Liquid acetonitrile

Muller L J, Vanden Bout D and Berg M 1991 Ultrafast Raman echoes in liquid acetonitrile Phys. Rev. Lett. 67 3700-3... 

Sometimes electrochemists are forced to construct electrochemical cells without water, e.g. if the analyte is water sensitive or merely insoluble. In these cases, we construct the cell with an organic solvent, the usual choice being the liquids acetonitrile, propylene carbonate (I), N,/V-dirrielhylformamide (DMF) or di-methylsulphoxide (DMSO), each of which is quite polar because of its high dielectric constant e. 

SOLVENT ANIONS AND ELECTRON LOCALIZATION IN LIQUID ACETONITRILE... 

Below, we consider a polar, negative-EAg liquid—acetonitrile—in which the dimer anion formation (because of the electron accessing low-lying ir orbitals) competes with... 

In liquid acetonitrile, there are two radical anions present shortly after the ionization event anion-1 that absorbs in the NIR (whose band is centered at 1.45 (im) and anion-2 that absorbs in the 400-800 nm region (whose band is centered at 500 nm) see Fig. 5a [46,53]. These two anions are in a rapid dynamic equilibrium (Fig. 5b) As the liquid is... 

Figure 5 (a) Typical end-of-pulse absorption spectra obtained in pulse radiolysis of room temperature liquid acetonitrile (7-nsec fwhm pulse of 20 MeV electrons). The 500-nm peak is from anion-2 (dimer radical anion) the 1450-nm peak is from anion-1 (cavity electron), (b) Energy diagram and sketches of anion-1 and anion-2 (see the text). 

Figure 6 Singly occupied molecular orbital (SOMO) of a propeller-like trimer radical anion of acetonitrile obtained using density functional theory. The structure was immersed in a polarizable dielectric continuum with the properties of liquid acetonitrile. Several surfaces (on the right) and midplane cuts (on the left) are shown. The SOMO has a diffuse halo that envelops the whole cluster within this halo, there is a more compact kernel that has nodes at the cavity center and on the molecules.

Figure 4. A comparison of SD influence spectra for a dipolar diatom in liquid acetonitrile. The left panel depicts the spectrum corresponding to a change in the solute-solvent LJ energy and the right panel to a change in electrostatic energy. The gray lines depict the subspectra due to the solute ant the solvent molecule with the largest influence coefficient. The results are from Ref". ...

It is well known that the v, band of liquid acetonitrile is significantly asymmetric due to an overlap of hot band transitions in the low frequency side. A study of gas phase rotation-vibration spectrum [19] showed that the hot band transition from the first exited state of the degenerated C-C = N bending v8 mode, v hl = v + v8 - vs, has its center at 4.944 cm 1 lower than that of the fundamental transition, v,. Also the presence of v,h2 = v, + 2v8 - 2v8 transition is expected. The careful study on the v band of liquid acetonitrile by Hashimoto et al [20] provided the reorientational and vibrational relaxation times of liquid acetonitrile molecule. They corrected the contribution by the hot band transition using the Boltzmann population law and approximated the v , v,hl, 2h2, and v, + v4 bands by Lorentzian curves. 

CH3CN (g). Thomsen15 and Lemoult,1 respectively, measured the heats of combustion of gaseous and of liquid acetonitrile, methylcyanide. Their data yield, for CH3CN (g), Q = —20.3 and —17.9, respectively. 

Figure 3.20 Longitudinal dielectric relaxation in room-temperature liquid acetonitrile. Depicted is a comparison between the longitudinal dipole (dashed line) and charge density...

Figure 9 The normalized vibrational friction felt by a range of diatomic solutes dissolved in liquid carbon dioxide and liquid acetonitrile (62). The solutes are meant to represent the nondipolar molecule Br2 itself and two bromine mimics differing only in the replacement of the bromine quadrupole by permanent dipoles of different strengths. The d5 solute has a dipole moment of 5.476 D and the d8 solute a dipole moment of 8.762 D. (The notation r/vv emphasizes the fact that only potential-energy contributions are included in the calculations centrifugal force terms are neglected.)...

The low-frequency feature in the reduced spectral density corresponds to the long-time tail of the intermolecular response function, which is often denoted the intermediate response in the OKE literature (15,51). In most liquids, this portion of the response appears to be exponential over a significant time scale. Why this portion of the response is exponential and what information the time scale of this exponential holds is still poorly understood. For this reason, we have performed detailed temperature-dependent studies of the intermediate relaxation in six symmetric-top liquids acetonitrile, acetonitrile-d3, benzene, carbon disulfide, chloroform, and methyl iodide (56). 

Figure 5 Vibrational spectra of neat liquid acetonitrile (ACN) (top) mid-IR spectrum (bottom) Stokes Raman spectrum using a conventional spectrometer (solid line). The dashed spectrum obtained with the ultrafast laser system has somewhat lower resolution (From Ref. [46].)...

Deak JC, Iwaki LK, Dlott DD. Vibrational energy relaxation of polyatomic molecules in liquids acetonitrile. J Phys Chem 1998 102 8193-8201. 

Figure 4. Partial pair-distribution functions gij(r) as computed from an RMC procedure in liquid acetonitrile for N-CH3 pairs (stars) and contributions firom the nearest n neighbors of a central molecule (full lines).

Willetts and Rice attempted to develop a continuum model (type II) to calculate the EFISH response of liquid acetonitrile. Their results were compared with accurate calculations and measurements of the hyperpolarizability of the isolated molecule and measured solution for two different cavity radii. One natural choice of cavity radius is based on the van der Waals radius of the compound and with this value of a the discrepancy between the gas and solution measurements is not resolved. A rather smaller value of a can be selected to give much better agreement. The arbitrariness of the choice of cavity radius places a serious limitation on the usefulness of the continuum theories and, in recent years, there has been a considerable effort to develop hyperpolarizability calculations based on discrete molecular simulations of liquid and solution structure. 

M. Schwartz and C. H. Wang. Temperature dependent study of Rayleigh wing scattering in liquid acetonitrile. Chem. Phys. Lett., 29 383-388 (1974). 

In the case of interaction between carbon black and acetonitrile the signal for molecules bound to the surface has the form of a singlet whose chemical shift does not depend on temperature and is equal to the chemical shift for liquid acetonitrile (Fig. 11, curve 3). Consequently, acetonitrile molecules interact weakly with basal graphite planes of the surface. The most probable mechanism in this case is dipole-dipole interaction with polar groups that are predominantly situated on end faces and structural defects of basal planes of graphite. 

It is well known that the v, band of liquid acetonitrile is significantly asymmetric due to overlap of hot band transitions in the low frequency side. From a study of gas phase rotation-vibration spectrum [16], the hot band transition from the first exited state of the degenerate C-C=N bending Vj, mode, v, = V, + Vg - Vg, has its center at 4.944 cm ... 

Grabuleda, X. Jaime, C. Kollman, P. A., Molecular dynamics simulation studies of liquid acetonitrile new six-site model,./. Comput. Chem. 2000, 21, 901-908... 

As one would expect the vibrational spectra of aprotic liquids are usually much simpler than those for protic liquids. Acetonitrile is an example of an aprotic solvent whose polar properties are due to the large dipole moment associated with the — C=N bond. The — C=N stretch at 2254 cm is a prominent feature... 

Bohm et used the PD charges of Cox and Williams in a molecular dynamics study of liquid acetonitrile. The model yielded good agreement with experimental data on the thermodynamics, structure, self diffusion coefficients, and reorientational correlation times of the liquid. Hirshfeld and Mirsky used a site multipole model for ethanedinitrile (cyanogen) their model includes up to... 

Finely powdered phosphorus pentasulfide (0.3 mol, 65 g) is suspended in 500 ml of dry (dried by shaking with 30 g of P205 and distilling the decanted liquid) acetonitrile. Subsequently 1.5 mol of dry DMF is added and the mixture is stirred for 45 min at 65 °C. The reaction is weakly exothermic. The supernatant liquid is decanted and the solid rinsed four times with small portions of acetonitrile. After addition of 30 g of phosphorus pentasulfide the operations are repeated. The decanted liquid and the rinsings are concentrated under reduced pressure and the remaining liquid distilled to give the thioformamide, b.p. 95 °C/12 mm, n 0 1.5698, in 80 % yield. 

---