Interaction of Acetonitrile with Alcohols at Cryogenic Temperatures

Abstract

Temperature-dependent interaction of acetonitrile with methanol and ethanol, as codeposited and sequentially deposited films, was studied in the 10–130 K window, in ultra high vacuum. Films in the range of 50–100 monolayers were investigated using temperature-dependent reflection–absorption infrared spectroscopy (RAIRS), Cs+ ion scattering mass spectrometry, and temperature-programmed desorption (TPD). Acetonitrile interacts with methanol and ethanol through intermolecular hydrogen bonding. When a codeposited system was annealed, acetonitrile underwent a phase segregation at 110 K, and large changes in the infrared spectrum were observed. The OH stretching of methanol gave two peaks characteristic of the change to the α-phase of methanol, while ethanol gave three peaks at the same temperature. The surface composition of the systems probed by 40 eV Cs+ scattering showed that both the alcohols and the acetonitrile were of equal intensity below 110 K, while above 110 K the intensity of the latter went down substantially. We find that the presence of acetonitrile does not allow ethanol to undergo complete phase transition prior to desorption, while methanol could do so. This behavior is explained on the basis of the size, extent of hydrogen bonding, and phase transition temperature, of the two alcohols. Additional peaks in the hydroxyl region observed in alcohols in the 110–130 K window may be used as a signature of the presence of acetonitrile mixed with alcohol, especially ethanol, and hence this may be used in observational studies of such molecular environments.

Thermal Processing and Interactions of Ethyl Formate in Model Astrophysical Ices Containing Water and Ethanol

“…Given the observed shift in the COC vibration and the minor shift in the CO vibration, it is expected that ethyl formate interacts with ethanol via the lone pairs on the two oxygen atoms, as it does with water. Similar interactions have previously been seen for acetonitrile with ethanol …”

“…Similar interactions have previously been seen for acetonitrile with ethanol. 57 Annealing the ethyl formate/ethanol mixture to higher temperatures does not lead to crystallization of the ethyl formate ice, as expected given the mixing in the ice (Figure S3). However, annealing 50 L m of ethyl formate adsorbed on top of a layer of ethanol does lead to crystallization to the same phase as initially seen when pure ethyl formate is heated to 100 K, as seen in Figure S3 in the Supporting Information.…”

Rapid crystallization of amorphous solid water by porosity induction

“…The set-up has been used extensively to study molecular solids. 6,7,12,49,50 UHV was maintained by using several turbomolecular pumps backed by oil-free diaphragm pumps (Pfeiffer Vacuum). Pressure was monitored by a Bayard-Alpert gauge (Pfeiffer Vacuum), controlled by a MaxiGauge controller (Pfeiffer, Model TPG 256 A).…”

Correspondence between Spectral-Derived and Viscosity-Derived Local Composition in Binary Liquid Mixtures Having Specific Interactions with Preferential Solvation Theory

“…Spectroscopic techniques (UV–vis, IR, X-ray) can provide qualitative and sometimes quantitative characterization of complex molecule populations in binary solvent mixtures. ,− However, these techniques are cumbersome when probing the hydration shell for many different types of solvent systems due to differences in solvent volatility or requirements in conditions such as temperature or concentration. − Therefore, in this work, the objective was to propose a viscosity model based on the preferential solvation theory that allows estimation of local composition from bulk viscosity data and does not require complicated experimental or data reduction procedures.…”