Ir Spectra of
Matrix Isolated Disulfur Monoxide Isotopes
chemisorbed and physisorbed molecules and, in particular, the proton exchange between adsorbed water and the OH groups originating from a very limited hydrolysis of the Na-X near-faujasite zeolite. At two-thirds of the maximum water content, the proton lifetime in the OH group is 2 X sec at room temperature. Here the correlation time assigned to the proton jumps is 4.6 X sec a t room temperature and full loading. The jump frequency in the CDsOH-H-Y pool of protons is thus about loo0 times larger than in the system studied in Resing. Since the hydrolysis of Na-X does not generate lattice OH groups with the high acidityz2 characterizing those shown by the OH stretching bands in Figures 1-3, this difference is not surprising.
Conclusions (1)In the Na-Y sieve, the proton relaxation mechanism of adsorbed methanol is ruled by a diffusional motion. The diffusion coefficient at full loading is about half that measured a t one-third filling. These coefficients are in the right order of magnitude as compared with those reported for other adsorbed species. (2) In the decationated sieve, the proton relaxation mechanism of adsorbed CD30H is probably ruled by a proton exchange with the acid surface OH groups. The protonexchange process does not appear to be first order. Acknowledgments. Many thanks are due to W. E. E. Stone and to P. G. Rouxhet for stimulating discussions.
1849
The help of W. E. E. Stone in the experimental part of this work has been deeply appreciated by P.S.
References and Notes (1) On leave of absence from the CSlC on a Juan March fellowship. (2) (a) K. T. Geodakya, A. V. Kiselev, and V. I. Lygin. Russ. J. Phys. Chem. (Engl. TlanSl.), 41, 227 (1967); (b) V. Bosacek and 2 . Tvarutzkova. Collect. Czech. Chem. Cornmun., 36, 551 (1971). (3) P. 0.Rouxhet and R . E. Sempels, Trans. Faraday SOC., 70, 2021 (1974). (4) M. I. Cruz, W. E. E. Stone, and J. J. Fripiat, J. phys. Chem., 76, 3078 (1972). ( 5 ) S. J. Seymour, M. I. Cruz, and J. J. Fripiat, J. Phys. Chem., 77, 2847 (1973). (6) H. N o h , B. Mayerbock. and G. Zundel. Surf. Sci., 33, 62 (1972). (7) E. G. Weidemann and G. Zundel, 2.Naturforsch.,.TeilA, 28, 236 (1973). (8) R. Janoschek, E. G. Weideman. H. Pfelffer. and G. Zundel. J. Am. Chem. SOC.,94, 2307 (1972). (9) H. A. Resing and I. S.Murday, Adv. Chem. Ser.. No. 121, 414 (1973). (10) N. N. Avgul, A. G. Bezuz, and 0. M. Dzhigit, Adv. Chem. Ser., No. 102, 184 (1971). (11) L. Lerot, W.D. Thesis, University of Louvain. 1974. (12) P. Salvador et al.. unpublished data. (13) G. T. Kern, Adv. Chem. Ser., No. 121, 219 (1973). (14) P. Jacobs, personnal communication. (15) M. A. Vannice, M. Boudart. and J. J. Fripiat. J. Catal., 17, 359 (1970). (16) J. L. Wite. A. N. Jelly, J. M. Andre, and J. J. Fripiat. Trans. Faraday Soc., 63,461 (1967). (17) M. I. Cruz. J. Andre, K. Verdinne, and J. J. Fripiat, An. Quim., 69, 895 (1973). (16) P. A. Jacobs and J. B. Uytteheven, J. Chem. SOC.,Faraday Trans. 7, 69, 373 (1973). (19) H. A. Resing. Adv. Mol. Rebxation Processes, 1, 109 (1967). (20) M. M. Mestdag, W. E. E. Stone, and J. J. Fripiat. submitted for publication in Trans. Faraday SOC. (21) H. A. Resing, J. Phys. Chem., 78, 1279 (1974). (22) H. A. Resing, personal communication.
Infrared Spectra of Matrix Isolated Disulfur Monoxide Isotopes Alfred 0. Hopkins, Francis P. Daly, and Chris W. Brown. hpaflment of Chemistry, University of Rhode Island, Kingston, Rhcde lsland 0288 7 (Received February 70. 7975) Publication costs assisted by the Petroleum Research Fund
Infrared spectra of natural abundance and isotopically enriched SZOmatrix isolated in Ar have been measured. The vibrational bands of s2S2160,32S21s0, 34s2160, 34S32S160,and 32S34S160 have been assigned, and the observed frequencies of these isotopes used to calculate the harmonic force constants of S20.
Introduction The species S20 has been found to be stable for short periods of time in the gas phase at low pressures, and it is thought to be an important species in photochemical, combustion, and electrical discharge reactions of sulfur and oxygen. Schenk and Steudel’ have shown that S20 is one of the products formed from the very reactive SO species (reacting with itself), and that S20 is a good indicator for the prior existence of SO. In early ~ o r k , ~,920 . 3 was incorrectly identified SO or (SO)2. Later, Myer and coworkers4s5 correctly identified S 2 0 by mass and infrared spectroscopy. Several years ago we initiated a program to measure vibrational spectra of all of the sulfur oxides6p7 and of small sulfur ~ p e c i e s .Since ~ , ~ ~S20 ~ is one of the more important sulfur oxides, we have measured the infrared spectra of
most of its isotopic species isolated in inert gas matrices, and determined its harmonic force constants.
Experimental Section Infrared spectra were measured on a Perkin-Elmer Model 521 infrared spectrometer, which was calibrated with water vapor and polyethylene.1° SzO was prepared by passing SOpAr mixtures through either a radiofrequency (5200 W a t 10 MHz) or a microwave ((60 W a t 2450 MHz) electrodeless discharge. The “hot” gaseous mixture was condensed onto a CsI substrate in a Cryotip cell a t 20°K;11 the discharge region and the substrate were separated by a pinhole (0.8 to 3.5 mm in diameter). The gas was deposited at the rate of 3-6 mmolhr. SO2 (Matheson) was vacuum distilled several times prior The Journal of Physical Chemistry, Vol. 79,No. 17. 7975
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A. 0. Hopkins, F. P. Daly, and C. W. Brown
TABLE I: Observed Frequencies and Assignments of Bands in the Spectra of the SZOIsotopesa Frequency, cm-‘
Pure SOz
SO2 (nat. abund) discharge
SO2 (50% 34S) discharge
s2
SO2
(90% ‘*o) discharge
Type of vibration
SO stretch SO stretch PI’ SO stretch SO stretch s3,s4 SO stretch P2‘ SO stretch p3 SO stretch P3’ SO stretch s5 p4 SO stretch SO stretch p4 ’ S1 SI Sl SS stretch s5 SS stretch SS stretch sZ,s3 SS stretch s4 SSO bending SI Sl SI SSO bending SZ,S, SSO bending s4 SSO bending s5 Assignments: PI and PI’ = site split components of 3zS1eOz;Pz’ = site split component of 34S1eOz; P3 and P3’ = site split components of 3zSlSO18O; P4 and Pq‘ = site split components of 32S180z; SI = 3 2 S ~ 1 6 0Sa~ ,= 34S32S1e0,S3 = 3zSs4S160, S, = s*Sz160, Sa = 3 2 S p O .
1156.2 1151.4 1145.7 1144.0 1138.6 1122.3 1118.3 1114.8 1100.0 1095.8 672 .O 670.9 662.8 652.9 382.0 379.3 376.6 371.1
Sl
Pl PI’
Pl
to being used and it was mixed with Ar (Matheson, 99.998%) by standard manometric procedures. SO2 enriched in ‘ 8 0 (-90%) was obtained from Miles Laboratories, whereas SO:!enriched in 34S(-50%) was generated by heating enriched rhombic sulfur (Oak Ridge National Laboratories) with excess oxygen at 310’ for 8 hr in a Pyrex tube fitted with a Teflon stopcock.
Sl,
SI
PI Pl’
a t 1122.3 and 1114.8 cm-’ for Sl60l8O (P3 and P39. Thus, we have two unassigned bands in the expected intensity ratio of -1O:l at 1114.8 and 1156.2 cm-l, which we assigned to S:!l80 and S2l6O, respectively. The assignments of the SS stretching and the bending modes are unambiguous; the strongest component in each region is due to S:,l80and the weaker one (which is a shoulder in the SS stretching region) is due to Szl60. Results and Discussion In the spectrum of discharged SO:!(-50% 34S) shown Infrared Spectra. Infrared spectra in the region of interFigure IC the SO stretching region is more complex. We expect to find bands due to 32S02,34S02, 32S20, 34S20, est of pure SO:!, discharged SO:!(natural abundance), discharged SO:, (-50% 34S),and discharged SO2 (90% l80) 34S32S0,and 32S34S0(all with l60).The bands ‘due to matrix isolated in Ar (Ark302 N 400 in all cases) are shown 32S02(PI and PI’) and the stronger site split components in Figure 1. The observed frequencies and assignments are of 34SO:,(P:,’) are observed as expected. However, this listed in Table I. Interfering bands due to SO:, appear only leaves only two unassigned bands, 1156.2 and 1144.0 cm-l, for the four isotopic species of S20. To resolve this problem in the SO stretching region. In an Ar matrix the band due we calculated the force constants (see the section on force to the SO2 symmetric stretching vibration appears as a strong doublet (PI and PI’) due to site ~ p l i t t i n g ; the ~ ~ . ~ ~constants) for the two S20 isotopic species whose frequencies could be clearly assigned, i.e., 32S2160and 32S2180,and weaker band observed at -1139 cm-l is assigned to the used these force constants to predict the frequencies of the stronger of the site split components of 34S02 (in a natural SO stretching vibrations of the other 34-isotopic species of abundance sample the ratio of 32Sto 34Sis -25:l). S20. As a result, we found that 32S20 (SI) and 34S32S0 (S:!) In the spectrum of discharged SO2 (natural abundance) had the same SO stretching frequency (1156.2 cm-l), and shown in Figure I b relatively strong new bands appear at that 32S34SO ($3) and 34S20(S4)had the same frequency 1156.2, 672.0, and 382.0 cm-l. Previously, bands at 1165, (1144.0 cm-l), i.e., the mass of the terminal sulfur atom 679, and 388 cm-l were assigned to 32S2160by Blukis and does not affect the SO stretching frequency. We tried other Myers;5 the first band is due to the SO stretching vibration, possible assignments, but the calculated frequencies difthe second to the SS stretching vibration, and the third to fered considerably from the observed frequencies. the bending vibration. The assignments in the S-S stretching and in the bendIn the spectrum of discharged SO:! (90% 180)in Figure ing regions for 5096 34S enriched S20 were straightforward. Id, the SO stretching region is rather complex. We might bands were observed in each region; the band at the anticipate finding bands for Sl8O2, S1601s0, Sl60:!, S Z ~ ~ O Three , highest frequency was assigned to 32S20, the one at the and S:,l60 (all with 32S); however, the predicted ratio of next highest to 32S34SO and 34S32S0, and the one at the S180:!:S160180:S1602is -80:9:1. Thus, we would not expect lowest frequency to 34S20. The dual assignment of the cento see bands due to Sl60z,whereas we would expect to find tral band in each region is confirmed by the relative intentwo pairs of bands for SlSO:, and S1601s0 in the ratio of sities of -1:2:1 for the three bands. -9:l. Two pairs of bands with appropriate intensities are Force Constants. A normal coordinate analysis was perfound a t 1100.0 and 1095.8 cm-’ for Sl8O:! (P4and P4’)and The J O U r M l
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Phplcel Chemistry, VOl. 79, NO. 17, 1975
1851
Ir Spectra of Matrix Isolated Dlsulfur Monoxide Isotopes
TABLE 11: Force Constants for SZOCalculated Using Frequencies from Five Isotopes Force constanta
0
8.249 0.002 0.151 0.004 -0.013 0.005 G O ,0 Kaa 4.430 0.002 Kss,a 0.242 0.002 Ka 1.408 0.001 OUnits: K s o , Kss, and K80,88in mdynes/A; K,,,, and Kss., in mdynes/radian; and K , in mdynes A/radian2. KSO
Ks0,as
SO, ( 5 0 X "S DISCHARGE
TABLE 111: Observed and Calculated Frequencies for the Isotopes of SzO
SO,(SO
x
'00
Isotope
Obsd frequency, cm-'
Calcd frequency , cm-'
1156.2 672.2 382.0 1114.8 670.9 371.1 1144.O 652.9 376.6 1144.0 662.8 379.3 1156.2 662.8 379.3
1156.4 672.3 382.1 1114.6 670.6 370.5 1144 .O 653.1 376.8 1144.1 662.8 379.4 1156.2 662.8 379.4
32s2160 32s 2 1 8 0
34~2160 It50
1100 F R E Q U E N C Y , CM-'
Infrared spectra of pure SO2 (natural abundance), SO2 (natural abundance) discharge products, SO2 (50% 34S) discharge products, and SO2 (90% leg)discharge products, Isolated in Ar matrices (Ar/S02 = 400 In all cases).
32~34~160
Flgure 1.
formed using the Wilson FG matrix method and the force constant adjustment computer program written by Scha~htschneider.'~ The following geometrical parameters were used in the calculation^:'^ rso = 1.4594 A, r,, = 1.8845 A, and L,,, = 118.08O. The three valence bond force constants for the squared terms in the potential energy expression (K,,, K,,, and K,) and the three for the cross terms (K,,,,, K , , , , and K,,,) were used in the analysis; the resulting force constants obtained using all five isotopes of S20 are given in Table 11. The observed and calculated frequencies are given in Table 111. The average error in frequency for the 15 frequencies is 0.2 cm-' or 0.03%, which strongly supports the reliability of the assignments. Conclusions Although assigning the bands of the isotopic species of S20 was not extraordinarily difficult, the process was much easier after we completed the normal coordinate analysis on the vibrations of 32S160 and 32S21s0, i.e., on the vibrations of the isotopes that could be assigned with a degree of certainty. This adds support to the use of normal coordinate analysis in assigning the vibrational bands of simple molecules. Knowledge of the force constants of S20 should now make it possible to assign the vibrational bands of other lower oxides of sulfur.
34~32~160
Acknowledrnent. Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for support of this research. Two of us (A.G.H. and F.P.D.) gratefully acknowledge financial aid in the form of NDEA Title IV Fellowships. References and Notes (1) P. W. Schenk and R . Steudel in "Inorganic Sulfur Chemistry", G. Nlckless, Ed., Elsevler, New York, N. Y., 1968, pp 367-418. (2) P. W. Schenk, 2.Anorg. AI@. Chem., 211, 150 (1953); Chem. i'., 67, 273 (1943). (3) A. V. Jones, J. Chem. Phys., 18, 1268 (1950). (4) D. J. Meschi and R. J. Myers, J. Am. Chem. Soc.. 78, 6220 (1956); J. Mol. Spechosc.,3, 405 (1959). (5) U. Blukis and R. J. Myers, J. Phys. Chem., 69, 1154 (1965). (8) A. G. Hopkins, S.-Y. Tang, and C. W. Brown, J. Am. Chem. Soc., 95, 3486 (1971). (7) A. 0. Hopklns and C. W. Brown. J. Chem. Phys., 62, 251 1 (1975). (8) I?.E. Berletta and C. W. Brown, J. Phys. Chem., 75,4059 (1971). (9) A. G. Hopkins and C. W. Brown, J. Chem. Phys., 62, 1598 (1975). (10) E. K. Plyk, A. Danti, L. R. Blaine, and E. D. Tdweli, J. Res. NaN. Bur. Stend., 64, 1 (1960). (11) Cryotip cell, Model AC-2L-110, Alr Products and Chemicals, Inc. (12) J. W. Hastie, R . H a w , and J. L. Margrave, J. horg. Nucl. Chem., 31, 281 (1989). (13) D. E. Mliliganand M. E. Jacox, J. Chem. Phys.. 55, 1003(1971). (14) J. H. SchachtschneMer, "Vibrational Analysis of Polyatomic Molecules VI". Shell Develooment Co.. Emerwille. Calif.. 1964. (15) E. Tiemann, J. nbeft, F. J. Lovas: and D.R.'Johnson, J. Chem. Phys., 60, 5000 (1974).
