2084
J. Pbys. Cbem. 1980, 8 4 , 2084-2085
HCECCH~OHand CX3CH20Has evidenced by a study of coupling between 6(OH) and bending CH2vibrations." References and Notes I
2886
.
H
D
(1) H. Jeziorowski, H. Knozinger, W. Meye, and H. D. Muller, J . Cbem. Soc., Faraday Trans. 1 , 69, 1744 (1973). (2) H. Knozinger and B. Stubner, J . Pbys. Chem., 82, 1526 (1978). (3) J. C. Lavalley, ThBse, Caen, 1969; 0. Saur, J. C. Lavalley, and R. Romanet, C . R . Acad. Sci. Paris, Ser. B , 269, 816 (1969). (4) A. Allan, D. C. McKean, J. P. Perchard, and M. L. Josh, Spectrochim. Acta, Part A , 27, 1409 (1971). (5) H. P. Hamlow, S. Okuda, and N. Nakagawa, Tetrahedron Lett., 37, 2553 (1964). (6) E. Taillandier, Thbse, Park, 1970: J. Derouault, J. Le Calve, and M. T. Forel, Spectrocblm. Acta, Part A , 28, 359 (1972). (7) J. Derouault, Thbse, Bordeaux, 1971. (8) V. I. Yakerson, L. I. Lafer, V. Ya. Danyushevskll, and A. M. Rublnshteln, Izv. Akad. Nauk SSSR, Kbim., 10, 2246 (1967). (9) J. C. Lavalley and J. Caillod, J . Cbim. fbys., 77, 373 (1980). (10) J. Derouault, T. Driembowska, and M. T. Forel, J. Mol. Struct., 47, 59 (1978); Spectrocbim. Acta, Part A , 35, 773 (1979). (11) J. Travert, J. C. Lavalley and 0. Saur, to be submmed for publication. (12) J. Travert, 0. Saur, A. Janin, and J. C. Lavalley, J. Mol. Struct., 33, 265 (1976).
D
2956
Flgure 1. IR spectra of CD30CDJ,i (2800-3100-~m-~ range) (a)in CCI, solution, (b) coordinated to AICI, (L = AICI,), and (c) chemisorbed on y-alumina activated at 870 K.
Professor Knozinger agrees with this comment. ERA 824 Structure et Mactivh5 des Esp6ces Adsorbees Laboratoire de Spectrocbimie I.S.M.R.A., Universit6 de Caen 14032 Caen Cedex, France
TABLE I: v(CH) Wavenumbers of Some Alcohols and Their Corresponding Alkoxide Species Formed on r-Al,O, CD,HOH CD,CDHOH CC1,CDHOH
In CCI,, ref 12.
alcohola
alkoxide
-2965 sh 2920 -2940 sh 2898 2964 2921
2960b 2930b -2925 shc 288!jC 2965' 2900'
Reference 9.
Received: October 18, 1979
' Reference 11.
pmol g-l of CD30CD2Honto y-A1203produces a band pair at 3015 (very weak) and 2956 cm-' (with a shoulder on the high-frequency flank). The most relevant feature is the strong shift of u(CH) modes which allows us to use CD3OCD2H as a very suitable probe molecule to study the Lewis acidity of catalytic oxide surface^.^ Similarity between spectra of CD30CD2H coordinated to AlC13 and adsorbed onto A1203 (Figure 1) clearly shows that coordinative adsorption occurs on alumina. Alcohols. Recently, Derouault et al.,'O studying CH30H complexation with BF3, showed that the CH stretching modes are also observed at wavenumbers greater than those of free methanol. On the other hand, we have found that adsorbed v(CH) wavenumbers of alkoxide species formed when alcohols are adsorbed onto y-alumina generally shifted to lower values as compared with those of the corresponding alcohol in CC1, solution (Table I). Note that use of undeuterated alcohols does not lead to such clear shifts owing to the fact that 4CH) fundamentals are in Fermi resonance with 26(CH2)and 2w(CH2)overtones." By analogy with the present results on u(CH) vibrations of ethers and alcohols, one would conclude that the reduction of v(CD2) frequencies of (CH3)&HCD20H adsorbed onto alumina2points to a dissociative chemisorption of isobutyl alcohol rather than a coordinative adsorption. However, the possibility of coordinative chemisorption is not ruled out as a precursor state. In fact, it is difficult to predict u(CH) vibrations of species like R\
Jean-Claude Lavalley Jack Calllod Joseiie Traveri
0 .' ,H
I 0:
AI
as both effects (coordination and dissociation) affect u(CH) vibrations of the RO group in opposite directions. Note that fully dissociated species are observed in the case of This article not subject to U S . Copyright.
Irreversible Reaction of Nltromethane at Elevated Pressure and Temperature
Sir: Nitromethane was chosen as a model compound for a study of the effects on secondary explosives of high pressures and high temperatures similar to those in shock waves. A reaction has been observed when nitromethane is subjected to pressures of 50 kbar and temperatures of 150 "C. The product is dark in color and ranges from a viscous liquid to a powdery solid depending on reaction conditions. The reaction is completely irreversible; the product is thermally stable, persists at ambient conditions for at least several weeks, and appears to be insoluble in common organic solvents, water, and dilute acids. Figure 1illustrates a typical infrared spectrum of the final product at ambient conditions compared to the spectrum of nitromethane. Although infrared spectra of the product indicate a very simple molecular structure, a satisfactory identification has not been made. Attempts to obtain corroborating information by mass spectrometry and Raman spectroscopy have been unsuccessful to date. The primary impediment in identification is the minute amount (
