tion measurements with modified adsorbents should provide a means to separate resonance effects from inductive effects. The data in Figures 1 and 2 illustrate several other interesting points. In the case of biphenyl, only one ring appears to be able to interact as a pi-electron system with the adsorbent because its retention is approximately that expected from its up value. Previous studies indicate that the two aryl rings are not coplanar (67); this could account for the second aryl ring not interacting with the sorbent as a pi system. In contrast, nitrobenzene has a much higher retention than the substituent constant would predict. Evidently the additional pi system of the nitro group is in a position to interact with (6) 0. Bataiansen, Acta Chem. Scand., 3, 408 (1949). (7) F. J. Adrain, J. Clzem. Phys., 28, 608 (1958).
the surface. Naphthalene shows a decreased retention relative to the aromatic line even though the number of pi-electrons has increased. This may be a steric effect limiting the approach of the pi system to the adsorbent surface, or it may be because naphthalene has a smaller pi-electron density than benzene. Research in progress on other adsorbents and modifying materials may provide the means for measuring additional specific functional effects for organic molecules. RECEIVED for review February 15, 1968. Accepted May 6, 1968. Work supported by the US. Atomic Energy Commission under Contract No. AT-(1 1-1)-34, Project No. 45, and by an Environmental Sciences Predoctoral Fellowship (US. Public Health Service)to D.J.B.
Conversion of Water to Carbon Dioxide with N,N’-Ca rbonyIdiim idazole James C. Warf Jet Propulsion Laboratory, California Institute of Technology, Pasadena, Calif,
THE VIGOROUS
REACTION of N,N’-carbonyldiimidazole with water to form carbon dioxide and imidazole has been known for some time ( I ) . In some current studies involving incorporation of oxygen-18 into microorganisms, an improved means of analysis for oxygen-18 was developed. Combustion of the microorganisms to carbon dioxide and water left the oxygen-18 divided between the two compounds ; conversion of all the oxygen-18 to carbon dioxide was desired for mass spectrometric analysis. The use of N,N’ - carbonyldiimidazole seemed promising for this purpose, despite the fact that attempts to employ this reaction analytically were not previously successful ( 2 ) owing to the formation of a protective coating of imidazole on the solid reagent.
EXPERIMENTAL
Reagents. The N,N’-carbonyldiimidazole was purchased from the J. T. Baker Chemical Co. The solvents, White Label quality from Eastman Organic Chemicals, were dried with Drierite and distilled at atmospheric pressure; the first 10% of the distillates was rejected. Oxygen-18 water was supplied by the Oak Ridge National Laboratories. USE OF SOLIDN,N’-CARBONYLDIIMIDAZOLE. Small columns containing 100 mg of the powdered reagent became inactivated and converted only a part of the water to carbon dioxide, as mentioned above. Tests showed, however, that a few milligrams of water, stored several hours in the presence of an excess of N,N’-carbonyldiimidazole, were completely converted to carbon dioxide. No residual water vapor could be detected mass spectrometrically. A method employing a solution of the reagent was expected to be rapid and to make the conversion practical. SOLVENTS FOR N,N’-CARBONYLDIIMIDAZOLE. A Solvent for the reagent was needed which had negligible vapor pressure at room temperature and which had appreciable solubility for water (so as to promote reaction). The first solvent tested (1) H. A. Staab, Angew. Clzem., 68, 754 (1956). (2) H. Malissa and E. Pell, “Microchemical Techniques,” N. D. Cheronis, Ed., Interscience, New York, 1961, p 378.
1370
ANALYTICAL CHEMISTRY
was diglyme [bis (Zmethoxyethyl) ether], but even without water, the mass spectrum showed many peaks, including those corresponding to mass numbers 44 and 46, thus making diglyme useless as a solvent. Other solvents tested were Carbitol acetate [2-(2-ethoxyethoxy)-ethyl acetate], quinoline, isoquinoline, and adiponitrile. None of these, when employed with N,N’-carbonyldiimidazole, gave extraneous mass spectrometric peaks, and all were suitable for the purpose. But only adiponitrile (bp 295 “C) seemed to form solutions which did not become discolored on storage. When the procedure given was followed, using 2 or 3 p1 of water, only carbon dioxide peaks were visible in the mass spectrometric tracing, with no water or other peaks. Apparatus and Procedure. The HzO or Hz0-C02 mixture from a combustion tube was carried by a stream of helium through a microbubbler containing 1.0 ml of a 10% solution of N,N’-carbonyldiimidazole in adiponitrile. The microbubbler was of 9-mm tubing and 10 cm long, and was packed with small glass beads. Vitron O-ring connections were employed. The COZ was finally trapped out in a liquid nitrogen bath, and the trap evacuated. A fresh portion of the adiponitrile solution was used for each run. The apparatus was preflushed with helium before use. A Consolidated Electrodynamics Corp. Model 103C instrument was employed in the mass spectrometric analyses. RESULTS
Analysis of Natural Water. Three analyses of ordinary water for by the procedure outlined gave the following results: 0.202, 0.200, and 0.204 atomic % I s 0 . The accepted natural abundance is 0.204 atomic % (3). In the calculations, correction was made for the l8Ocontributed to theCI601 8 0 by the N,N’-carbonyldiimidazole. Analysis of Enriched Water. A sample of Oak Ridge HZ1*0, specified as 8.6 atomic % l8Owas also analyzed in triplicate. This gave 8.36,8.60, and 8.43 atomic % I8O. (3) D. Samuel, “Oxygenases,” 0. Hayaishi, Ed., Academic Press, New York, 1962, p 32.
The mass spectrometer revealed the presence of small amounts (0.06 to 0.1 mole %) of C1802. The equivalent of this as c160180 was accommodated in the final computation. With a rich sample of H2180(55 atomic % the C 1 8 0 ~ amounted to 2.8 mole % of the total Con. The C180z evidently arises from the exchange of C16O17O with unreacted Hz180.
ACKNOWLEDGMENT
The mass spectrometric analyses were carried out by Maurice Frech. RECEIVED for review February 27, 1968. Accepted April 25, 1968.
Separation of Chlorostyrenes and Ethylbenzene/Xylenes Charles F. Raley and James W. Kaufman Physical Research Laboratory, The Dow Chemical Co., Midland, Mich. ORGANO-CLAYS have been previously discussed as chromatographic supports for the separation of various aromatics. The separation of ethylbenzene and the xylenes has received particular attention. Columns of Bentone-34 modified with diisodecyl phthalate ( I ) , silicone oil (2, 3), tricresyl phosphate, and dinonyl phthalate ( 2 ) have been described. In the present work, the separation of the isomeric monochlorostyrenes and ethylbenzene/xylenes using a column of Bentone-34 packing modified with bis-(phenoxyphenyl) ether (4P3E) was compared with the separations obtained using these other packings. The best separation of the xylenes was obtained with the Bentcne-34/dinonyl phthalate column. The separation of the six isomeric chlorostyrenes was best on the 4P3E-modified column.
Apparatus. The apparatus, using on-column injection, was constructed in this laboratory. It employed a Podbielniak Type 9981 thermal conductivity detector with Gow-Mac W filaments, and a Sargent Model S-72180-35 1 mV recorder. The columns were 12-foot X 3/16-in~h 0.d. stainless steel tubing (operating conditions shown in Table I) packed with the following: 10 pph Bentone-34; 5 % Bentone-34 and 5 % diisodecyl phthalate (DDP); 10 pph Bentone-34 and 10 pph silicone oil (DC-550); 10 pph Bentone-34 and 10 pph tricresyl phosphate (TCP); 10 pph Bentone-34 and 10 pph dinonyl phthalate (DNP). The columns of Bentone-34 and Bentone34/4P3E used 70-80 mesh Anakrom AS support; the last three were on 60-100 mesh Chromosorb W. The proportions of ingredients and types of support were chosen to duplicate those previously used. Column Preparation. The column was prepared in the usual fashion, by slurrying the support and liquid phase in benzene, and flashing off the volatiles. For example, to a ( 1 ) S. F. Spencer, ANAL.CHEM., 35, 592 (1963). (2) J. V. Mortirner and P. L. Gent, ibid.,36,754 (1964). (3) E. W. Cieplinski, ibid., 37, 1160 (1965).
Table I. Operating Conditions Chlorostyrenes Alkylbenzenes 150 170 250 50 0.3
v)
z 0
n v)
W K
K
EXPERIMENTAL
Column temp, "C Injection port temp, "C Detector temp, "C Helium flow, cc/min Sample size, p1
W
100 170 250 50 0.3
W 0
K
0 0
----hhL
L!
n
W
K
c
D.E
F
0 pph BENTONE-34 /IOpph DC-550
n
E
Adu
Lj
&C E F
0.G
3 pph BENTONE-34/lOpph TCP
O(AIR)
5
IO
15
20
25
TIME (MIN.)
Figure 1. Separation of chlorostyrenes solution of 1.25 grams of 4P3E (The Dow Chemical Co.) in approximately 100 ml of benzene was added 2.5 grams of Bentone-34 (National Lead Co.). After the suspension was stirred for 1 hour, 25 grams of Anakrom AS was added and thoroughly stirred. The benzene was flashed off using a rotating baffled flask attached to a Rinco Model VE-1000-B evaporator. The devolatilization was carried to 100 "C at 0.8 mm. A straight length of stainless steel tubing, 12 feet x 3/16 inch 0.d. was filled with this packing, plugged with glass wool and wound into a coil. The columns were conditioned at 150 "C for 12 hours before use. The packing of Bentone-34 and DDP was obtained from F&M Scientific Corp. under catalog No. LP14. DC-550 is the trademark of Dow Corning Corp. for a silicone oil containVOL. 40, NO. 8 , JULY 1968
0
1371
