Infrared spectra of acetonitrile sorbed on porous glass

Abstract

Infrared spectra were recorded of acetonitrile sorbed on highly degassed porous glass as well as on silica and B-, Al-, and Zr-impregnated porous glass and silica. Most of the acetonitrile was weakly and reversibly adsorbed, becoming hydrogen-bonded to surface hydroxyls. A small amount of the adsorbate for~ned qeakly bound surface con~plexes with Al-and Zr-, but not with B-impurities.Canadian Journal of Chemistry, 48, 7 (1970) Introduction Roev, Filimonov, and Terenin (1) recorded infrared spectra of acetonitrile adsorbed on silica, porous glass, and on a silica-alumina catalyst and concluded that hydrogen bonds were formed between the acetonitrile molecules and the surface hydroxyls of the three solids. The weakly held acetonitrile could be desorbed easily. However, the spectrum of the silicaalumina catalyst, recorded after the hydrogenbonded acetonitrile had been removed, showed bands indicating the presence of an additional, more tightly bound surface species. The symmetrical C=N stretching absorption of these was shifted in a manner analogous to the C s N shifts found with acetonitrile -metal chloride complexes, leading Roev et al. to assume that specific adsorption centers possessing an electron-acceptor nature existed on the silica-alumina catalyst. Similar effects were not reported for acetonitrile on silica or on porous glass.

Adsorption Structure and Coverage-Dependent Orientation Analysis of Sub-Monolayer Acetonitrile on TiO2(110)

“…In the CN stretching region (see in Figure 4), the frequency of ν(CN) of CH 3 CN on Ti 5c sites at 100 K shows a ∼65 cm −1 blue shift compared to those of pure phase CH 3 CN 11−13 and vapor CH 3 CN on the solid surface. 14,15,49 This suggests that the first layer CH 3 CN was chemisorbed on Ti 5c sites at low temperature, which is consistent with the fact that the CN stretching frequency of CH 3 CN shifts to higher frequency upon bonding with electron-accepting centers. 19,22,49−51 The sum resonance of symmetric C−C stretching and symmetric CH 3 deformation is also termed as Fermi resonance in some reported works 17,50 because this combination band undergoes Fermi resonance with ν(CN).…”

“…This remains to be identified by temperature-dependent SFG measurements. In the CN stretching region (see in Figure ), the frequency of ν­(CN) of CH 3 CN on Ti 5c sites at 100 K shows a ∼65 cm –1 blue shift compared to those of pure phase CH 3 CN − and vapor CH 3 CN on the solid surface. ,, This suggests that the first layer CH 3 CN was chemisorbed on Ti 5c sites at low temperature, which is consistent with the fact that the CN stretching frequency of CH 3 CN shifts to higher frequency upon bonding with electron-accepting centers. ,,− The sum resonance of symmetric C–C stretching and symmetric CH 3 deformation is also termed as Fermi resonance in some reported works , because this combination band undergoes Fermi resonance with ν­(CN). Hence, the relatively higher intensity of the ν SR mode observed in this work results from this Fermi resonance, and its disappearance in the reported SFG spectra of vapor CH 3 CN on metal-oxide surfaces , is possibly due to the large frequency difference between ν­(CN) and the sum frequency of the symmetric C–C stretching and the symmetric CH 3 deformation, which induces weak intensities by the low enhancement of the poor Fermi resonance.…”

Adsorption and surface reactions of acetonitrile on AlO-supported noble metal catalysts

“…Thus, we are strongly convinced that the bands at 2357 and 2329 cm À1 are due to n(CN) in acetonitrile adsorbed on very strong Lewis acid (Al 3+ ) sites and on strong Lewis acid (Al 3+ ) sites, respectively. Formerly these bands were detected at lower frequencies (2332 and 2300 cm À1 ) on Al 2 O 3 [12]; it should be mentioned, however, that the band at 2345 cm À1 had been attributed to a CH 3 CN-Al surface species [25]. The stability of the 2357 and 2329 cm À1 bands experienced in this study may strengthen our assignment, as these bands were observed with very low intensity even after the heat treatment at 673 K ( Fig.…”

On the Diffusion of Acetonitrile in Nanoscale Amorphous Silica Pores. Understanding Anisotropy and the Effects of Hydrogen Bonding

“…Mesoporous silica is widely studied for its potential use in a variety of applications while acetonitrile is an important organic solvent which also possesses spectral features that can be used to probe its properties in porous oxides. As such, acetonitrile in mesoporous silica has been studied both experimentally − and computationally − as has acetonitrile at planar silica interfaces. , …”

“…We have previously simulated the linear infrared CN stretching spectrum of acetonitrile in silica pores and have found that the spectrum is not sensitive to many changes in the liquid structure and dynamics induced by the confinement . However, the CN stretching mode frequency is shifted to higher frequencies upon hydrogen bonding providing a clear signature of molecules hydrogen-bonded to surface silanol groups in a pore. ,,, The localization of hydrogen-bonding sites at the surface suggests that nonlinear vibrational spectroscopy, which can probe spectral diffusion, may be sensitive to acetonitrile translational diffusion near the surface to the extent that it is related to hydrogen-bond making and breaking. It is thus interesting to examine acetonitrile diffusion and the molecular-level mechanisms involved.…”