1015
NOTES
July, 1957
TABLE I1 INFRARED SPECTRA OF METALLIC OXALATES A N D FREE OXALATE ION ( C M . - ~ ) asym.
Coinpd. (CZV)
bat
u(C-0)
a1
a1
KSAIOXS
1718,1695,1656
1404
&COO13
1710,
1658
K3Crox3
v(C-0)
bi
S(0-c-0)
905
822 806 824 810 817 807 804 795 804 790 772 768
545b
bau asym. S(0-c-0)
bl. asvm. S(C-c-0)
ai
1389
1290 1270 1257
900
1714,1684,1650
1390
1259
894
K,Feoxl
1712,1675,1641
1389
886
KLCIIOXI
1675
1272 1255 1280 1306 1316 1335 1316
KQNioxZ 0x2-
1637
1415 (1450)
1630
1485b 1450b
1625 1620
K~COOX~
1664b
..
b2u
b1g
(VI]) a
$!E%)
as
sym. u(C-0)
The assignment of these bands is not clear.
b
asyrn. a(c-c-0) bi
v(C-C)
897
.. ..
89gb
b3u
ag
v(C-C)
bi
sym.
aym. S(C-c-0)
S(0-c-0) ai
a1
581
43 1
483"
559
44F
476"
543
488
413"
532
503
538
485 507 524 518
.. ..
9
.
.. ..
..
bau syrn. 6(C-C-O)
443b aym. 6(O-C-O)
Raman data by Murata and Kawai.8
It is clear that the formation of the Cr-0 bond lengthens the C-01 bonds and shortens the C-011 bonds. Although the two C-Or and C-011 bond lengths are not equal in each pair, it is reasonable to suspect that this is due to poor resolution of the carbons as suggested by van Niekerk and Schoening.14 Therefore we assume Cz, symmetry for the oxalate ion coordinated to the metal. Thus, it is anticipated that, as the M-0 bond becomes stronger, lowering of symmetry will be more distinct, and the shifts of the fundamentals of the oxalates relative to that of the free ion will increase. Table I shows the classification of the 12 fundamentals of the oxalate ion in v h and CL"symmetries. Among those 12 fundamentals, 9 are in-plane and 3 are out-of-plane vibrations. The number of infrared active in-plane modes are only 4 for v h , but increases to 9 in Czv. Of these 9 fundamentals, we could observe 8 bands in the range between 1700 and 400 cm.-'. Their locations in various metallic oxalates are given in Table 11. Table I1 indicates that, as the metal is changed in the order of Ni2+, Co2+, Cu2+, Fe3+, Cra+, Coa+ and Ala+, 2v(C-O), asym. S(0-C-0), and asym. S(0-C-0) are shifted progressively to higher frequencies whereas 24C-0) and sym. S(C-C-0) are shifted to lower frequencies. Although some irregularity is seen in the AI complex, this might be due to the difference of A1 from the other metals in atomic weight and electronic configuration. As discussed above, it is reasonable to expect that, as the M-0 bond becomes stronger, the C-01 bond is more lengthened and the C-011 bond is more shortened, resulting in the shifts of v(C-01) and v(C-011) to lower and higher frequencies, respectively. The relation between the strength of the M-0 bond and the shifts of the bending modes
is not simple. It may be anticipated, however, that, as the two C-0 bonds become more uneven, asym. S(0-C-0) and asym. S(C-C-0) are shifted to higher frequencies and sym. S(C-C-0) and sym. S(0-C-0) are shifted to lower frequencies. Therefore, we conclude that the M-O bond becomes stronger in the order of the metals, Ni2+, Co2+, Cu2+,Fe3+, Cr3+,Co3+and A13+. This spectroscopic result is in good accord with the order of stability constant (pK1K2)l6for the divalent ions. Although the data of stability constants for trivalent ion are not available, the order obtained in this study, A1 > Co > Cr > Fe, is consistent with that of other metallic complexes which are coordinated by oxygen. Acknowledgment.-The authors wish to express their sincere thanks to Mr. S. Tanaka of the SunStar Tooth Paste Company for aid in obtaining the spectra in the KBr region. (15) For example, see A. E. Martell and M. Calvin, "Chemistry of the Metal Chelate Compounds," Prentice-Hall, Inc., New York, N. Y., 1952. p. 516.
HIGH-ENERGY ELECTRON IRRADIATION OF NEOPENTANE BY F. W. LAMPE Research and Development Division, Humble Oil and Refining Company Baytown, Teras Received Fsbmary $8, 1067
The author recently carried out studies of the high-energy electron irradiation of methanel which, in conjunction with the results of studies of secondary reactions in the methane mass ~ p e c t r u m , ~ - ~ suggest that the reactions of hydrocarbon ions with methane molecules are not only important but, indeed, may account for the majority of the over(1) F. W. Lampe, J . Am. Chem. Soc., 79, 1055 (1957).
(2) D. P. Stevenson and D. 0. Schissler, J..Chem. Phys., 88, 1858 (1955). (3) D. 0. Schissler and D. P. Stevenson, ibid., 84, 926 (1956). (4) F. H. Field, J. L. Franklin and F. W. Larnpe, J. Am. Chem. SOC.,79, 2419 (1967).
1016
NOTES
Vol. 61
sentative case of intermediate conversion only trace amounts of n-butane were found. The normal butane analyses were therefore not continued and the neopentane-n-butane peak is reported as all neopentane. Dosimetry.-It has been demonstrated’-9 that acetylene, when subjected to high-energy radiation, polymerizes to cuprene and benzene a t a rate which is dependent only upon the rate of absorption of energy by the acetyleiie. It is thus convenient to use acetylene as a dosimeter. In our gas phase irradiations the energy of the primary electrons is essentially constant through the entire path. of gas. For such a situation, we can write the basic equation for the energy lost per cm. path length by an electron traversing a gaslo as
-
=
01
NZB
(1)
where a is a constant which can be determined from irradiations of acetylene, N is the number of molecules per cm.*, 2 is the number of electrons per molecule, and B is the so-called stopping number of the molecule for electrons which can be calculated if the “average ionization energy”I0 is known. We assume the average ionization energy of hydrocarbons to be 11.5 e.v.10 in the calculation of B . Although this may not be exactly correct, the A E / A X values for hydrocarbons other than acetylene are in error only to the extent that the “average ionization energies” of these hydrocarbons are different. 01 was found, from the acetylene irradiations,’ to be 5.75 x 10-a0 e.v.-cm.2/electron for 1.7 mev. electrons. A E / A X for neopentane was then calculated from this 01 and the relative values of B for acetylene and neopentane.
Fig. 1.-Ethane
and propane formation a t 50 mm. and 300’K.
all conversion t o gaseous products. This has been further confirmed in a recent publication.6 Neopentane was chosen as the next subject for investigation for two reasons: (1) because of its symmetry it might behave quite similarly to methane which is apparently more reactive under highenergy irradiation than any other paraffins and (2) since neopentane shows no parent peak in its mass spectrum, every ionization event might be expected to result in a dissociation which could lead to an observed high reactivity. Experimental The radiation source, radiation vessels and irradiation procedures were described previously.1 Materials.-Phillips Research Grade neopentane was frozen out in liquid nitrogen and then allowed to distil slowly into an evacuated (10” mm.) storage bulb on the vacuum system. The middle third of the frozen-out sample was collected. Gas-liquid partition chromatographic analysis indicated that the resulting neopentane was 99.80 mole % with 0.1% of isobutane and 0.1% of nitrogen. Analyses.-The major gas-liquid partition chromatogram of the gas mixture was obtained with a benzyl cellosolve column previously calibrated with ure hydrocarbons. The methane-air peak was resoged by charging a sample of the gas mixture to a 5A molecular sieve column which permitted measurement of the amounts of nitrogen, oxygen and methane present. The ethylene-ethane peak was resolved by charging a sample of the gas to a dimethylformamide column. The n-butane-neopentane peak was resolved by use of a diethyl succinate column, and in a repre(5) G. G. Meisels, W. H. Hamill and R. R. Williams, Jr., J . Chem. Phga., 26, 790 (1956). ( 6 ) B. M. Tolbert and R. M. Lemmon, Radiation Research, 8, 52 (1955).
1
Results and Discussion The gaseous products formed and their 100 electron volt yields are shown in Table I. Figure 1 shows the formation of ethane and propane as a function of absorbed energy, and it is from such plots that the “G” values were determined. No compounds heavier than neohexane were found in the gas phase, but some liquid is formed in the reaction. I n the higher dosage experiments this liquid was visible on the inner walls of the reaction vessel, but no effort was made to recover it. Quantitative work on the liquid portion was limited t o atomic material balances on the gas phase. It is found, in this way, that the empirical formula of the liquid is approximately C,H2,. It is apparent from Table I that the reactivity of neopentane under irradiation is quite similar to TABLE I ENERGY YIELDSIN ELECTRON IRRADIATION OF NEOPENTANE A T 50 MM.AND 300’K. Component “c” neo-CsHI2 -G,6 f 2 . 0 CH4 1 . 8 f .6 0 . 3 1 f .OS CaHi CaH6 2 . 3 f .S 0 . 2 6 f .OS CsHe C3Ha 0.54 f . l o 0.33 f . I 1 CiHs 1.2 f .3 i~~-CdHio 0 . 2 2 f .07 iso-CsHis neo-CeHtc 0.34 f .I5 4 . 3 =I=1 . 1 Ht CHI units condensing 16 f7 (7) L. M. Dorfman and F. J. Shipko, J . Am. Chem. Soc., 7 7 , 4723 (1955).
( 8 ) S. C. Lind, D. C. Bardwell and J. H. Perry, {bid., 48, I556 (1926). (9) C. Roaenblum, THISJOURNAL, 62, 474 (1948). (10) W. Heitler, “Quantum Theory of Radiation,” 3rd ed., Oxford University Press, London, 1954, pp. 368470.
b,
NOTES
July, 1957 that of other paraffin hydrocarbons.6 It is also evident that quite a variety of products is formed and that we are dealing with an exceedingly complex reaction. From the number of gaseous products and the state of our knowledge concerning ion-molecule reactions in neopentane and ion-electron neutralization reactions of hydrocarbons in general, it is clearly impossible to write a detailed mechanism for this reaction. However, there are some features that deserve comment. It has been mentioned that no parent peak has ever been observed in the mass spectrum of neopentane. In addition, by far the major peak in the mass spectrum is that of mass 57. This is interpreted to mean that following the ionization of neopentane mostly the following occurs C(CHs)r+ +C(CIL)af
+ CH3
(1)
That methyl radicals are the predominant free radicals in this system has been demonstrated." l ' h e presence of methyl radicals immediately suggests that methane and ethane are formed by the usual reactions of abstraction and combination, that is CH,
+ C(CH& --+ CHd + (CHd3CCHz. CHI
+ CHI +CzHs
(2) (3)
The rates of formation of methane and ethane can, of course, be obtained from the G values and the energy absorption rate. Then the value of 1cz/k3'/2 can be calculated by the equation
1017
triquinoyl, there appears t o be relatively little information on related physical properties. There is little doubt that these compounds are five- and six-membered carbonyl rings, respectively, and it seems most likely that these are completely hydrated. 1-3 (EH)Z (HO )&-C(OH (HO)z
)z
&OH)Z \C/ (OH12 leuconic acid
/ \
(H0)zC (Hob
b
C(OH)z
&OHh \O/ (OH), triquinoyl
However, it is possible that some of the carbonyls might not be hydrated but that some water molecules are present as water of hydration. Thus, the investigation of the infrared spectra of these compounds would be worth while, as it readily would show any carbonyls which were not hydrated. Leuconic acid was prepared by the method of Nietaki and Be~ickiaer.~It decomposed at 155". (Nietaki and Benckizer report 160O.) Carbon-hydrogen analysis C, 26.85% (theor. 26.09%), H, 4.58% (theor. 4.38%) and density determinations from X-ray data (1.918, compared with a pycnometer value of 1.9487) agreed with the formula C&6&0. Triquinoyl was prepared by the method of Souchay and Tatibonet.8 Unfortunately, the yield was not large enough for analysis. The decomposition temperature was approximately 95", in agreement with the literature. The spectra were obtained on a Perkin-Elmer Model 13 spectrometer, used in direct mode of operation with NaCl prism and string drive to operate the slits. The spectra were obtained for the solid compounds either in Nujol mulls, or in KBr pellets.
The examination of the spectra showed essentially no absorption in the region from 1500 to 2000 cm.-l,' either for leuconic acid or for triquinoyl. Thus, there can be no unhydrated C=O groups in either compound. The spectra of the two compounds are very similar. For leuconic acid absorption bands are found a t (all frequencies are listed in cm.-l): -3500(s), 1465(w), 1390(m), 1320(m), 1122(5) , 1092(s), 924(m) and 912(m). For triquinoyl the bands are a t -3500(s), 1450(w), 1337(m), 1150(s), 1084(s) and 91O(s), These frequencies are characteristic for ordinary secondary alcohols.s As a further check on the hypothesis that the spectra of these two compounds are due entirely to the >C(OH)2 grouping, we have compared their spectra with that of the well known hydrate, chloral hydrate (C1,CCH(OH)2). Solid chloral hydrate has its absorption bands a t -3500(s), 1425(m), 1315(m), 1108(s), 1089(s), 980(w), 970(w) and 822(s). In the region (11) L. H. Gevantman and R. R. Williams, Jr., THISJOVRNAL,66, 509 (1952). above 1000 ern.-', the spectra of the three com(12) A . F. Trotman-Dickenson, J. R. Birchard and E. W. R. Steacie, pounds are thus very similar. Furthermore, the J. Chem. Phys., 19, 163 (1951). similarity of the spectra of all these compounds to the spectra expected for compounds with ordinary INFRARED SPECTRA AND THE STRUC- secondary OH groups is striking indication that TURES OF LEUCONIC ACID AND TRI(1) B. Homulka, Ber., 64, 1393 (1921); 65, 1310 (1922). (2) J. St. L. Philpott, V. J. Graham-Horgan and J. Watson, ReQUINOYL
where Qa is the rate of absorption of energy in e . ~ . / c r n .sec. ~ The value obtained for k2/k3'/' is 8.5 x 10-13. Trotman-Dickenson, Birchard and Steacie,12 in a study of the photolysis of acetone in the presence of neopentane, obtained a value for kz/k3'/a of 6.3 X a t 182'. Using their value of 10.0 kcal. for E, - 1/2 E3 one calculates at 300°K. (the temperature of this work) a value for k2/k3"' of 2.1 X which is less than that found in this work by a factor of about 400. Unless it is postulated that the methyl radicals formed in (1) are "hot," it is suggested that additional reactions that produce methane are occurring. Acknowledgment.-The author wishes to acknowledge the assistance of Messrs. T. P. Gorman and J. P. Keller in the irradiations and Messrs. W. C. Jones and A. V. Cruthirds in the analyses.
BY WILLISB. PERSON AND DALEG . WILLIAMS Department of Chemistry, State University of Iowa, Iowa City, Iowa Received March 16, 1967
I n spite of the rather unusual nature of the structures generally proposed for leuconic acid and
SeUTCh (London), I,273 (1948). (3) P. Souchay and F. Tatibonet, J . ch(m. phys., 49, No. 7-8,C 108 (1952). (4) R. Nietrki and T. Benckizer, BsT., 18, 506 (1885). (5) R. N. Jones and C. Sandorfy writing in W. West, "Chemical Applications of Spectrosoopy"in the Weiaaberger aeries, "Technique of Organio Chemistry," Vol. IX, p. 430 ff., Interscienoe Publishera, New
York, N. Y..1956.
