Nov., 1959
1977
NOTES
Winkler and co-workers.' In general it was found that hydrogen cyanide was the major product of the active nitrogen reaction and the only one that contained nitrogen. Because of this they postulated that nitrogen atoms do not attack hydrocarbons by hydrogen atom abstraction but rather by a direct approach to the carbon atom. We have recently studied the reactions of active nitrogen with silanes and hydrocarbons and have found that significant quantities of ammonia are formed.
ucts from the benzene reaction, a dark brown unidentified material was deposited,
Experimental The active nitrogen was produced by a condensed discharge using the apparatus described by Winkler and COworkers.2 The discharge tube and reaction vessel were not oisoned. Prepurified Linde nitrogen was passed through a fquid nitrogen trap and then directly to the discharge tube. The nitrogen flow rate was maintained constant a t 1.2 X 10-6 mole/sec. which corresponded to a pressure of 1.2 mm. The reactant flow rate was determined by pressure decrease in a calibrated volume. The following hydrocarbond were used: purified %-hexane,* Phillips research grade cyclohexane and benzene, and Phillips pure grade neopentane. The methylamine and ethylamine were Matheson C.P. and the tetramethylsilane was Dow Corning purified grade. The amount of hydrogen cyanide formed was determined by gas liquid partition chromatography using a calibrated 2-meter didecyl phthalate column. Ammonia was identified by its characteristic infrared spectrum and determined quantitatively by its absorption at 968 cm.-l. Acetylene and ethylene were determined b infrared absorption a t 725 and 946 cm.-l, respectively. &,her products were studied by gas-liquid chromatography using a tetraisobutylene column.
*C4H14 C-CaHla CsHs CHiNHa CzRsNHn
TABLE I
ACTIVENITROGEN REACTIONS Flow
m.t,n. _ -__,
Reactant (CHI)& (CHa)rSi
x
10'
moles/ Temp., HCN NHI CZHI CnHi Cs 880. OC. - - - - - - m o l e s / s e c . X 10728 1 . 6 0.32 0.17 .. .. 40 250 25 4.5 .BO 0.30 .. .. 28 0.7 .35 .. 11 10 10.2 14.2 14 15.5 3.3
250
3.2
250 250 250 250
4.9
1.2 1.0
5.8 4.9
0.7 0.9
5.3 2.0
4.7
250
1.3
.. ..
..
..
1.4 1.5 0 0 0 0.35 0.11 1.0 0.6 1.2
,.
CI
..
.. .. ..
0.5 0.3 0.5 0.3 0 (2.3) 0 0
..
..
The reaction with methylamine produced approximately equal amounts of hydrogen cyanide and ammonia. The amount of hydrogen cyanide formed was equal to the amount of methylamine reacted. Freeman and Winkler6 have reported that the ammonia formed is about 25% of the hydrogen cyanide formed. The reason for this discrepancy is not apparent. I n the ethylamine reaction the ratio of ammonia formed to hydrogen cyanide formed was almost one-half. Small amounts of acetylene and ethylene were also formed. The formation of significant amounts of ammonia in the reaction between active nitrogen and hydrocarbons has not been reported heretofore. It appears unlikely that ammonia is formed by a series Results and Discussion of hydrogen atom abstraction reactions since, in The details of the active nitrogen reactions are the first step, imine radicals are formed which very given in Table I. In all cases it was found that likely disproportionate to hydrogen and nitrogen. ammonia was a significant reaction product. With It is also known that for hydrocarbons the first step neopentane and tetramethylsilane the ratio of is appreciably endothermic.' The combination of ammonia to hydrogen cyanide was approximately nitrogen atoms with hydrogen atoms is known to 20 and 40%, respectively. The neopentane results, produce ammonia,6and it is conceivable that such with the exception of the ammonia formation, are a mechanism could account for the ammonia obin good agreement with the results of Onyszchuk served in the active nitrogen reactions. The uniand Winkler.4 The reaction of active nitrogen with fied mechanism proposed by Winkler and cotetramethylsilane produced a solid deposit on the workers can be adapted to account for the ammonia walls of the reaction vessel. Infrared examination formation by postulating that a given fraction of of the deposit indicated the presence of Si-N and the nitrogen atom-reactant complexes decompose Si-C bonds. It is of interest that the ratio of either to an amine radical or directly to ammonia. The author is indebted to R. S. McDonald for hydrogen cyanide from neopentane and tetramethylsilane is approximately the ratio of the considerable assistance with the infrared assignments. carbon atoms in each molecule. The reactions with hexane, cyclohexane and ben(5) G. R. Freeman and C. A . Winkler, ibid,, 69, 780 (1955). zene a t high temperature and high flow rates pro(6) B. Lewis. J . Am. Chem. Soc., 50,27 (1928). duced approximately the same yield of hydrogen cyanide and ammonia. In addition appreciable FLUID PHASES I N MUTUAL CONTACT: quantities of Cz, CSand C4 products were obtained FURTHER EXPERIMENTAL with hexane and cyclohexane whereas with benzene apparently only Cz and C4 products were CONSIDERATIONS formed. The Cq product results for benzene shown BYWILLIAMFox1 in Table I were obtained by gas chromatography 667 Oakland Avenue, Staten Island, N . Y . with a didecyl phthalate column. The hydrocarR6ceived February B6, 1868 bon product identifications were based entirely on retention time data and therefore can only be Presented in this communication are some fundaconsidered as tentative identifications. After mental physical facts regarding fluid phases in muwarm-up of the liquid nitrogen condensable prod- tual contact and a description of experimental approaches which will be extended to yield a new (1) H. G. V. Evans, G . R. Freeman and C. A. Winkler, Can. J . Chem., 84, 1271 (1956). method for the determination of absolute values of (2) P. A. Gartaganis and C. A. Winkler, i b i d . , 34, 1457 (1956). (3) H. A . Dewhurst, THIEJOURNAL,68, 15 (1858). (4) M.Onysrchuk and C. A. Winkler, ibid., 69, 868 (1956).
(1) Faculty of Police Science, Baruch School, City College of New York, New York, N. Y. Police Department, City of New York.
NOTES
1978
Fig. 1.
the tensions of fluid interfaces. Methods for the direct determination of relative values already have been presented.2J Figure 1 demonstrates the case where varying masses of methylene iodide were brought into contact with the same column of air projecting into the aqueous phase. Each half of the photographic plate was exposed with a different mass of methylene iodide suspended on the same column of air. All the phases were mutually saturated. The methylene iodide had been distilled under reduced pressure and the water distilled from a block tin system. The temperature was 25’. By directly superimposing the photographed images on another plate (Le., plate 1, Fig. 2),*it was determined with good precision that the angle through the aqueous phase at the edge of common contact was the same in each case. From Fig. 1 it is apparent that the magnitude of the force that can act to hold the methylene iodide on the gas phase, after equilibrium with respect to the interfaces has been established, must be at least equal to the gravitational force due to the mass of methylene iodide suspended under the conditions depicted in the right half of Fig. 1. It can therefore be concluded that the gravitational force due to the mass of methylene iodide suspended under the conditions depicted in the left half of Fig. 1must be less than the total force that can hold it on the gas phase. It is evident from Fig. 1 that the difference between the gravitational forces due to the different masses of methylene iodide suspended in each case cannot be accounted for by the difference between the lengths of the circumferences of mutual contact. From these experiments we may conclude that equilibrium between the gravitational force and the force that can act to hold one fluid phase on another in the presence of a third fluid phase, after equilibrium with respect to the interfaces has been established, i s not a necessary condition for equilibrium with respect to the interfaces. Since the gravitational force due to the mass of methylene iodide suspended in the left half of Fig. 1 (2) W . Fox, J . Chem. Phys., 10, 623 (1942). (8) W . Fox, J . A m . Chem. Soc., 67, 700 (1945).
Vol. 63
must be less than the force that can hold it on the gas phase we can also conclude that the “excess” final edge force is balanced all around the circumference of contact. It is significant t o note that even under the influence of the “excess” edge force the smaller drop of methylene iodide does not become extended over the gas phase but remains in a position that gives the constant, reliable, reproducible angle characteristic of the system under investigation. These experiments also lead to an understanding of the necessary requirements for the determination of the linear force intensity, dF/dL, along the massless circumference of mutual contact, after equilibrium with respect to the interfaces has been established. The mass of fluid phase suspended must be increased until the maximum mass that can be suspended along the circumference of mutual contact is determined. The determination of this mass and the length of the circumference of common contact will give the linear force constant operative. The magnitude of this linear force constant can be related to the linear force constants of the interfaces concerned and thus give a new independent method for the determination of the absolute value of the tension that is manifested at the boundary limit (the edge) of each of the interfaces. Acknowledgments.-The author wishes to thank his wife, who carefully reviewed the manuscript, and Professor Arthur W. Thomas of Columbia University, who stimulated and encouraged this research.
t
‘
KINETICS OF CONSECUTIVE COMPETITIVE SECOND-ORDER REACTIONS BY P. R. WELLS’ College of Technology and Commerce, Leicester, England Received March 2SV1969
Due to the complex nature of the mathematical expressions obtained most treatments of consecutive competitive second-order reactions lack generality since simplifying conditions2 or approximationsa are employed. The following treatment is general as far as equation 8 and is essentially equivalent to those due to Higgins and Williams,‘ to Frost and Schwemer,6to McMillan6 and to Riggs,’ but yields an expression more suitable for the present purpose ( 1 ) Iowa State College, Ames, Iowa, U.S.A. (2) Cf. Jen-Yuan Chien, f. A m . Chem. Soc., 70, 2256 (1948); M. TalAt-Erben, J . Chem. P h y s . , 26, 75 (1957). (3) Cf. K. Ingold, J . Chem. SOC.,2170 (1931); F. H. Westheimer, W. A. Jones and R. A. Lad, J . Chem. Phya., 10, 478 (1942).
C.
(4) H. G. Higgina and E. J. Williams, Aust. J . Sci. Res., AS, 572 (1952). (5) A. A . Frost and W. C. Schwemer. J . A m . Chem. Soc., 74, 1268 (1952). (6) W . H. MoMillan, ibid., 79, 4838 (1957). (7) N. V. Riggs, Aust. J . Chem., 11, 86 (1958).
I
