1078
J. GOUBEAU, E. L. JAHN,A. KREUTZBERGER AND C. GRUNDMANN
Vol. 58
TRIAZINES. X. THE INFRARED AND RAMAN SPECTRii OF 1,3,5-TRIAZINE'.2 BY JOSEFGOUBEAU, EVAL. JAHN,ALFREDKREUTZBERGER AND CHRISTOPH GRUNDMANN Laboratory of Inorganic Chemistry, Technische Hochschule Stuttgart, Germany, and The Ohio State University Research Foundation, Columbus, Ohio Received May $0,1964
A comparison of the infrared spectrum of the recently discovered trimer of hydrocyanic acid, C3H3N3,with those of some 1,3,5-triaaine derivatives on the one hand and with the Raman spectrum of CaHsNs on the other hand results in physical evidence besides the chemical proofs that CsH3Na is 1,3,btriazine, the long sought parent substance of so many l,3,5-triazine derivatives.
It was recently reported3 that the compound first prepared by Nef4and thereafter called "dimeric hydrocyanic acid," CzHzN2,is not a dimer a t all but is really a trimer of hydrocyanic acid, C3H3N3. As mentioned in this preliminary communication, both chemical and physical methods were used in order to assign to C3H3N3 its constitutional formula. While the pure chemical results have appeared elsewhere,z some of the physicochemical facts establishing the constitution of C3H3N3are presented here. The empirical formula C3H3N3allows to construct several constitutional formulas ; those with greater probability are listed as
N
N h = "
H
A HC-NH
IJ
N-
A H < N S C C
B H H HN=C-N=C-N
C
D
At the outset all those ring structures like type B containing an odd number of atoms in the ring can be excluded, since C3H3N3 on hydrolysis yields HCOOH and NH, quantitatively,6 thus making impossible the presence of C-C or N-N bondings. T o distinguish between A, C and D the infrared and Raman spectra were measured. In analogy t o 2,4,6-triethyl-1,3,5-triazine6the infrared spectrum of C3H3N3was determined a t first in a carbon disulfide solution (Fig. 1, I) and then compared with those of 2,4,6-trimethyl-l,3,5triazine (Fig. 1, II), 2,4,6-triethyl-1,3,5-triazine (Fig. 1, 111) and cyanuric chloride (Fig. 1, IV). However, that comparison was unsatisfactory insofar as carbon disulfide itself has a broad absorption band between 1400-1600 cm.-', covering in that range all bands of the dissolved substances. Therefore the infrared spectra of these four compounds (1) This article is partially based on work performed under Project
116-B of The Ohio State University Research Foundation, sponsored by the Mathieaon Chemical Corporation, Baltimore, Md. (2) Preceding communication: C. Grundmann and A. Kreutzberger, J . A m . Chem. SOC.,76, 5646 (1954). (3) C. Grundmann and A. Kreutzberger, {bid.. 76, 632 (1954). (4) J. U. Nef, Ann., 287, 377 (1895). (5) L. E. Hinkel, E. E . Ayling and J. H. Beynon, J . Chem. Soe., 676 (1935). (6) T. L. Cairns, A. W. Larchar and B. C. McKuaick, J . A m . Chem. Soc.. 74, 5633 (1052).
were then taken in carbon tetrachloride solutions which showed that each of the four spectra contained two very strong, fairly well separated bands just in that region where the aforementioned carbon disulfide band covers everything. These two bands are very characteristic for all four substances and are obviously due to the triazine ring system. Thus, the infrared spectra of the carbon disulfide and carbon tetrachloride solutions supplement each other in yielding extensive and informative infrared spectral data of these compounds (Fig. 2, I-IV). From the similarity of these four spectra the conclusion can be drawn that of all the possible constitutions structure A possesses the greatest probability. For comparison with the Raman spectrum of C3HIN3the data are compiled in Table I. These data indicate spectra with a relatively small number of lines, this in turn pointing to a highly symmetrical molecule structure as is represented by type A only. Since in both the Raman and the infrared spectra no lines of a triple bond, being expected in the range of 2000-2200 em.-', were observed, structures like C and D could now be definitely excluded because their terminal isonitrile groupings ought to exhibit, a frequency at 2100 em.-'. Thus both chemical and spectroscopical results point a t formula A only, wherefore a discussion of the spectroscopieal data related to structure A follows. TABLE I Raman
536 ( 0 ) 594 ( 0 ) 676 (2)
Infrared
Class
...
E" E' E'
...
673 m.s. 735 8.
A2 If
E"
921 ( I / ? ) 991 (4)
A1'
1070 V.W. AI '
1133 (4) 1404 (O?) 1560 (1)
(3025) (3046)
1170 m.
A2 "
1410 V.S.
E' E'
1560 V.S. 1775 V.W. 1850 V.W. 1950 V.W. 3025 V.W.
E'
Ai The triazine molecule possesses the symmetry Dah; the symmetrical properties (Table 11) lead to 10 Raman active vibrations, 3 of which are polarized and ? depolarized, and furthermore to 7 infrared vibrations, 5 of which are identical with the particular Raman vibrations.
Dec. , 1054
INFR.4RED AND
RAMANSPECTRA OF 1,3,5-TRIAZINE
1079
5
Fig. 1.--Infrared absorption spectra of 1,3,5-triazine (I),2,4,6-trimethyl-l,3,5-triazine (11),2 4,6-triethyl-1,3,5-triazine(111) and cyanuric chloride (IV), as determined in carbon disulfide solutions in a cell 0.005 in. thick.
TABLE I1 p = polarized, f = forbidden, dp = depolarized, ia =
inactive, a = active. Band t y p e Infrared
Class
Raman
AI’
P
AP’
f
AI ”
f
A?’‘ E’ E”
f dP dP
in ia ia a
Number of vibrations
3 2 0
a
2 5
ia
2
In the Raman spectrum 8 lines have been observed in the range up to 1560 cm.-l. The 2 high CH vibrations could not be found with certainty, since they are likely to collide with the lines of the Hg spectrum. With this considered, the 10 Raman lines required for this type of molecule are indeed present. From the number of infrared bands no conclu-
sions can be drawn, because infrared frequencies lower than 600 cm.-’ have not been measured and in the region above 1600 cm.-l several over- and combination vibrations occur. I n trying to assign the Raman lines observed to the particular vibrations, it must be said that any experimentally unobjectionable proof for the 3 lines of class A,’ is impossible yet, because of lack of polarization measurements. Solely from the intensity it may be inferred that the 2 strong Raman lines 991 (4) and 1133 (4)belong to the aforementioned symmetry class, since no infrared bands of these frequencies have been observed. The third missing vibration of this class must be a CH-valence vibration in the region of 3000 to 3050 cm.-I, but it could not be found by the Raman effect in spite of several attempts. Presumably it is masked by a shifted Hg line of 3040 em. - l . The 2 required vibrations of the class Az” which
J. GOUBEAU, E. L. JAHN,A. KREUTZBERGER AND C. GRLTNDMANN
log0
c
e +
0-
over. Thus all Raman lines and all strong infra-
A'"
(671)
Vol. 58
Dec., 1954
DIFFUSION AND MEASUREMENT OF HETEROGENEITY IN SEDIMENTATION
becomes particularly clear in the following comparison of these two spectra (Table 111),not only concerns the ring structure but also the binding forces prevailing in the ring system. Experimental The infrared data were obtained with a model 12C PerkinElmer spectrometer. The prism used was NaCl. The cell windows, too, consisted of NaCl with a mm. path length. The l.,3,5-triazine2 was purified by distillation over sodium metal, followed by slow sublimation a t 35’ bath temperature, these operations being carried out under exclusion of air moisture. For the Raman measurements the solvent (CCld or CBHB,respectively) was distilled onto the sublimed sample
1081
of triazine until a solution saturated a t room temperature was obtained. Then this solution was filtered through a frit into the Raman tube. The measurements were carried out in a customary apparatus, for 1.5, 4.5 and 8 hours in Cc1, solution and for 6 hours in C&& solution, uRing Hg 4358 as tho artivating light, source. Activation with Hg 4047 A. led to decomposition of the substance.
8.
Acknowledgment.-Two of the authors (C. G. and A. K.) are indebted to the Mathieson Chemical Corporation for their generous support of this work. Furthermore we wish to thank Mr. J. A. Curtis, Mathieson Chemical Corporation, Research Department, Niagara Falls, N. Y., for assistance in the infrared measurements.
BOUNDARY SPREADING IN SEDIMENTATION VELOCITY EXPERIMENTS. 111. EFFECTS OF DIFFUSION ON THE R.IEASURER;IENT OF HETEROGENEITY WHEN CONCENTRATION DEPENDENCE IS ABSENT BYROBEBTL. BALDWIN Contribution fronz the Department of Biochemiftry, University of Oxford, and the Department of Chemistry, University of Wzsconszn, Madison, Wisconsin Received M a y 20, 1964
The method of Baldwin 5nd Williams for finding g(s), a substance’s distribution of sedimentation coefficient, is based on extrapolation to infinite time. In this article the reliability of the extrapolahon procedure is studied with the aid of the analytic expression for g*(S) (the quantity used in extrapahtion) that results when g(s) is taken to be Gaussian. Secondly, a method is presented for obtaining the moments of the boundary gradient curve direct1 from the continuity equation, without having to solve the differential equation for the shape of the boundary, and it is stown that moments obtained in this way confirm Faxen’s solution of the differential equation. Finally, higher order terms are derived for the relation between p (the standard deviation of g(s)) and the standard deviation, u,of the boundary gradient curve.
Introduction The first article’ of this series considered how the width of a sedimenting boundary could be related to the average diffusion coefficient (D) and the heterogeneity in sedimentation coefficient ( s ) of the sedimenting substance, for the case in which s and D do not depend on concentration (c). It was found that the contributions to the boundary width from diffusion and from heterogeneity in s depend on different powers of the time, so that it is possible to obtain the distribution of sedimentation coefficient, g(s), by extrapolation to infinite time, in the same way that mobility distributions can be obtained.2 Costing3made a thorough theoretioal study of the extrapolation to infinite time and found the correct function of time t o use in order to obtain a linear extrapolation as infinite time is approached. The problem of obtaining g(s) under these canditions (ie., no dependence of s and D on c ) thus becomes one of reaching this range of time where Gosting’s limiting law holds. However, there is a basic limitation on the time for which an ultracentrifugal experiment may be continued : the experiment must stop before the boundary reaches the bottom of the cell. The definition of s (s = (dz/ d t ) / d z ) may be rearranged to show that the final
value of su2t is limited4 by cell and rotor design; consequently the length of an experiment can be increased only by lowering the speed of rotation and this decreases the resolution that can be obtained. This situation poses two important problems in finding g(s) by extrapolation to infinite time. First, how can one recognize for a given system whether or not the heterogeneity in s is sufficiently resolved that Gosting’s limiting law will hold in the range of time accessible to experiment? Second, if one is outside this range, what other method could be used to find g(s)? The second problem, although very interesting, is also very difficult and will not be considered here. I n order t o study the first problem, an analytic expression for the quantity used in extrapolation (g*(S), the “apparent distribution” of s) has been obtained for the case that g(s) is Gaussian. With this expression, the extrapolation to infinite time can be carried out with calculated values of g*(S)6and comparison of the extrapolated with the true values of g(s) rhade to show by how much the experiment departs from limiting law conditions. The success of the extrapolation is related to the resolution of the various sedimenting species obtained by the end of the experiment. The degree of resolution is oharacterized here by the ratio of the contributions to u2 (the second moment about
(1) J. W. Williams, R. L. Baldwin, W. M. Saunders and P. G. (4) It I t is the time elapsed at the end of the experiment, sw%f = Squire, .J. Am. Chevn. SOC.,74, 1642 (1962). In (zr/zo) < 0.2, where co and SI are the initial and final positions of (2) R. L. Baldwln, P. M. Laughton and R . A. Alberty, THISJOUR- the boundary. NAL, 66, 111 (1961). (5) T h s method was used’ to check on the reliability of mobility (3) 4,J, Goeting, J . A m , Chem, Hoc., 74, 1548 (1952). distributions obtained by extrapolation t o infinite time.
