Acetonitrile frequency shifts

A useful way of analyzing this data is to compute the frequency shifts on going from the gas phase to acetonitrile solution ... 

Sclutlcn The geometry optimization reveals that the structure of formaldehyde in cyclohexane is essentially the same as it is in acetonitrile. Here are the predicted frequency shifts with respect to the gas phase for the two media ... 

System Gas Phase Calc. Exp. Acetonitrile Calc. Exp. Frequency Shift Calc. Exp. ... 

Obviously, this shift implies the self-association of DMSO. Further frequency shifts to even lower wave numbers (1050-1000 cm " ) are observed in both aprotic polar and protic solvents. In aprotic solvents such as acetonitrile and nitromethane, the association probably takes place between the S—O bond of DMSO and the —C=N or the —NOz group in the molecules by dipole-dipole interaction as shown in Scheme 331,32. Moreover, the stretching frequency for the S—O bond shifts to 1051 cm 1 in CHC13 and to 1010-1000 cm -1 in the presence of phenol in benzene or in aqueous solution33. These large frequency shifts are explained by the formation of hydrogen bonds between the oxygen atom in the S—O bond and the proton in the solvents. Thus, it has been... 

Table 5.9 Average Coordination Number for Acetonitrile to the Metal Cation and Frequency Shift of the V2 Band ( —C=N stretch) from IR Spectra of Metal Perchlorate Solutions in Acetonitrile [36]...

Carbon djoxide adsorbed on platinum in acetonitrile has a maximum at 2342 cm. Since the frequency shifts (compared to gas phase CO ) are very small, CO is probably physisorbed. It has been reported that adsorption of CO2 on platinum at anodic potentials involves chemisorbed CO (39). However, such a chemisorbed CO was not observed at cathodic potentials on platinum in acetonitrile. 

Figure 17.2.9 Resonance Raman spectra of TCNQ and electrogenerated TCNQ , which was coulometrically produced by reduction at —0.10 V V5. SCE. Initially, TCNQ was present at 10.9 mM in acetonitrile containing 0.1 M tetra-n-butylammonium perchlorate. Excitation wavelengths are indicated. Abscissa shows frequency shift with respect to excitation line. S denotes a normal Raman band of the solvent. [Reprinted with permission from D. L. Jeanmaire and R. P. Van Duyne, J. Am. Chem. Soc., 98, 4029 (1976). Copyright 1976, American Chemical Society.]...

Hydrogen cyanide, acrylonitrile, and acetonitrile adsorption on NaX and HY have been observed (20). Stronger interactions occur on the zeolite than on silica since the frequency shifts are greater. The nitriles interact with the cations in NaX and with the hydroxyl groups and dehydroxylated sites on HY zeolite. Acetonitrile, acetonitrile-d3, and benzonitrile have been adsorbed on various cation and HY zeolites (4). For acetonitrile, the C=N bond frequency is higher than that of the liquid phase and varies with cation, indicating that the adsorption of molecules is associated with the cation. A linear correlation is found between the cation electrostatic field and the CN bond frequency. 

If the current doisity is recorded together with the frequency shift, the charge change Ag in the redox cycle can be determined. The cyclic voltanunogram in a tetra-butyl-anunonium-perchlorate/acetonitrile electrolyte is shown in Figure 11.14. 

All the reported frequency shifts are reproducible 5% and have been normalised with respect to acetonitrile, the lowest molecular weight compound of the series. 

The DRIFT spectra of adsorbed acetonitrile-ds on the samples 3, 4, 4a (Figure 2) show the presence of strong Zn Lewis acid sites at the MOF surface. The C=N stretching vibrations frequency shift relative to the gas phase of acetonitiile-ds (2253 cm" ) is 45-55 cm" . 

It is interesting to observe the typical multiple character of out-of-plane modes of aromatic and hydrogensquarate fragments in solid-state IR spectra, which is observed in the cases of significant n-n interacted systems in the IR spectra of acetonitrile solutions. Moreover the discussed significant low-frequency shifting of the... 

Figure Bl.22.8. Sum-frequency generation (SFG) spectra in the C N stretching region from the air/aqueous acetonitrile interfaces of two solutions with different concentrations. The solid curve is the IR transmission spectrum of neat bulk CH CN, provided here for reference. The polar acetonitrile molecules adopt a specific orientation in the air/water interface with a tilt angle that changes with changing concentration, from 40° from the surface nonnal in dilute solutions (molar fractions less than 0.07) to 70° at higher concentrations. This change is manifested here by the shift in the C N stretching frequency seen by SFG [ ]. SFG is one of the very few teclnhques capable of probing liquid/gas, liquid/liquid, and even liquid/solid interfaces.

In the imido systems the n n transition is shifted to lower energy (518 nm) and markedly decreases in intensity. On the other hand, upon substitution of the anionic trans-ligands by acetonitrile the n->-n transition is found at 450 nm, shifting to 525 nm upon protonation. Moreover, the metal-N(nitrido) stretching frequency increases to 1016 cm From a chemical viewpoint it is important that the nitrido-nitrile complex can be... 

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