3202
I\OTES
compounds 1 and 2 is generally less temperature dependent than are the individual 6, the uncertainties involved in comparing data derived from different critical solution temperatures with data for 25" are minimized.
Chemical Species Containing Pa2and Sa5 Subsequent to the Neutron Irradiation
of Thiourea1
by Cleon C. Arrington and Robert W. Kiser ~~~
~
~
~
~
Table I: Comparison of Critical Solution Temperatures and Solubility Paremetere for Solutions of C7F16 and C,FlsH Mixture
T 0 , ' K . 8~
- 8~
IH
IH*
Ref.
8.5 8.7 9.0 9.2 8.9 9.2 9.2 9.2
7.4 8.2 9.2 10.Ob 7.4 8.2 9.2 10.Ob
a Thiswork a Thiswork
Department of Chemistry, Kansas State university, Manhattan, Kansas 66604 (Received April .W91966)
The chemistry of recoiling atoms following bombardment with heavy nucleons has been investigated in some depth. However, a detailed understanding of the nature of the products to be expected from the neutron irradiation of a given substance and satisfactory 1 This work explanations of the mod@ of formation of all of the 1 products are yet to be realized. In an early study, This work Whitmore2 investigated the production of phosphorusJ. H. Hildebrand, B. B. Fisher, and H. A. Benesi, J . Am. 32 from sulfur-32 in the neutron irradiation of thioprea; Chem. SOC.,72, 4348 (1950). * From solubility in nonpolar he reported the chemical oxidation state of the phossolvents. phorus-32 produced and discussed a possible mode for its formation. There have been no further studies of the neutron irradiation of thiourea since Whitmore's For both C7Hl6 and c-CaHl2, the change in ( 6 ~- ),6 investigation and a brief report by Adams and Campin going from C7F16 to C7F15H is practically negligible. bell. For benzene, on the other hand, the value of ( 6 ~- 8 ~ ) The purpose of this note is to present the results of is 0.33 unit lower in C~FISH than in C7Fl6 and for dioxane an investigation of the labeled products formed upon the difference is 0.46 unit. We interpret these changes neutron irradiation of thiourea, the nature of the as indicating that the interactions of C7Fl6 and C'IF~SH species resulting from the recoil and radiation damage with heptane and cyclohexane are virtually the same effects, and the relative quantities for both sulfur-35 but that in benzene there is a considerable contribution and phosphorus-32 in these species. to the solution behavior from interactions between the Experimental CH group and the a-electrons of the benzene molecule, Sample Irradiation. Thiourea (Matheson Coleman the indications of which are suppressed in the comand Bell, reagent grade) was recrystallized three times parison of 6a with a ~ * . In dioxane, the interaction befrom ethanol and dried for 24 hr. over sulfuric acid. tween the oxygens and the CH group of the CTFxH is Two 5.0-g. samples were irradiated in air in the ORNL sufficiently strong to show even in the comparison graphite pile. Pertinent data concerning the irradiaof ,6 and 6=*. The same conclusions are suggested by tions are: thermal neutron flux, 5 X 10'l cm.-2 set.-'; the direct comparison of the To values. For both irradiation time, 3 days; pray ffux, 7 X lo6 r./hr.; mixtures is n-heptane and cyclohexane, To for C~FISH sample temperature, -50". about 20" lower than for c7F16 mixtures. For benzene, Counting Procedures. Total activity measurements the difference is 73" and for dioxane it is 123". The for Pa2-and Sa5-containingsamples were made using a interactions suggested by this comparison have been Packard Tri-Carb liquid scintillation spectrometer revealed in n.m.r. spectroscopy in solutions of both and PPO-POPOP-naphthalene-dioxane scintillator soCHC139and C7FI5H1Oin benzene. The heats of mixingll l u t i o n ~ . ~A Geiger-Miiller "dip counter" tube (window of C7FI5H with dioxane are also consistent with the formation of hydrogen bonds between dioxane and (1) This work wm supported by the U. 8. Atomic Energy CommisC,FuH. sion under Contract No. At(l1-1)-751 with Kansas State University. 323 350 387 431 305 331 314 308
2.62 2.88 3.20 3.32 2.58 2.86 2.87 2.86
~
(9) W. G. Schneider, J . Phys. C h m . , 66, 2653 (1962). (10) D. L. Anderson, R. A. Smith, 8. K. Alley, A. G. Williamson, D. B. Myers, and R. L. Scott, ibid., 66, 621 (1962). (11) R. J. Knight and A. G. Williamson, unpublished results.
The. Journal of Phy&
(%-?niStry
~~~~~~~
It is a portion of a Dissertation presented by C. C. Arrington to the Graduate School of Kansas State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry. (2) F. E. Whitmore, Nature, 164, 240 (1949). (3) A. Adams and I. G. Campbell, Trana. Faraday SOC.,59, 2001 (1963).
NOTES
thickness -30 mg./cm.2) and a Borg-Warner scaler also were used to determine the total Ps2activities. The counter was regularly standardized with aqueous solutions of Pazstandard (as HsPa204). With the Packard Tri-Carb liquid scintillation spectrometer, the Ss6 and the Pa2activities were determined in separate counting channels. With 620 v. on the photomultiplier tubes only the Pa2activity was counted. With 920 v. on the photomultiplier tubes, both the Pa2 and the 5% activities were counted. The count rates at the higher voltage were corrected appropriately to yield the Sas activities. The small amounts of C14 and Paaproduced in the irradiation (less than l%,of the Ss5 produced) were neglected. The average of all determinations for the two samples gave 388 f 16 pcuries of Pa2and 77.8 i 1.5 pcuries of produced. The error limit represents one standard deviation. Analytical Methods. Paper electrophoretic techniques similar to those employed by Lindner and Harbottles and Grassini and Lederefl were used in the chemical separations of the ionic species. I n the analyses 0.1 N NaOH electrolyte was used with a commercial paper electrophoresis apparatus and a constant potential gradient of 33 v./cm. With three parallel 1 X 12 in. Whatman 3 MM chromatography paper strips, currents were less than 25 ma. Samples of 20-100 X per strip were analyzed for 2.5 hr. The strips were dried at 25” and cut into 0.40.5-in. sections. Each section was placed into separate scintillation solutions and counted. No carriers were employed in these experiments. The mobilities of species containing the Ps2and the 5%activities were compared to the mobilities of authentic samples. Radiolabeled Pod8- and Sod2- standard samples were used to establish the ionic mobilities. The ionic mobility of S2- was determined from a bmic S2- solution and development of the strip with a Pb(OAc)2 solution, Electrophoretic analysis of the irradiated samples indicated that essentially all of the sulfur-35 was contained in ionic species. Theoretical considerations indicated that the parent thiourea molecule should be labeled at least in part. It was found that in basic solutions, the thiourea hydrolyzed to yield S2-. Therefore the amount of labeled thiourea present was determined by reverse isotope dilution and recrystallization to constant specific activity. The values obtained by this technique compared well with values determined from 9-xanthenol derivatives.’
Results and Discussion The electrophoresis of the irradiated samples indi-
3203
cated the activity to be principally in the form of S2and S012- (67 and 29%, respectively). A portion of the S2- activity determined was found to be due t o the hydrolysis of labeled thiourea. From the reverse isotope dilution experiments, thiourea was found to contain 31% of the total sulfur-35 produced. By difference, S2- contained 36% of the total sulfur-35 formed. About 4% of the Ss5 activity was found t o remain at the origin of the electrophoresis strip. The lack of mobility of this labeled species leads us to the conclusion that it is probably covalent in nature. We cannot satisfactorily explain the lack of oxidation of the Sas produced. It is possible that the double bond to the sulfur atom makes the bond less susceptible to rupture during recoil of the Sa atom. This would lead to a higher percentage of the Ss5being found in the thiourea molecule and as S2-. The S%-containing species, as determined, accounted for all of the Sa6 produced in the sample. The Pa2species found to remain on the strip accounted for only 57% of the total Pa2produced in the sample and was found to be distributed among hypophosphate (61%) and phosphate (39%). The hypophosphate ion or its precursor was found to be oxidized to phosphate upon storage of the sample at room temperature during the analyses. This phenomenon also has been observed t o occur in inorganic ~ a l t s . ~ ~ ~ ~ ~ Adams and Campbell3 have investigated the effect of oxygen in the lattice upon the final oxidation state of the recoiling P32atom and concluded that in matrices in which the molecule itself does not contain oxygen and where oxygen is carefully excluded, the Pa2can be expected to be in a f 5 oxidation state. Where oxygen is present, the percentage of labeled $3 oxyaniom increases significantly. Oxygen is considered to act as a scavenger, stabilizing the recoil species in a state which leads to +3 oxyanions upon dissociation of the sample. Since the samples reported in this study were irradiated in air, it is concluded that the presence of oxygen had such an effect and therefore a significant portion of the activity (43%) was incorporated in +3 oxyanions of phorphorus. The data indicate that, in the recoil processes for both the sulfur-35 and phosphorus-32, most of the (4) T.W.Lapp and R. W. Kiser, J. Phys. Chem., 66, 152 (1962). (5) L. Lmdner and G. Herbottle in “Chemical Effects of Nuclear Transformations,” Vol. I, International Atomic Energy Agency, Vienna, Austria, 1961, p. 485. (6) G. Grassini and M. Lederer, J . Chromatog., 2, 326 (1959). (7) R. W. Kiser, M. D. Shetlar, and G. D. Johnson, Anal. Chem., 33, 314 (1961). (8) R.F. C. Cleridge and A. G. Meddock, Trans. Faraday Soc., 59, 936 (1963).
Volunts 69,Number 0 September 1966
NOTES
3204
2.4
bonds to these atoms are broken (the recoil energy of Patis of the order of 200 kev.) and that, subsequent to the themahation of these atoms (little ionhation is expected), the resulting species are either oxidized or reduced by their immediate surroundings to form matrix-stabikd precursors of the observed products.
I
I
2.0 nCCHJ
TI (Sec.)
1.6-
Measurement of the Spin-Lattice Relaxation Times of Dimethyloctylamine Oxide through
1.2-
the Critical Micelle Concentration I
,
by Kenneth D. Lawson and Thomas J. Flautt Ths Procter & &mbk Company, Miami VauSy Laboratories, Cin&nn&i, Ohw &%S9 (Received May S,1986)
Figure 1. Spin-lattice relaxation times of DCAO aa a function of concentration.
The nuclear spin-lattice relaxation times (TI) of the various proton moieties of the nonionic surfactant dimethyloctylamine oxide [CHa (CHZ)7N(0)(CHa)2 1 (DCAO) have been determined. The measurements were made on oxygen-free solutions of DCAO in DzO at 32”. A Varian Associates Model A-60 spectrometer was used and the TI values were determined by the progressive saturation meth0d.l A “doped” water sample with a known relaxation time was used to calibrate the instrument. The preparation of the surfactant has been described elsewhere.2 The experimental TI values are shown in Figure 1 as a function of the concentration of DCAO in moles per liter. There was no indication that there is more than one TI for a band of a given chemical shift. However, the method used to determine the relaxation times would indicate multiple T1values only if a substantial distribution were present. All of the TI values show an apparent maximum near the critical micelle concentration (c.m.c.) of the surfactant.* The magnitudes of < T ~ , N c
