4420
C O M M U N I C A T I O N S TO THE E D I T O R
An Apparently Primary CH6+ Ion in the Mass Spectrum of 2-Methoxyethanol
Sir: We have observed the ion CHe+ in the mass spectrum of 2-methoxyethanol and have found that it is apparently a primary ion. This ion has been observed previously in the mass spectrometer,l-10 but to our knowledge, this is the first time it has been recognized either as a primary ion or in a system which does not include methane. We have identified this ion as part of a doublet appearing at m/e 17. I n a spectrum of 2-methoxyethanol (Fisher certified reagent) dried over anhydrous CaS04 run on a Consolidated Electrodynamics mass spectrometer Model 21-103C, we have observed this doublet, while in other samples dried with an excess of the CaS04 the lower mass peak (OH+) is diminished to a shoulder on the higher mass peak. Accurate determination of the mass of the latter peak was done by measuring the accelerating voltage for this peak and comparing it to the voltages for the known peaks at m / e 15, 16, 18, and 19. The results are given in Table I. The peak at m/e 17 is about 80% of the height of the CH4+ peak at m/e 16. Therefore, it could not be due to I3CH4+. Spectra were also run on a high-resolution Hitachi mass spectrometer, Model RMU-6D. In one of these, some NH3 was added. To the second was added a
small amount of CH3D. It was expected that NH3+ should appear about 65% of the distance from the OH+ to the CHS+. The mass difference between CH3Df and CHj+ is one part in 11,000, which is approximately the stated resolution for this instrument. The results are shown in Figures 1 and 2.
Table I : Determination of Exact Mass of m/e 17 Peak in the Mass Spectrum of Dry 2-Methoxyethanol Trial
Mass found
1
17.0435 17.0377 17.0434 17.0441 17.0337 17.0405
2 3 4 5 AV.
Expected masses‘: = 17.0386
OH+
= 17.0022;
0.0038 (av. dev.)
NH,+
= 17.0260;
CHs+
a Calculated on the basis of automatic weights in J. H. Beynon and A. E. Williams, “Mass and Abundance Tables for Use in Mass Spectrometry,” Elsevier Publishing Co., New York, N. Y., 1963, p. vii, and considering the mass of the electron.
Pressure dependence studies were made using the Consolidated instrument and measuring the pressure with a micromanometer. A typical set of data plotted as peak height vs. inlet pressure is shown in Figure 3. It can be seen that the relationship is linear.
(1) See the reviews by (a) C. E. Melton in “Mass Spectrometry of Organic Ions,” F. W. McLafferty, Ed., Academic Press, New York, N. Y., 1963, Chapter 2 ; (b) J. Durup, “Les Reactions Entre Ions Positifa et Molecules en Phase Gazeuse,” Gauthier-Villars, Paris, 1960, p. 20.
(2) A. Cassuto, Advan. iVass Xpectrometry, Proc. Conf., Bnd, Oxford, 1961, 2 , 296 (1963).
(3) G. R. Cook, J. A. R. Samson, and G. L.Weissler, U. S. Department of Commerce, Officeof Technical Services, P. B. Report 145,185 (1959).
(4) F. H. Field, J. L. Franklin, and M. 8. B. Munson, J. Am. Chem. Soc., 85, 3575 (1963).
I
Figure 1. High-resolution spectrum of the multiplet a t m/e 17 in 2-methoxyethanol with added ammonia.
The Journal of Physical Chemistry
(5) C. E. Melton and W. H. Hamill, J. Cham. Phys., 41, 1469 (1964). (6) M. 8. B. Munson, F. H. Field, and J. L. Franklin, J. Am. Chem. Soc., 85, 3584 (1963). (7) K. R. Ryan and J. H. Futrell, J. Chem. Phys., 4 2 , 824 (1965). (8) N. N. Tunitskii and S. E. Kupriyanov, Tr. Peraogo Vses. SoPeshch. po Radiatsion. Khim., Akad. Nauk SSSR,Otd. Khim. iVauk, Moscow, 7 (1958). (9) H. yon Koch, U. 5.Department of Commerce Accession NO.AD 603 091 (1964), Avail. CFSTI. (10) S. Wexler, J . Am. Chem. Soc., 85, 272 (1963).
4421
COMMUNICATIONS TO THE EDITOR
Acknowledgment. We wish to thank Mr. A. Struck of the Perkin-Elmer Corporation for obtaining some of the spectra mentioned in this communication. MICHIGAN STATEUNIVERSITY EASTLANSING, MICHIGAN
0 Ht
KERMITR. WAY MORLEYE. R U S S E L L ~ ~
RECEIVED AUGUST 30, 1965
Pulse Radiolysis of Fused Alkali Halides’
Figure 2. High-resolution spectrum of the multiplet a t m/e 17 in 2-methoxyethanol with a small amount of added methane&.
1 31.
d
/
I
I
0
1.0
2.0’ P,l& p
3.0
x
4.0
I
5.0
6.0
lo-%
Figure 3. Peak intensity us. the inlet pressure.
Isotopic studies to determine the mechanism of formation of this ion are in progress. (11) Department of Chemistry, Northern Illinois University, DeKalb, Ill. 60116.
Sir: The coloration of alkali halide crystals by ionizing radiation, by treatment with alkali metals, and by electrolysis, is well known. Coloration of alkali halides in the liquid state by solution of alkali metals or by electrolysis has often been reported2; however, coloration by ionizing radiation does not appear to have been studied. This communication reports some preliminary observations on colorakion of alkali halide melts using the pulse radiolysis technique. Two samples were used, one of pure KCl and the other an equimolar mixture of KC1 and KBr. Samples were prepared from single-crystal material supplied by the Harshaw Chemical Co. and were held in ampoules made from 13-mm. tubes of Suprasil high-purity fused silica. Ampoules were evacuated before sealing. During measurements, the sample temperatures were maintained a few degrees above their melting points in an oven with an aperture for the light path. The optical system consisted of a lamp passing white light through the center of the sample, through a monochromator, and to an 51 multiplier phototube whose output was suitably displayed on a dual-beam oscilloscope. MeasFrements could be made over the range 5000-1 1,000 A. Samples were irradiated by 4-psec. pulses of 30-Mev. electrons. The dose delivered was determined by a calorimetric method and was, typically, lo5 rads/pulse. With this arrangement, a moderate-to-strong absorption was observed to form during a pulse and to decay after a few microseconds. A typical oscilloscope trace is shown in Figure 1, curve A. A moderately intense radioluminescence was observed t o interfere with measurements of absorption. This luminescence could be measured independently by closing a shutter between the lamp and the sample; a typical oscilloscope trace is shown in curve B of Figure 1. The absorption (1) Research partially supported by the Air Force Cambridge Research Laboratories, Office of Aerospace Research, under Contract AFlQ(628)-2926. (2) See, for exnmple, M. A. Bredig in “Molten Salt Chemistry,’: M. Blander, Ed., John Wiley and Sons,Ino., New York, N. Y., 1964, p. 367.
Volume 69, Number 12 December 1966
