2497
W4(n,p)C14HOTATOMCHEMISTRY OF CARBON
Table I11 : Comparison of the Ratio of Deactivating Efficiency of COZt o SF, for Different Systems
-----
Species deactivated-1,l-
DimethylButyl cycloradicals propane 8ec-
Efficiency C02/SFe Temp., "C. Reference
01
NzOs
1.0
0.89
0.70
0.40
0.20
27" a
50" b
27"
459" d
100" This work
C
Ethane
a J. E. Morgan and IT. I. Schiff, J . Chem. Phys., 38, 1495 D. J. Wilson and H. S. Johnston, J . Am. Chem. Soc., (1963). G. M. Kohlmaier and B. S. Rabinovitch, 75, 5763 (1953). J. Chem. Phys., 38, 1709 (1963). M. C. Flowers and H. M. Frey, J. Chem. Soc., 1157 (1962).
shown in Table 111. There are wide variations in temperature but these are ,unlikely to cause large
changes in the figures quoted. It is evident that deactivation efficiencies vary with the species deactivated and any theory purporting to justify third body efficiencies should be tested in a variety of systems. Since relative deactivating efficiencies vary strongly according to the species being deactivated, it may be that acetone is not always a more efficient third body than azomethane. Unfortunately, for this purpose, both molecules are highly reactive; and it seems unlikely that a study of their relative efficiences for a variety of different systems would be feasible. Finally, it may be noted that the relative inefficiency of azomethane makes the third body region occur a t relatively high pressures. This makes the photolysis of azomethane a convenient system in which to study third body effects.
Acknowledgment. We wish to thank the National Science Foundation for its support of this work.
The N14(n,p)C1*Hot Atom Chemistry of Carbon in Hydrazine Sulfate
by John D. Vaughan and Van T.Lieu Departments of Chemistry of The University of Hawaii, Honolulu 1.4, Hawaii, an% Virginia Polytechnic InsttitUte, Blacksburg, Virginia (Received March 1.4, 1964)
Chemical separations have been made of the radiocarbon activities produced when pile neutron-irradiated hydrazine sulfate crystals are dissolved in water. A wide variety of labeled one-carbon compounds was found. Cyanamide, methylamine, and guanidine were formed in the largest amounts; other radio compounds found are carbon dioxide, carbon monoxide, formic acid, formaldehyde, urea, methylhydrazine, and three species that have the properties of cyanic acid, methylenediamine, and formamidine. Paths leading to these products are suggested.
The nuclear reactions N14(n,p)C14and N14(p,cr)Ci1 provide radioactive carbon atoms with recoil energies of some thousands of electron volts. The recoiling atoms may enter chemical combination with atoms or ions of bhe eiivironnient after dissipating most of the recoil energy. YfLnlcwich and co-workers'-8 showed that a wide variety of labeled one-carbon compounds
is produced when ammonium salts are irradiated with thermal neutrons and subsequently dissolved in water. (1) P. E. Yankwich and J. D. Vaughan, J . A m . Chem. SOC.,76, 5851 (1954). (2) P.E.Yankwich and W. R. Cornman, ibid., 77,2096 (1955). (3) P. S. Marteney, Thesis, University of Illinois, 1961.
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September, 196.4
2498
Dissolution of the targets in water introduced the possibility of secondary reactions between crystal-stabilized recoil products and water to produce the final observed products. In contrast to the results of Yankwich and co-workers, Yang and Wolf4 and Cacace and Wolf5 found essentially only labeled methane and methylamine produced by the nuclear reactions S I 4 (n,p)C14and N14(p,a)C11in gaseous NH3 targets; the targets were not dissolved in water prior to analysis. Cacace and Wolf5 observed that the fraction of Clllabeled CH4 grew a t the expense of labeled CH3NHz with increasing dose of protons; this growth was attributed to the increasing radiolysis of the target during the irradiation with protons. I n this paper, we report 'research on neutron-irradiated hydrazine sulfate, the first of a series of targets of hydrazine and salts of hydrazine. This research is intended as an extension of the prior investigations of Yankwich and co-workers and Wolf and co-workers upon salts of ammonia and ammonia targets.
Experimental Sample Preparation and Irradiation. Five grains of reagent grade hydrazine sulfate was placed in a necked quartz ampoule and dried for 2 hr. a t 110'; the anipoule was then attached to a vacuum line and held under vacuum for 2 days. After this, the system was flushed with helium and pumped down to a few microns to exclude atmospheric oxygen, and the quartz ampoule was sealed under a helium atmosphere (with slightly positive pressure) with an oxygen-hydrogen flame. The specimen was irradiated in the Oak Ridge National Laboratory graphite reactor for 576 hr. in a neutron flux of -5 X 1011 n. set.-' and a yflux of -5 x 105 r. hr.-I at an ambient temperature not exceeding 40'. The specinieii was given 13 inonths to cool off. The ampoule was opened in a drybox and stored in a desiccator between experiments. Preliminary Experiments. Prior to determination of the detailed distribution of C14 among the various possible one-carbon compounds, the gross distribution of the carbon radioactivity over total gaseous (TG), total nongaseous (TNG), total basic fraction (TB), and total noiibasic fraction (TKB) was determined. the following carriers were introduced into a dissolved sample of the target (ca. 0.05 to 0.10 g. of NzH6S04): COz, CO, CH4, CH3?;Hz, HCOOH, HCHO, and CH30H. The procedure used to separate these carriers into the indicated fractions was essentially that of Yankwich and Vaughan,l except that CO was oxidized over CuO at 315' instead of "Hopcalite" at rooin temperature. All fractions were converted to BaC031s2 prior to counting. The Journal of Physical Chemistry
JOHN D. VAUGHAN A N D VANT. LIEU
Separation of Individual Carriers. Specific chemical reactions and derivative formations were used to isolate carbon radioactivity in the corresponding carrier fractions. In most cases, several carriers were added to the dissolved target sample and separated; in general, the solution of target sample and carriers was made up to 100.00 ml. and aliquots taken for individual separations. Carbon Dioxide, Carbon Monoxide, Methane, Formic Acid, Formaldehyde, Methanol, Methylhydraxine, Cyanamide, [:rea, and Guanidine. The procedures given by Yankwjch and co-workers1,216 were used. Methylamine. The N,N'-Methylphenylthiourea derivative'~~was prepared and recrystallized from ethanol. Hydrogen Cyanide. Direct precipitation of AgCN may lead to anomalously high results, due to adsorption of carrier-free carbon radioactivity onto the pre~ i p i t a t e . ~To reduce this effect, HCN was distilled from the original solution of the carriers and the target sample under low heat into dilute NaOH. A stream of air passing through the distillation flask and receiver flask facilitated the distillation. The pH of the receiver solution was adjusted to a value of 6, and AgSO3 was added to precipitate AgCN. AgCX was oxidized to carbonate in boiling alkaline permanganate. Carrier-Free Activity. The separation and counting of the above carriers accounted for only 84% of the total activity (see Tables I and 11). The remaining 16% of the activity was separable into three parts, revealing properties consistent with cyanic acid, meth~lenediamine,~ and formamidinel6respectively. Cyanic Acid. HOCN (or OCNH) undergoes hydrolysis in strong acid to COZ.'O An acidified degassed solution (CO?, CO, and CHI collected previously) was distilled to near dryness into a receiver containing dilute NaOH. The receiver was acidified, and the liberated COz was collected in a bubbler containing NaOH. An air sweep with a measured quantity of COZ served as a carrier during the distillation. Methylenediamine and Formamidine. When HCOOH and HCHO were made alkaline (pH 10) and allowed to stand 10 hr. before these carriers were isolated (4) J. Y. Yang and A. P. Wolf, J . Am. Chem. SOC.,8 2 , 4488 (1960).
(5) F. Cacace and A. P. Wolf, (bid., 84, 3202 (1962). (6) P. E. Yankwich and W. R. Cornman, ibid., 78, 1560 (1956). (7) T . W. Lapp and R. W. Kiser, J . Phys. Chem.. 66, 152 (1962). (8) R. L. Shriner, R. C. Fuson, and D. Y. Curtin, "The Systematic Identification of Organic Compounds," 4th Ed., John W'iley and Sons, Inc., New York, N. Y., p. 202 ff. (9) J. D. Vaughan, Thesis, University of Illinois, 1954. (10) F. C. Whitmore, "Organic Chemistry," 6th Ed., D. Van Nostrand Co.. Inc., Princeton, h'. J., p. 539.
_1T14(n,p)C14 HOTATQMCHEMISTRY OF CARBON
2499
Table I : Distribution OF Carbon-14 among Various Fractions in Hydrazine Sulfate Number of Beparate determinations
Fractiona
TG TNG Sum TNB TB [HOCN (and/or OCNH)~ Sum
% activity
5 3
9 . 6 f0 . 2 9 1 . 8 Z!= 0 . 8 101.4 1 0 . 8 f0 . 0 76.0 f1.0 5 . 2 i0 . 1
.. 3 2 2
..
91.0
TNG, total nongaseous fraca TG, total gaseous fraction; tion; T S B , total nonbasic fraction; TB, total basic fraction. Hypothesized, carrier-free.
Table I1 : Distribution of Carbon-14 among One-Carbon Compounds in Hydrazine Sulfate and Ammonium Sulfate"
__--_-
N%HeSO&-----
Number of
separate determinations
Compound
,
70activity
(NHdzSOa % activity
coz co
3 6
CHI Sum
6
HCOOH HCK HCHO CHaOH Sum
4 2 4 2
[HOCN (and/or OCNH)]'
2
5 2 f 0 1
2 2 2 4 4 2 3
1 4 . 7 It 0 . 7 12.1 f 0 . 8 3 . 4 f0 . 7
16.1 0.0 7.3
6 . 6 f0 . 6
... ... ...
Over-all sum a
See ref. 2.
4 . 4 Z!= 0 . 0 5.4f0.1 0 . 0 f0 . 2
9.8 5 9 f 0 0 O f 0 4 O f 0 0 5 f 0 10 4
3 0
2 2
4.2 f0 . 3 3 5 . 0 f2 . 2 1 . 4 f0 . 5 77.4 102.8
39.5 2.0 0.5 42.0 15 3 13 0 33
5 9 2 7 4
... 23.4 98.6
Hypothesized, carrier-free.
and counted, their per cent activities were 10.1 -f 0.3 and 10.6 Z!= l.O%, respectively. When these carriers were isolated and counted without a preliminary alkaline treatment, their per cent activities were 5.9 f 0.3 and 4.0 f 0.270, respectively (Table 11). These results are consistent with alkaline hydrolyses of HC-
NH(hTH2) to HCOOH and CH2(XH2), to HCHO This hypothesis is supported by the fact that the activity attributed to HCNH(NH2) and CH2(YH2),remained with the basic fraction (TB) following acid distillation (Tables I and 11). Radioactivity Determinations. The total radiocarbon activity per gram of sample and the radioactivities of the various fractions and carriers were determined by the method of Yankwich and co-workers,1~2~6 except that the COz evolutes from the various BaCO8 specimens were counted in the proportional region in a Bernstein-Ballentine counter'l rather than an ionization chamber. The counter gas consisted of one part CH, and three parts He.12 The per cent activities reported are based upon total recovery, except in cases where less than 100% of the carrier isolate was recovered. In such cases, a specific activity calculation was required.l Results of Analyses. Table I gives the post-solution distribution of carbon radioactivity over the indicated gross fractions for the hydrazine sulfate target. Table 11 gives the breakdown of the distribution of Table I into individual one-carbon compounds; for comparison, the results of Yankwich and Cornman2 for the ammonium sulfate target are also given. The per cent activities given for hydrazine sulfate are based upon a total target activity of 772,800 Z!= 2400 counts min.-l g.-l, the average of two determinations. The uncertainties given are average deviations from the niean. That the over-all sum of the per cent activities is greater than l0OyGis due to the expressed uncertainties in the individual per cent activities as well as to the uncertainty in the total activity. In Table I, we see that the sum of TKB, TB, and HOCN (and/or OCXH) is 91.0%, in reasonable agreement with TKG at 91.8%. Also, the sum of COz, CO, and CH, (Table 11) is 9.8%, which agrees well with TG at 9.6Oj, (Table I). Finally, the sum of the basic compounds (Table 11) is 77.4%, in agreement with T B a t 76.0YG(Table I).
Discussion Adopting the views of Yankwich13 (based upon the model of Seitz and Koehler14) we envision the recoil carbon coming to a halt far from the site of the nuclear event, trapped in a terminal "hot spot" produced by the final 25-50 e.v. of the recoiling atom. This modest (11) Obtained from Atomic Products, Inc., Center *Moriches, Long Island, N. Y. (12) R. L. Wolfgang and F. S. Rowland, Anal. Chem., 30, 903 (1958). (13) P. E. Yankwich, Can. J . Chem., 34, 301 (1956). (14) F. Seitz and J. 5 . Koehler, "Solid State Physics," Vol. 2 , Academic Press Inc., S e w York, X. Y., 1956.
'Volume 68, h'umber 9
September, 1964
JOHN D. VAUGHAN AND VANT. LIEU
2500
energy could produce only limited fragmentation of the complex ions of the target.13 The stopped carbon atom could react in a number of different ways to form different products, depending upon the free radicals or ions present in the hot spot. The probability of formation of a given free radical may depend roughly inversely upon the energy required for its production. Table I11 gives bond energiesl5-l9 pertinent to hy-
Table I11 : Bond Energies (kcal. mole-') N-N N-H S-0 (in SO,+) a
38 f4" 93.4" 80-90'
See ref. 15. 'See ref. 16.
drazine sulfate and ammonium sulfate targets. On this basis, it is likely that N-nT rupture is most probable and that X-H and S-0 ruptures are relatively less probable. Therefore, in the hydrazine sulfate target, the formation of reactive KH3+ ion radicals would probably be the dominant factor in the chemistry of the hot atom. In the ammonium sulfate target, one might expect a roughly balanced competition for the CI4 atom between SH3+, H, S03-', and 0 radicals produced by N-H and S-0 ruptures. The per cent activities given in Table I11 support this conclusion. Thus, in the hydrazine sulfate target, labeled compounds with more than one C-S link (such as guanidine, urea, cyanamide, methylenediamine, and formamidine) could result from consecutive reactions of the recoil atom with XH3+ ions; excess positive charge, where developed, could be lost through proton transfer from the recoil species to sulfate ions. I n the ammonium sulfate target, only a single labeled species, urea, contains more than one C-N link, which may attest to the relatively smaller supply of XH3+ion radicals in the hot spots of that target. In hydrazine sulfate, methylamine may result from combination of the recoil carbon atom with a NH3+ ion, followed by hydrogen atom abstraction from neighbor NzH6+2ions or by direct reaction with hydrogen atoms produced by partial fragmentation of these ions. Carbon nionoxide and carbon dioxide might be the products of reactions between the recoil atom and atomic oxygen produced by partial fragmentation of sulfate ions in the hot spot. Other labeled oxygen-containing species could have obtained oxygen in this way. Alternatively, these species could result from hydrolyses of lattice-activated precursors during disThe Journal of Physical Chemistry
solution of the target sample.' Thus, cyanic acid might be produced by the hydrolysis of a part of the crystal-entrapped cyanamide. Similarly, formic acid, formaldehyde, and urea could be hydrolytic products of formamidine, methylenediamine, and guanidine, respectively. In hydrazine sulfate, labeled compounds containing ?J and H account for 74y0 of the total activity, but those containing 0 and/or H account for only 20y0 of the total activity. In ammonium sulfate, virtually the reverse is true, where labeled N and H species account for 20% of the activity and labeled 0 and/or H 71%. This large yield of oxygen-containing labeled compounds in the ammonium sulfate target points to the powerful scavenging effect of lattice oxygen.2 That scavenging by oxygen is less effective in hydrazine sulfate is probably due to the competitive scavenging by NH3+ions, present in relatively high concentration because of the comparatively small N-N bond energy. Another factor contributing to the reduced scavenging of recoil atoms by lattice oxygen in hydrazine sulfate could be the reaction of hydrazinium ions with the atomic oxygen; the analogous reaction in ammonjum sulfate would be less likely because of the relatively greater stability of NH4f in comparison with NzH4+2 under oxidizing conditions. y- or X-ray radiolysis during the neutron irradiation probably had small effect upon the final fate of the recoil carbon. A simple calculation based upon the radiation dose indicates that the per cent radiolytic decomposition of the target can be expressed by 0.35G, where G is the number of molecules decomposed/100 e.v. of energy absorbed. If G is 5 or less,ao~B1 the per cent decomposition is 2% or less. Since the rates of the reactions of radiolytically produced species and any given recoil atom species are diffusion controlled in crystalline targets6 and therefore very slow, the contri-
(15) L. Pauling, "The Nature of the Chemical Bond," 3rd Ed., Corne11 University Press, Ithaca, N. y . , 1960, p. 85 ff. (16) From enthalpies of formation,'' the bond energy of the sulfuroxygen bond is calculated to he 95 kcal. mole-' for SO2 and 91 kcal. mole-' for 808; the bond length in both SO, and SO8 is 1.43 L.l5 The bond length in SOa-2is 1.49 L.15 If we assume a bond energybond length relation E73 18 or log Er3 19 we estimate the bond energy to be between 80 and 90 kcal. mole-'. of S-0 in (17) G .N. Lewis, M. Randall, K. S. Pitzer, and L. Brewer, "Thermodynamics," McGraw-Hill Book Co., Inc., New York, N. Y., 1961, p. 685. (18) H. Feilchenfeld, J . Phys. Chem., 61, 1133 (1957). (19) N . McKelvie, Third Annual Metropolitan Regional Meeting, S e w York and New Jersey American Chemical Society Sections, New York, N. Y., Jan. 27, 1964. (20) Compare the 100-e.v. yields of alkali nitrates irradiated a t 30' with Coma y-rays, where G 2.21 (21) C. J. Hochanadel, Radiation Res., 16, 286 (1962).
-
REACTION OF ACTIVENITKOGEN WITH SULFUR
bution of radiation chemical effects to the recoil product distributioii probably does not exceed about 2%.
2501
Acknowledgment. This research was supported in part by the U. S. Atomic Energy Commission.
The Reaction of Active Nitrogen with Sulfur12
by J. A. S. Bett'b and C. A. Winkler Upper Atmosphere Research Group, Department of Ch.emistry, McGill University, Montreal, Canada (Received March 16, 1964)
The amount of nitrogen that reacts with Szvapor to form sulfur nitrides has been measured for three different initial concentrations of N atoms and several sulfur flow rates. A marked induction period preceded formation of any nitrides, and the maximurn concentration of Iz' atoms that appeared in the products was less than the initial 8 atom concentration. These results are explained by a mechanism in which the NS radical is formed in the initial reaction(s) and is rapidly destroyed in the presence of excess Tu' atoms. I n the absence of PI: atoms, the KS intermediate will either disproportionate or form stable sulfur nitrides both in the gas phase and at the surface of the reaction vessel. The infrared spectra of the products showed t h a t IY.S.1and a t least two other sulfur nitrides were present. The blue flame associated with the reaction may be attributed to a transition D ( 2 ) + C(*II) of the NS radical.
Introduction The reaction of active nitrogen with sulfur has been described briefly by Strutt,2 who sublimed sulfur into a stream of active nitrogen and obtained a yellow and a blue product. He suggested that these were NSd and a polynier of SS, respectively. Moldenhauer and Zimmerman3 found, in addition to these, a red compound, S2Se,when solid sulfur was heated to 100' in a nitrogen discharge tube. The present study was made to obtain quantitative information on the react>ionbetween active nitrogen and sulfur vapor, for comparison with the analogous reaction with oxygen, which has been investigated previou~ly.*-~ Experimental The apparatus was essentially a conventional fastflow system with a cylindrical, horizontal reaction tube. One stream of nitrogen, with a flow rate of 140 prnoles/sec., was subjected to an electrical discharge
to produce the active nitrogen, which then passed into the reaction tube. A second nitrogen stream, 50 wmoles/sec., was passed through a furnace at 450' and entered t h e reaction tube through a concentric jet 2 mm. in diameter. The pressure was 3.0 mm. in the discharge tube and 4.5 mm. in the furnace. Sulfur was contained in a vessel that could be niaintained at any desired temperature between 100 and 250". A third stream of nitrogen was passed over the (1) (a) Presented a t the 145th National Meeting of the American Chemical Soriety, New York, N. Y.,September, 1963; (b) postdoctoral Research Fellow. (2) R. J. f3trut.t. Proc. Roy. Sac. (London), A88, 539 (1913). (3) W. Moldenhauer and A. Zinimerman. Ber., 62, 2390 (1929). (4) C. B. Kistiakowsky and G. G.Volpi, .I. Chsm. Phys.. 27, 1141 (1957). (5) C . Mavroyannis and C. A. U'inkler. International Symposium 011 the Cheniistry of the Lower and Upper Atmosphere, San Francisco, Calif., April. 1961. (6) M. A. Clyne and B. A. Thrush. PTOC. Roy. SOC. (London), A261, 259 (1961).
Volume 68, Number 9 September, 1964
