J . Phys. Chem.
im,84, 1063-1064
Zn2+ions occupy I sites and two K+ ions occupy I1 sites. As one of three I1 sites is vacant, the adsorption of large nonpolar molecules is possible, and the selective adsorption of PH3 from SiH4 becomes impossible. Zn6-A must have higher catalytic activity than those of less completely exchanged samples since the sixth Zn2+ion at site I1 contacts thoroughly with reactant molecules, as known in Ca6-A.4
References and Notes (1) Takaishi, T.; Yatsurugi, Y.; Yusa, A.; Kuratomi, T. J . Chem. Soc.,
Faraday Trans. 11975, 71, 97; J. Electrochem. SOC.1975, 122,
1700. (2) Rhaghavan, N. V.; Seff, K . J . Phys. Chem. 1976, 80, 2133. (3) Yusa, A,; Ohgushi, T.; Takaishi, T. J. Phys. Chem. Solids 1977, 38, 1233. (4) Takaishi, T.; Hattori, H. J . Am. Chem. SOC. 1977, 99, 7731. (5) Firror, R.; Seff, K. J . Am. Chem. SOC.1978, 100, 3091. (6) Ogawa, K.; Nltta, M.; Aomura, K. J . Phys. Chem. 1978, 82, 1655; J . Phys. Chem. 1979, 83, 1235. Masahiro Nltta" Kiyoshi Ogawa Kazuo Aomura
Department of Chemistry Facuty of Engineering Hokkaido University Sapporo 060, Japan Received April 9, 1979
Energetic 36CiAtom Reactions in Llquid and Solid Mixtures of 1,1-Dichloroethaneand o-Dichlorobenzene with Alcohols and Hexafluorobenzene
Sir: Rack et a1.l have recently reported unusually high labeling yields of [ 1281]monoiodotyrosineand ['2sI]diiodotyrosine if diluted frozen aqueous solutions of mono- and diiodotyrosine, respectively, were neutron irradiated. The authors observed that these labeling yields remained essentially constant over a 100-fold concentration range and suggested that the substrate molecules are trapped in empty spaces in the ice lattice. This matrix supposedly provides a most effective cage which could strongly enhance the geminate recombination of the lZsIand the organic radical resulting from the breakup of the molecule following the reaction capture process. In the course of our studies of the reactions of (n,y)produced recoil 3sCl in frozen solutions of 1,l-dichloroethane (1,l-DCE) and o-dichlorobenzene (0-DCB) with methanol, ethanol, and hexafluorobenzene we have observed a similar phenomenon.2 In these solid mixtures the yields of the 3RC1-labeledparent compounds remain constant over B wide concentration range and are basically identical with those obtained in the neat parent compound if it is neutron irradiated in the solid state. Quartz ampules containing 0.200-mL samples of the mixtures were irradiated in a pneumatic tube of the W R - S reactor of the Central Research Institute for Physics (Budapest) for 3-6 s, at a thermal neutron flux of 1013 neutrons cm-2 s-l and a y dose of less than lo4 rd. Solid samples were irradiated at liquid nitrogen temperature and kept frozen until being processed. The organic and inorganic fractions were separated by extraction as described elsewhere.2a The subsequent identification of the individual organic products was performed by gas chromatography with the method developed by StBcklin and T ~ r n a u .Glass ~ columns 4 m long, 4 mm i.d. packed with 15% squalane on Chromosorb P-AW were used for the analysis of 1,l-DCE mixtures, while for all the other systems columns, 2 m long, packed with 20% SF-96 + 690 0022-3654/80/2084-1063$01 .OO/O
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TABLE I: Radiochemical Yields of 38C1-LabeledParent Compounds 1,l-Dichloroethane and o-Dichlorobenzene with Alcohols and Hexafluorobenzene radiochemical yield, % total activitv system (mole ratio) liquid glassy crystalline 1,l-DCE (neat) 1,l-DCE-EtOH ( 9 : l ) 1,l-DCE-EtOH (6:4) 1,1-DCE-EtOH ( 1 : 9 ) l,l-DCE-C,F, ( 1 : l ) l,l-DCE-C,F, (1:9) o-DCB (neat) o-DCB-MeOH (1:9) 0-DCB-EtOH (1:9)
9.7 i 5.4 + 2.8 f 0.5 rt 3.0 f 2.6 rt 28.9 rt 1.9 rt 1.2 f
0.3 0.1 0.1 0.1 0.4 0.6 0.8 0.1 0.1
5.0 f 0.3 0.8 f 0.1
1.7 f 0.1 1.1 f 0.1
13.1 f 0.1 12.7 f 1.1 11.3 f 0.6 11,6 f 12.5 f 11,l -I: 11,2 f 9.2 f
0.9 1.0 0.5 0.7 0.4
Bentone-34 on Chromosorb W-AW DMCS were applied. Data presented in Table I show the radiochemical yields of the labeled parent compounds in 1,l-DCE and o-DCB as well as in their mixtures with MeOH, EtOH, and C6F6 in the liquid and solid state. While the yield of %C1labeled 1,l-DCE is decreasing with increasing dilution of the parent compound with EtOH or C6F6in the liquid mixtures, it does not change significantly in the crystalline samples. The same is true for the mixtures of o-DCB with MeOH and EtOH. It can also be seen that the nearly constant values of the parent compound yields are characteristic only for the crystalline phase, while the solid glassy systems in this respect behave more or less similarly to the liquid ones. We prefer to interpret our results by assuming that in the frozen (organic) solutions a partial separation of the components of the mixtures occurred. This leads to a formation of clusters of DCE or o-DCB molecules in the frozen solvent matrix. Recoil %C1formed in such a cluster will most likely react with other substrate molecules before it has a chance to leave the cluster. Its reactions will therefore be the same as those of recoil 38c1 in a neat (solid) substrate environment, which is consistent with the almost identical organic yield distribution observed under these conditions as is also demonstrated by data in Table I1 for some crystalline mixtures in comparison with glassy and liquid ones. In order to provide additional evidence for this assumption we carried out some experiments with liquid and frozen (crystalline) samples of C6F6 containing small amounts of C C 4under experimental conditions identical with those described above. As it can be seen from the data listed in Table III in liquid mixtures the yield of the labeled parent compound, CC1338C1,represents only a small fraction of the total radioactivity consistent with the low concentration of CC14 in these systems, while about 16% of the 38Clactivity is stabilized in form of C6F:%1. This latter result is in excellent agreement with the fact that several authors* have found the replacement of fluorine atoms in liquid aromatic systems by recoil 38Clto be a hot process with characteristic radiochemicalyield of 2.6-3.1% per F atom. In the crystalline phase, however, the yield of 38C1-for-F replacement is practically zero, while about 60% of the total activity is stabilized in form of the parent compound, approximately the same amount as in the neat crystalline CC14.6 These results seem to confirm our contention that the substrate molecules (CCl,) are forming clusters (or microcrystals) in these frozen solutions and that the reactions of the recoil 38C1are restricted to an interaction with the substrate molecules contained in the same cluster aggregate. This is in sharp contrast to the reactions of recoil particles in the glassy or liquid state where the substrate 0 1980 American Chemical Society
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J. Phys, Chem. 1980, 84, 1064-1064
TABLE 11: Distribution of the Identified 38Cl-LabeledOrganic Products (except Parent) in Frozen Mixtures of 1:1-Dichloroethane with Hexafluorobenzene a n d Ethanola radiochemical yield, % total activity
__ organic
I J - D C E ~ (neat) l,l-DCE-C,FGb 1:l l,l-DCE-C,F,b 1 : 9 l,l-DCE-EtOHb 9:1 1,l-DCE-EtOHb 6:4 1,l-DCE-EtOH‘ 6:4 l,l-DCE-EtOHd 6:4
52.4 k 4.3 46.8 i 3.8 48.6 i 4.1 45.0 i 0.9 43.7 i 3.6 13.1 i 0.3 7.4 i 0.7
a
Reference 2b.
Crystalline.
l,l,l-
1,2C,H,C138C1
-system (mole ratio)
3.6 3.0 2.7 3.2 2.3
