the neighborhood of the melting point of the steroid, in the hope of providing additional information on the nature of the phenomenon. SUMMARIZING REMARKS
Because deteriorated spectra are seldom observed with hand-ground preparations, it might seem preferable to forego the practical convenience of the mechanical vibrator and resort to hand grinding in the routine preparation of potassium bromide disks. However, there is the problem of polymorphism to consider, and frequently, though not invariably, the vibrator technique helps to eliminate ambiguities arising from this cause. With this in mind, the authors adopted the following routine procedure for the preparation of potassium bromide disks of steroids. The steroid (2 mg.) and potassium bromide (400 mg.) are weighed succcssively into the capsule of the vibrator and vibrated with an agate ball for
1.5 minutes. The material is then transferred to the die, which is evacuated and the po\Tder is pressed a t 7 tons per sq. inch for a minimum of 3 minutes, after which the pressure and vacuum are released and the pellet is removed. The pellet is next heated a t 10.5' for a minimum of 5 minutes. If it remains clear, its spectrum is determined. If it becomes opaque during the heat treatment, the disk is reground by hand, using a mortar and pestle, the resultant powder is repressed and the spectrum of the new disk is accepted for characterization of the compound.
E. R., Jones, R. X., "Infrared Absorption Spectra of Steroids. An Atlas." Interscience. iVeF
mi& and 'Hormones:" Vol.
ACKNOWLEDGMENT
The author wishes to thank T. F. Gallagher and R. Norman Jones for helpful discussion and Beate B. Spiegel for technical assistance. LITERATURE CITED
(1j Barker, S. A , , Bourne, E. J., STTeigel, H.. Whiffen. D. H.. Chemistru & Industry 1956, 318. ' (2) Dobriner, K., Katzenellenbogen,
RECEIVEDfor review July 16, 1966. Accepted December 31, 1956. Investigation supported by a grant from the American Cancer Society and a research grant (C-2367) from the National Cancer Institute, National Institutes of Health, U. S. Public Health Service.
Infrared Spectra of Organic Azides EUGENE LIEBER Department o f Chemistry, De Paul University, Chicago, 111.
C. N. RAMACHANDRA RAO, T. S. CHAO,' and C. W. W. HOFFMAN Department o f Chemistry, Purdue University, Iafayette, lnd.
,The infrared spectra of a series of ten organic azides, the substituents of which covered the gamut of electropositive to electronegative, were studied to determine the range of frequencies where the strong asymmetric vibration of the azido group was likely to occur. The data show the NS asymmetric vibration to be in the region of 21 14 to 2083 cm.-l and confirm the constancy of this frequency, practically independent of the environmental structure. It appears that this absorption can normally be expected within the range of 2 1 7 0 to 2080 cm.-l This corresponds to approximately 0.2 micron in wave length. It is therefore still sufficiently characteristic to make it important for recognition of this group.
T
azido group, -S3,ran be identified by the strong ?;EN asymmetric stretching absorption which occurs with great consistency close to HE
1 Present address, Archer-Daniels Midland Co., Minneapolis, Minn.
916
ANALYTICAL CHEMISTRY
2130 em.-' The corresponding symmetric stretching is at considerably lower frequency and is not only much weaker, but also appears to be more variable in position. Accordingly, it appears to be of relatively little value for analytical use. The spectrum of hydrazoic acid has been examined by Eyster (9), who assigned the band at 2141 em.-' to the S=?s asymmetric vibration and that at 1269 to the corresponding symmetric mode. Methyl azide has been studied (IO) ; the corresponding bands in this case are a t 2141 and 1351 em.-' Azides as a group have been systematically studied by Sheinker and Syrkin (18) who examined the Raman spectra of sodium azide and the infrared spectra of 12 azides. They found a strong band in all cases in the range 2167 to 2080 em.-' and a second weaker one in the range 1343 to 1177 em.-' I n accordance with the earlier work, these were assigned to the asymmetric and symmetric vibrations, respectively. confirmation of this was obtained by Boyer (2) and Lieber, Levering, and Patterson ( I d ) , the latter repeating earlier work on sodium
azide (17) and examining five other organic azides not previously studied. They reported a relatively strong band in all cases in the range of 2151 to 2128 cm.-l, with a second weaker and more variable band near 1282 em.-' Accordingly, i t seemed probable that Sheinker and Syrkin (18) had quoted a wider range for the asymmetrical vibration than is likely to be found in normal practice. I n order to reevaluate this latter point, the infrared spectra of a series of alkyl, alicyclic, and aromatic azides \Tere studied. C O M P O U N D S USED IN STUDY
Table I lists the compounds used in this study, their physical properties, and the methods used, I n a search of the literature on the preparation of organic azides, i t was found that, in some cases, different values for the physical constants were given. T h e situation for benzyl azide is summarized in Table 11. A plot of log p vs.l/T showed that the value for the boiling point obtained for benzyl azide in this research agrees fairly d l with those given by most other investigators,
Table 1.
RK3, R n-Butyl n-Decyl Benzyl Cyclopent yl Phenvl p-Tory1 p-Bromopheny 1 p-Nitrophenyl m-Chlorophenyl o-Chloropheny 1
Table II.
c.
Boiling Points Reported for Benzyl Azide
64 78-78.5
Mm. Hg
M.P.,
n Lo 1.4192 1,4425 1 ,5373 1,4616 1.5598 1.5521 1.6127
c.
, .
.. 20 74
49-50;l. 2 4510.85
B.P., O
Organic Azides
B.P., c./ Mm. Hg 711225 6710.65 78-78.5112 72/77 41-42/5 55-56)4.5 6912.1
determined at a different pressure, its purity was established by elemental analysis. The data obtained are summarized below : Calcd. for CsH4BrN8:C, 36.40; H, 2.02; Br, 40.36. Found: C, 36.35; H, 2.27; Br, 40.51.
This research
whereas the value given by Moulin (14) does not. The refractive index agrees with that, of Moulin ( 1 4 , ng 1.5380, and of Philip (16), n$ 1.5341, assuming a straight-line relationship between temperature and refractive index over that range. I n the case of chlorophenyl azides, the comparison of physical properties obtained in this research nith that reported (19) is sumrnarized in Table 111. In view of the situation summarized in Table 111, the purities of o- and m-chlorophenyl azides obtained for this research were established by elemental analysis.
Table 111.
ArN3, Ar = o-Chlorophenyl nz-Chlorophenyl
Properties of
0-
The properties of the other organic azides used in this research and summarized in Table I are in agreement with the values previously reported in the literature.
INFRARED SPECTROSCOPY
The infrared absorption spectra were obtained on a Perkin-Elmer spectrometer Model 21, which was calibrated with polystyrene as a standard. Repetition of the infrared spectrum of sodium azide gave bands a t approximately the wave length previously reported (12). The infrared spectra of the series of organic azides are summarized in Table IV. Each measurement reported in Table IV was repeated at least twice.
and rn-Chlorophenyl Azides
Spauschus and Scott B.p., 'C./hlm. Hg ny 58-60/1.2 1.5855 49-51/0,7 1.5787
Calcd. for CsHaCINa:C, 46.92; H, 2.62; C1, 23.09; N, 27.39. Found: for o-chlorophenyl azide, C, 47.03; H, 2.61; C1, 23.00; N, 27.43; for m-chlorophenyl azide, C, 46.97; H, 2.69; C1, 23.01; N, 27.47. Dimroth and Pfister (7) have reported 105" at 10 mm. and 20" as the boiling and melting points of p-bromophenyl azide, while Spauschus and Scott (19) have reported 50" to 60" at 0.9 mm., a n d 1.6106 for the boiling point and ng for the same compound. As t h e boiling point of the p-bromophenyl azide prepared for this research was
This Research B.p., C./Mm. Hg ng 45/0.085 1.5878 49-50/1.2 1.5806 O
Table IV. Infrared Spectra of Organic Azides X3 AsymS, Sym-
RS,, R n-Butyl n-Decyl Benzyl Cyclopentyl Phenyl p-Tolyl p-Bromophenyl p-Nitrophenyl m-Chlorophenyl o-Chlorophenyl
metric, Cm.-l 2083 2092 2088 2083 2114 2092 2110 2114 2096 2088
( 4 , 11) (11)
(14) ( 3 , 11) (13) (8)
1,5806 1.5878
Reference
3 12
Reference
metric, Cm.-' 1256 1256 1256 1256 1287 1261 1287 1285 1288 1297
DISCUSSION
Bellamy (1) in discussing the lvork of Sheinker and Syrkin (18) felt that these investigators quoted a wider range, 2167 to 2080 em.-', for the asymmetric vibration than was likely to be found in normal practice, basing this assumption upon the work of Lieber, Levering, and Patterson (12). However, a careful study of Sheinker and Sgrkin's work (18) in comparison with that of Lieber, Levering, and Patterson (12), will show that this assumption is not valid. Although Lieber, Levering, and Patterson (12) shorved only a range of 31 wave numbers for the five azides studied, the environmental structures associated with the azido group were very nearly the same; the investigations of Sheinker and Syrkin (18), for 12 organic azides, covered a more representative range of electropositive and electronegative environmental groups, for which they obtained a difference of 87 wave numbers. Accordingly, the present study was a n effort to obtain a n additional answer to the question raised by Bellamy (1). Table IV shows that for a good spread of electropositive and electronegative environmental groups the range in this research for the N3 asymmetric band was only 31 wave numbers -namely, from 2114 to 2083 em.-' This does not entirely vitiate the observations of Sheinker and Syrkin (18); however, i t supports the assertion of Bellamy (1) and confirms the rather astonishing and interesting fact that the strong N1 asymmetric band is fairly constant regardless of its environmental situation. The widest range thus far reported is that of Sheinker and Syrkin (18), but this still represents a difference of only approximately 0.2-micron wave length. This insensitivity of the N3 asymmetric frequency is well documented by all investigators who have studied this problem, as well as the present research summarized in Table IV. On the other hand, the present study appears to be in disagreement regarding the variability of the N3 symmetric band. Table IV shows a rather interesting constancy, the range being only 41 wave numbers in VOL. 29, NO. 6, JUNE 1957
917
contrast to 166 wave numbers reported by Sheinker and Syrkin for approximately the same range of environmental changes. To the structural diagnostician this latter point is probably not too important, because reliance is placed upon the asymmetric band for the recognition of the azido group. Accordingly, if the range of 2170 to 2080 cm.-l be accepted for the iY3 asymmetric vibration likely to be found in normal practice, it is still sufficiently characteristic and intense to be important in recognition of this group. ACKNOWLEDGMENT
The authors are indebted to the spectroscopy laboratories of De Paul and Purdue Universities for assistance in taking the spectra and to the Office of Kava1 Research for a grant that made this study possible. The niicroanalyses are by the Galbraith Microanalytical Laboratories.
LITERATURE CITED
(1) Bellamy, L. J., “Infrnred Spectra of Complex Nolecules,’’ p. 230, Methuen &! Co., London, 1954. (2) Boyer, J. H., J . Am. Chem. SOC.73, 5248 (1951). (3) Boyer, J. H., Canter, F. C., Hamer, J., Putney, R. IC., Ibid, 78, 325 (1956). Boyer, J. H., Hamer, J., Ibzd.,77, 951 (1955). Curtius, T., Darapsky, A . , J . prakt. Chem. 6 3 , (2), 432 (1901). Curtius, T., Ehrhardt, G., Ber. 5 5 , 1565 (1922). Dimroth. 0.. Pfister. I. R.. Patterson,’ L.’ J., ACiL. C I I E I I . 23, 1591 (1951). ~I
,
I
Lindsay, R. O., Allen, C. F. H., Org. Svntheses 22. 96 (1942). Plloulin, Fr.,‘ Helu. Chim. Acta 35, 167 (1952). Soelting, E.,llichel, O., Ber. 26, 90 (1892). Philip, J. C., J . Chem. SOC. 93. 918 (1908). Randall, H. M., Fo-rler, R. C., Fuson, S . , Dangl, J. R., “Infrared Determination of Organic Structures,” Van Sostrand, Sew l o r k , 1919. Sheinker, Y. AI , Syrkin, Y. K., I z c s t A k a d . .\*auk. 8.S.S.R. Ser. Tu.14, 178 (1950). Spnuechus, H. O., Scott, J. M., J . -4m Chem. SOC.73, ?08 (1951). Wohl, A , , Oesteilin, C , Ber. 33, 2741 (1900). I ~ E C E I Vfor E Drevien. September 19, 1956. -4wepted January 17, 1957. Study started by tlie senior author (EL.) at Purdue L;niver.sit,y and completed at De Paul University. All requests for additional
information and reprints should bc ad-. dressed t o him a t De Paul University.
Versatile Gas-Liquid Partition Chromatography Apparatus G. K. ASHBURY, A. J. DAVIES, and J. W. DRINKWATER Shell Research,
Ltd., Thornton Research Centre, Chester, England
b In building the chromatographic apparatus described, an attempt was made to remove as many as possible of the instrumental limitations of the technique and to devise equipment capable of incorporating future developments with a minimum of modification. The instrument comprises one recorder unit which i s connected as required to one of several cclumnfurnace units maintained in a stand-by condition. Provision was made for rapidly changing columns and column temperatures. To permit the extension of the range of the gas-liquid partition chromatography method to higher molecular weights, a hot wire thermal conductivity detector was constructed entirely from refractory materials. It i s capable of reliable operation at temperatures upward of 300’ C.
W
of gas-liquid partition chromatography was clearly enunciated by Martin and Synge (4) as early as 1941, the importance of their suggestion was not gen918
HILE THE PRINCIPLE
ANALYTICAL CHEMISTRY
erally recognized a t that time. Since 1952, however. when the first account of the use of the method appeared in James and Martin’s classic paper ( 3 ) describing the isolation and microestimation of the volatile fatty acids, progress in applying it has been extremely rapid. Gas-liquid partition chromatography is too new for a n y preferred form of equipment to have established itself. I n consequence, the range of choice open t o the designer of apparatus for carrying out the procedure is at present unusually wide. I n these circumstances it is to be expected that the various forms taken by the equipment will strongly reflect the differing requirements each was designed to meet. This paper gives an account of the line of development that has been taken a t Shell’s Thornton Research Centre. \J70rk on gas-liquid partition chromatography started early in 1953, but within a few months the urgent need t o build a special-purpose chromatograph for the nearby Shell chemical plant diverted much of the effort that would have been available for
instrument development. During the construction of this apparatus, assistance to the analysts was virtually confined to providing them with a series of thernial conductivity detector cells and they nere forced to work with makeshift equipment. Khile this situation was embarrassing at the time, two important benefits follon-ed from it. I n the first place, the construction and testing of the cheniical plant’s apparatus familiarized the instrument development team with the technique and gave them a realistic appreciation of the problems likely to be encountered in designing future equipment. Secondly, and even more important, the hiatus gave the analysts time to accumulate useful norking experience with gas-liquid partition chromatography and enabled them to provide a rewonably accurate forecast of the way they n-ould use the custombuilt apparatus they mere later to be provided with. Thornton Research Centre carries out applicational research for the Shell group outside the U.S.A. and Canada. I t s problems concern the manifold
