1020
NOTES
Lorentz and polarization factors, t o get a set of values proportional to the F2’s, the Patterson series (Fig. 1) was calculated with the aid of BeeversLipson strips.’ In this projection, as well as in the electron density maps below, values were calculated at intervals of c/120 along c, and of b/30 along b. From the Patterson projection the Coordinates of the Br atom were estimated t o be, approximately, y/b = 0.033 and x/c = 0.206. These coordinates were used to determine the signs of most of the strong reflections, and a first Fourier series was calculated. After two more refinements only the signs of a few weak reflections were still uncertain, and the signs of all the strong or moderately strong reflections were known with certainty. Figure 2 shows the third refinement, calculated with all but nine of the available terms. Using the atomic coordinates obtained from this projection by analytical interpolation,* the reliability index for the observed Okl reflections is R = 0.29, when an artificial isotropic temperature factor exp [- B(sin O/h)2],with B = 5.17 X 10-ls cm.2,is introduced and the contribution of the oxygen to the reflections is calculated as one-half of that corresponding t o a regular oxygen atom.g Discussion I n the Fourier projection, all the atoms are resolved and have about the expected electron content, except the oxygen atoms, which do not appear a t centers of symmetry, but are linked to the nitrogen atoms, in the number of two per molecule, each with approximately one-half the correct number of electrons. If the crystallographic evidence in favor of space-group P21/c corresponds to the truth, the apparent center of symmetry in the molecules, and the halving of the heights corresponding to the oxygen atoms in the a-projection, call for a disordered molecular arrangement, whose statistical effect is t o increase the true symmetry of the molecules. There is no evidence of diffuseness in the reflections recorded, so that our case recalls very closely the structure of pchlorobromobenzene, where, according to investigations of Hendricks’O and Klug,’l two “centrosymmetrica1;j”molecules are contained in a unit cell requiring four asymmetric units. Likewise, in the structure of 2-amino-4methyl-6-~hloropyridine,’~the maxima corresponding to chlorine atoms and methyl groups were found t o be identical, with an electron content intermediate between that of the halogen and the methyl group. Some similarities among these structures do exist. I n each case the molecules are approximately planar, and are almost perpendicular to the shortest cell axis. The space group is also the same, and Acta Cvyet., 2, 131 (1949). (8) A. D. Booth, “Fourier Technique in X-Ray Organic Structure Analysis.” Cambridge, 1948, pp. 62-65. , (7)
(9) A list of observed and calculated amplitudes of OM-reflections has been deposited as Document number 5591 with the AD1 Auxiliary Publications Project, Photoduplication Service, Library of Congress, Waahington 25, D. C. A copy may be secured by citing the Document number and by remitting $1.26 for photoprints, or $1.25 for 3.5 mm. microfilm in advance b y check or money order payable to: Chief, Photoduplication Service, Library of Congress. (10) B. Hendrioks, 2. Kriet.. 84, I ( 1 9 3 3 ) . (11) A. Klug, Nature, 160, 670 (1947). (12) C. J. B. Clews and W. Coahran. Acta Cwrt., 1, 4 (1048).
Vol. 62
the statistical symmetry acquired by the molecules through disorder brings about a somewhat closer packing than would be achieved in an ordered structure. As far as 4,4’-dibromoazoxybenzene is concerned, it should also be noted that azoxy compounds are known to form liquid crystals, indeed more than one liquid crystal form has been observed for some azoxy derivatives.13 It is possible that the presence of disorder in crystalline 4,4‘-dibromoazoxybenzene bears some relation to the liquid crystal state. Finally, a word should be said about the reliability index. I n view of the apparent simplicity of the structure the value of R = 0.29 is fairly high, even if we take into account the fact that no correction for spot-shape, absorption and the like were introduced, and individual anisotropic temperature factors were not used in the computation of the structure amplitudes. Comparable data are lacking. Klugll does not give information as to the sort of agreement obtained for p-chlorobromobenzene but explains some false details appearing in the Fourier projections as due to poor intensity data. Similarly, Clews and Cochran12do not give any R value for 2-amino-4-methyl-6-chloropyrimidine. The R value for the b-projection of 2-amino-l, 6-dichloropyrimidine, isomorphous to it, is given as R = 0.24. It is likely that a somewhat higher value was found for 2-amino-4-methyl-6-chloropyrimidine, probably of the same order that we find for 4,4‘-dibromoazoxybenzene. In conclusion, I wish to thank Mr. R. Levetan, of our laboratory, for supplying the crystals of 4,4‘dibromoazoxybenzene prepared by the dextrose reduction method. (13) D. VorlBnder, Trans.Faraday Xoc., 29, 913 (1933).
PRODUCTS OF THE RADIOLYSIS OF WATER CONTAINING BENZENE AND AIR BY JEROME GOOD MAN^ AND JOSEPH STEIQMAN* Department of Chemistry Polytechnic Institute of Brooklyn. Brdoklyn, N. Y . Received December 16, 1Qb7
I n the high-energy irradiation of water saturated with benzene and containing dissolved air, phenol and hydrogen peroxide are formed until oxygen is depleted; phenol is then produced at a reduced rate, and biphenyl appears in increasing yield.a Reported values for G(pheno1) (Le., molecules of phenol formed per 100 electron volts absorbed) vary from 1.32 to 3.05, with most values falling between 2.2 and 2.7. They are reported in Table I. We have found that a previously unreported substance, which we have not succeeded in identifying, is also formed. This material behaves like phenol in most of the analytical methods employed by previous investigators. As a consequence, where its presence is not recognized, the reported (1) In partial fulfillment of the requirements for the degree of Doator of Philosophy in Chemistry at the Polytechnic Institute of Brooklyn. (2) To whom inquiries should be addressed. (3) E. Colliion and A. J. Swallow, Chsm. Rats., 86, 605 (1956).
-
NOTES
August, 1958 TABLE I SUMMARY OF G(PHENOL)VALUES Dose rate, r./min.
3000 4500 333 18.3 1200 1200 700 560
Radiation
200 kvp. X-rays CONgamma 23 MeV. X-rays CONgamma Corn gamma Cow gamma 190 kvp. X-rays Cow gamma
1021
0.9
'roripinol
unextroclsd moleriol
I
Wphenol) Reported
Ref., year
2.30 2.7 2.74 3.05 2.2 2.6 1.32 2.64
(4) 1949 (5) 1952 (6) 1953 (6) 1953 (7) 1954 ( 8 ) 1954 (9) 1955 (10) 1957
0.8
0.7 0.6 ai
0.5 G(pheno1) value will be too high. The extent of e the errors cannot be stated with certainty, since the D bulk of our experiments were performed with softer 4 0.4 radiation. I n addition, the substance appears to be somewhat unstable, so that its contribution to previous phenol assays is difficult to estimate. Most 0.3 of our samples were exposed to X-rays from a Machlett OEG-50T tube operating a t 40 kvp. (unrectified) and 25 ma,, with sample exposures 0.2 ranging from 5 to 90 minutes (15 minutes being required for oxygen depletion). Several experi0.1 ments were also carried out with filtered 100 kvp. X-rays and with filtered 210 kvp. X-rays. The results obtained with the harder radiations are qualitatively similar t o those found with the softer 240 260 280 300 320 340 300 380 400 radiation, but numerically different. SpectroWave length, mp. photometric measurements were made with the , of extracted and unextracted processand Instrumentscompany recording at- Fig. 1.-Absorption spectrum irradiation yields. tachment for the Beckman DU sDectroDhotometer. Figure 1 shows the spectrum of typical irradiated solution of benzene in aerated water. 0.6 It can be seen that there is an absorption peak at 345 mp? and a second a t 270. When the same 0.5 solution is extracted with ether (a procedure which quantitatively removes phenol, benzene and diphenyl), a peak remains a t 270 mp in the water $ 0.4 layer, together with that a t 345 mp; the latter C appears to be little affected by the extraction. If ,?8 0.3 OH the p H of such a water extract is progressively P raised, the absorbances of both peaks are markedly a! increased, although the effect is much more pro0.2 nounced at 270 mp than a t 345 mp. If the water extract (which is initially at 'pH 4.0 to 4.4 after 0.1 irradiation) is made alkaline to pH 12 and then restored to pH 4.0, the peak a t 345 mp shows very little change, whereas that a t 270 increases in 0 absorbance (from 0.410 to 0.580 in a typical case). 220 240 260 280 300 320 340 360 380 400 This strongly suggests an irreversible process Wave length, mp. which is accelerated in alkaline solution. Fig. 2.-Absorption spectrum of mater extract us. pH. The conclusion can be drawn that the hitherto unreported material absorbing a t 270 mp may con- only the corrections we have found in our experitribute t o the assay for phenol unless a correction ments (using 40 kvp. X-rays) when analyses for is applied. The magnitude of the correction will phenol were carried out according to the methods depend upon the method of analysis and may also of previous investigators. When phenol was andepend upon the spectral energy of the radiation alyzed by direct measurement of the absorbance and the dose rate. Accordingly we are reporting at 270 mp of the irradiated solution without ether extraction'l the error was +29%. When phenol (4) G. Stein and J. Weiss, J . Chem. Soc., 3245 (1949). (5) T.J. Sworski, J . Chem. Phye., 80, 1817 (1952). was determined by the difference in absorbances a t ( 0 ) R. Freeman, A. B. Van Cleave and J. W. T. Spinks. Can. J . 290 mp between the original irradiated solution Cham., 81,448 (1953). and the solution adjusted to p H 12.56J,10-the (7) W. A. Selke, A. Czikk and J. Dempssy, A.E.C. N Y 0 3330 method originated by Sworski-the error was (1954). (8) T.J. Sworski, Radn. Res., 1, 231 (1954). +27%, following his method of calculation and (9) J. H. Baxendale and D. Smithies, J . Chem. Phys., 23, 604 assuming that measurements on the alkaline side (1955).
\
\
I
a
(10)P. Phung and M. Burton, Radn. Res., 7, 99 (1957).
(11) M. E.J. Carr, Nature, 167,363 (1951).
I
I
.
1022
‘
NOTES
were made after the measurements on the original irradiated solution. The sequence of measurements will affect the final result because of continuing irreversible increases in alkaline solutions of the absorbance of the peak at 270 mp. When phenol was determined by measuring the absorbance at 520 mp of an irradiated solution treated with Folin’s reagent (the method employed by Stein and Weiss4), the error was +IS%, since the water extract reacts with the reagent. If the determination was made at 760 mp after reagent addition,6 the error was +14%. The only previously reported method for phenol assay which required no correction in our experiments was that based on the extraction of the irradiated solution by ether prior to the phenol determinati~n.~ The peak at 345 mp has been reported recently by other investigators,‘OJ2 but that at 270 mb has not previously been identified with a new material. Figure 2 shows the variation in spectrum of the water extract as the pH is progressively lowered. It can be seen that the peak at 345 mp practically disappears in sufficiently acid solution, while the absorbance at 270 mp is not reduced very much. However, there are two clearly defined isosbestic points at 315 and 280 mp, strongly suggesting an equilibrium between two species. The change in absorbance at 345 mu is most marked near a p H of approximately 2.3, which is in accord with the marked acidity developed by these solutions after irradiation. In our measurements the pH of irradiated solutions varied from 4.0 to 4.4; one previous paper has reported a similar acidity.6 In contrast to its behavior in alkaline solutions, the system appears to be reversible on the acid side. An attempt was made to recover enough material for infrared analysis by room temperature evaporation. The collected product was brown and non-crystalline, and charred slowly without giving a definite melting point. The infrared spectrum showed broad peaks characteristic of various carbon-oxygen bonds, suggesting a complex mixture. It is possible that decomposition or condensation had occurred during evaporation. Polarographic examination of an irradiated solution showed a half-wave potential at 3-0.059 volt (against S.C.E.), which is 0.020 volt more positive than that of hydroquinone. Irradiation of dilute phenol solutions in water showed that the new material or materials did not arise as a result of further reaction of alreadyformed phenol, since no peak at 345 mp was observed. Experiments in which irradiation was continued after oxygen was depleted showed that the ratio of phenol formed to the unknown material formed remained approximately constant. Weiss and COworkers have recently detected traces of catechol, hydroquinone and quinone, in addition to larger yields of what may be mucondialdehyde (2,4diene 1,6-hexadione).la They reported that it (12) M. A. Khenokh and E. M. Lapinskaya, First All-Union Conference on Radiation Chemistry (Academy of Sciences, U.S.S.R.) (A.E.C.tr-2925, p. 23,1957). (13) M.Daniels, 6.Saholea and J. Weiss, J . Cksm. Soc., 882 (1956).
Vol. 62
was not formed in air-free solutions; in addition, it shows no peak absorption at 345 mp. For these reasons, we consider that the material we are describing is not mucondialdehyde. We have been unable to identify the material or materials which are responsible for the absorbance peaks at 270 mp and at 345 mp. A survey of the ultraviolet spectra of benzenoid compounds listed by Hershenson14did not reveal any materials whose spectra and other properties corresponded t o those of the aqueous extract. Acknowledgments.-We wish to acknowledge a grant from the Society of Sigma Xi which aided in the purchase of the X-ray tube. We also wish to thank Mr. Irving Feuer for assistance in some of the work. (14) H. M. Hershenson, “Ultraviolet and Visible Absorption Spectra,” Academic Press. Inc., New York, N. Y.,1956.
INORGANIC COMPLEX COMPOUNDS CONTAINING POLYDENTATE GROUPS. XVIII. THE STABILITY OF IRON(I1) AND MANGANESE(I1) TETRAETHYLENEPENTAMINE COMPLEXES AND THEIR REACTIVITY TOWARD OXYGEN B Y HANSB. JONASBEN, ANNEKE SCHAAFSMAI AND
WEB TERM AN^
LOWELL
Contribution of the. Richardson Chemistry Labqratoriea of Tulane Unzverszty, New Orleans, Louzszana Received February 3, iDb8
The coordinating ability of higher polyamines has been investigated extensively during the last decadeat4 since these complexes have been of interest because of their catalytic behavior.6 The present study was undertaken to determine the formation constants of the iron(I1) and manganese(I1) ions with tetraethylenepentamine (abbreviated tetren) by the method of Bjerrume using the basicity constants of tetren previously determined as well as the equations previously derived.7 Experimental Technical grade tetren obtained from Carbide and Carbon Chemicals Cor oration was purified by precipitation as the pentahgdrockoride from ethanol solution. It was then recrystallized from a methanol-water mixture. Purity of the amine was determined by potentiometrio titration, chloride determination and measurement of the rimary amine content by the Van Slyke method as descrifjed preGious1 .7 A stocz solution of Mn(I1) was prepared by dissolving Mn(C10& in water; it was kept under deoxygenated nitrogen gas. The solution was standardized by precipitation as the manganese ammonium phosphate. Iron(I1) Derchlorate (Durchased from G. Frederick Smith Chemical ‘Corporationj’ standard solutions were prepared and kept (I) Abstracted in part from the Ph.D. dissertation of Anneke Sohaafsma, Tulane University, 1955. (2) Abstracted in part from the Ph.D. dissertation of Lowell Westerman, Tulane University, 1958. (3) H. B. Jonassen and A. W . Meibohm, THISJOURNAL, 66, 726 (1951). (4) G . Sohwarzenbaoh, Helv. Chim. Acta, 38, 947 (1950). ( 5 ) H. L. Williams, et al., 3. A m . Chem. Soc., 76,3321 (1954). (6) J. Bjerrum, “Metal Ammine Formation in Aqueous Solutioa,’ P. Haase and Son, Copenhagen, 1941. (7) H. B. Jonasaen, F. W. Frey and A. Sohaafsma, THISJOURNAL, 61,504 fl947).
*
