XOTES
2477
involve monotadicals. I n addition, since oxygen had no effect on the product yields, it might be concluded that long-lived triplets were not involved in the photochemistry of BCHD. The decomposition probably proceeds through the intermediate formation of highly reactive biradicals I and 11. The decomposition of bi-
I1
I11
radical I could give cyclopentadiene and acetylene, while biradical I1 could rearrange to give biradical I11 and finally toluene. The rearrangement of a biradical of the above type is known in terpene chemistry.9r10
Acknowledgment. The author is grateful to Drs. K. 0. Kutschke and R. A. Bgck for their interest in this work. (9) H. Pines and J. Ryer, J . Am. Chem. SOC.,77, 4370 (1955). (10) R. L. Burwell, Jr., ibid., 73, 4461 (1951).
Time (minutes) Figure 1. Variation of rate of formation of cyclopentadiene and acetylene with time.
y-Radiolysis of Ammonium Perchlorate1*, by George Odian,Ic Terese Acker, and Thomas Pletzke Radiation Applications Inc., Long Island City, New York 10111,
Since we were unable to observe any emission visually, it is assumed that the molecules of BCHD do not dissipate energy by fluorescence a t wave lengths -36007000 A. Over a range of pressure the total quantum yield (Tables I and 11) for decomposition was 0.55 f 0.02; thus, it seems likely that 45% of the excited molecules were internally converted to the ground state. While the photodecomposition of BCHD presumably proceeds via some excited state, the almost negligible effect of added gas and temperature and the independence of the quantum yields on the pressure indicate that any such excited species had too short a life to suffer collisional deactivation under our experimental conditions. In view of the energy (112 kcal.) per quanta of 2537-A. radiation, this is not a t all surprising. This is also consistent with the fact that in the liquid phase (Table 11), where one would expect very many more collisions among the molecules, the quantum yields ( @ c C 1 H 1and @ c C awere ~ J lowered by a factor of 4. It is riot clear why the quantum yield for the production of toluene was not affected, unless it originates from a different electronic excited state altogether. It is to be noted that nitric oxide behaved as an inert gas in this system, which suggests that the decomposition did not
and Department of Chemical Engineering, Columbia University,
New York, New York
10027
(Received February 1 , 1966)
Although the radiolysis of various alkali and alkaline earth perchlorates has been extensively studied, 2, t h a t of ammonium perchlorate has received little attention. Freeman and co-worker~,~ in one of the few reports on the chemical products of ammonium perchlorate radiolysis, have found chloride, chlorate, nitrite, and nitrate to be present. We wish here to describe the results of our studies on solid ammonium perchlorate radiolysis. (1) (a) Presented in part at the 148th National Meeting of the American Chemical Society, Chicago, Ill., Sept. 1964. (b) The authors wish to acknowledge gratefully the support of this work by the Air Force Office of Scientific Research, Propulsion Division, under Contract AF 49(638)-1125. (c) To whom inquiries should be addressed: Department of Chemical Engineering, Columbia University, New York, N. Y. 10027. (2) (a) L. A. Prince and E. R. Johnson, J . Phys. Chem., 69, 359, 377 (1965); (b) L. A. Prince, Ph.D. Thesis, Stevens Institute of Technology, 1963. (3) H . G. Heal, Can. J . Chem., 31, 91, 1153 (1953); 37, 979 (1959). (4) (a) E. S. Freeman and D. A. Andersoh, J . Phys. Chem., 63, 1344 (1959); 65, 1662 (1961); (b) J. 9. Hyde and E. S. Freeman, i b i d . , 6.5, 1636 (1961); (c) E. 9. Freeman, D. A. Anderson, and J. J. Campisi, ibid., 64, 1727 (1960).
Volume 69, Number 7
July 1966
2478
NOTES
Reagent grade ammonium perchlorate (Matheson concentrated sulfuric acid solution) followed by the Coleman and Bell) was recrystallized twice from deformation of F e ( S 0 ) 2 + whose absorption at 525 mp ionized water, dried, and then irradiated in stoppered was then determined. test tubes with cobalt-60 a t 10-15" a t a dose rate of As indicated above, ClO? and C102- were found not 0.36 Mrad/hr. No precautions were taken to exclude to be products of ammonium perchlorate radiolysis air from the specimens prior to radiolysis. The irin any appreciable amount. The same was observed radiated ammonium perchlorate was dissolved in for NO3- plus NO?-. CIOa-, C10-, Cl?, and C1water and analyses were performed for chlorate, chlomere found to be the major products of the radiolysis rine dioxide, chlorite, hypochlorite, chlorine, chloride, of ammonium perchlorate and the results are shown and the total of nitrite plus nitrate. All of the anain Figure 1. The initial G values were calculated and lytical procedures were checked out with known mixtures of the various chemical species and it was ascertained that interferences were not present. Chlorine dioxide, chlorite, hypochlorite, and chlorine were analyzed by their oxidation of iodide ion to iodine in a manner similar to that of Johnson and Prince.? The iodine was determined spectrophotometrically 0 " 250 at 350 mp. In basic media (pH 8-9), C10- and Cl? V would be reduced to C1-, ClOz to ClOz-, while C l O c 2 z would be unaffected. On acidification to pH 1-2, 5 200 a C102- (both CIOz- formed from NH4C104 radiolysis II: 0 and that from the reduction of ClO? in basic media) ffl 150 would also be reduced (to C1-) in addition to the CIOz, 0 C10-, and Clz. Since no additional oxidation of iodide 5 0 a was observed on acidification, it was concluded that 2 100 both ClOz and ( 3 1 0 2 - are not products of ammonium I perchlorate radiolysis. Thus, the basic oxidation of n -I iodide ion a a s due to C10- plus Clz. The yields of 50 these two species were separated by perforniirig the iodide oxidation analysis with and without prior flashboiling. Flash-boiling resulted in the expulsion of C1, 0 0 20 40 60 80 too I from the solution of irradiated ammonium perchlorate R A D I A T I O N DOSE (MRADS) and was accomplished by heating the solution to boiling. Figure I. Yields in ammonium perchlorate radiolysis The oxidizing power of the solution of irradiated ammonium perchlorate toward ferrous ion in acidic media was also observed in a procedure similar to that are given in Table I. It can be seen from Figure 1 that of Johnson arid Prince.? The ferric ion was determined all yields except that of C103- were essentially indespectrophotonietrically at 305 nip. In addition to the pendent of dose over the range studied. The C103C10- and Clz,C103- is also reduced (to C1-) by ferrous yield, however, was observed to fall off and decrease ion. Thus, the C103- yield is obtained by the difa t the higher doses. This probably indicates that the ference between the iodide and ferrous oxidations. C103- is undergoing radiolytic decomposition. This Chloride ion was determined by a modification of the Volhard procedure utilized by Burns and l l u r a ~ a . ~ is very similar to the results of Heal3 on the radiolysis of potassium perchlorate although Johnson and Prince? An excess of silver nitrate was added to the sample did not observe the effect. and the excess silver ion was back-titrated with thioThe ammonium perchlorate radiolysis differs cyanate ion. The yield must be corrected to take into markedly in two respects from those of the metal account the fact that hypochlorite also reacts with perchlorates studied by Johnson arid Prince. The silver ion (yielding AgCl and 0 2 ) . The sun1 of nitrite plus nitrate was determined by a modification of the procedure used by Yorwitzo in the analysis of nitrate. This involved the reduction of (5) E. A. Burns ana R. F. Muraca, A w l . C h i m . Acta, 23, 136 (1960). both nitrate and nitrite to nitric oxide by ferrous ion (in (6) G. Norwits, A n a l . Chem., 34, 227 (1962).
i
c
\
c
T h e Journal of Physzcal Chemistry
NOTES
2479
radiolytic decomposition of ammonium perchlorate is greater than that of the alkali or alkaline earth perchlorates by a factor of ca. 2-5 (depending on the particular metal perchlorate considered). Another difference is that Clz, while a major product (G = 1.2) of ammonium perchlorate radiolysis, is not reported a t all in the radiolysis of the metal perchlorates. The “crystal free volume” (the difference between the volume per mole of crystal derived from the X-ray density and the volume per mole of constituent ions’) has been succrssfully used to correlate the radiolytic yields of the metal perchlorates* and also the alkali metal bromate^.^ The radiolytic yields in those two groups of compounds had been found to increase
Table I : Ammonium Perchlorate Radiolysis Product
c103c10* c102 c10 c12
c1-
NOoa
G
=
+ NOz-
G value”
1.3
