscough and H. E. Evans'
a simple recombination or disproportionation reaction. There are, however, a few examples of systems in which the occurrence of secoiidary reactions is indicated by chainges in the hyperfine structure of the e.s.r. spectra. For instance. the addition of phenyl radicals to olefins a t - 196' has been observed by Bennett and Thomas,2 while the isomerization of n-propyl, n-butyl, and isobutyl radicals a t - 196' has been reported by Ayscough and Thomson Attempts to extend the observations on n-propyl and n-butyl radicals to higher temperatures ( - 180 to - lL500)were largely unsuccessful because the rate of disappearance of the radicals increases so much that the change from a six-line t o an eight-line spectrum (corresponding to the formation of isopropyl or sec-butyl radicals) cannot be followed readily. Furthermore, the asymmetry of the spectra, suggesting the presence of another radical, possibly halogenated, becomes more pronounced as the temperature increases. I t was therefore decided to confine further studies of isomerization reactions to irradiated isobutyl halides in which these problems are much less serious.
Experimental Commercial samples of alkyl halides were dried over calcium chloride, distilled through a 20-em. column packed with Fenske helices, exhaustively degassed (
