Interaction of Acetonitrile with Water-Ice: An Infrared Spectroscopic Study

Abstract

Interaction of water-ice and acetonitrile has been studied at low temperatures in their codeposited mixtures, in ultrahigh vacuum conditions. They interact strongly at low temperatures (in the temperature range of 40−110 K), which was confirmed from the new features manifested in the reflection absorption infrared spectra of the mixtures. This interaction was attributed to strong hydrogen bonding which weakens upon warming as the acetonitrile molecules phase segregate from water-ice. Complete phase separation was observed at 130 K prior to desorption of acetonitrile from the water-ice matrix. Such a hydrogen-bonded structure is not observed when both the molecular solids are deposited as water on acetonitrile or acetonitrile on water overlayers. A quantitative analysis shows that in a 1:1 codeposited mixture, more than 50% acetonitrile molecules are hydrogen bonded with water-ice at low temperatures (40−110 K).

Facile Crystallization of Ice Ih via Formaldehyde Hydrate in Ultrahigh Vacuum under Cryogenic Conditions

“…These shoulders gradually disappeared as the ice mixture was heated beyond 90 K, eventually becoming a broad peak, which is the characteristic feature of ASW. Similar H-bonded features and their disappearance with heating were also observed with the acetonitrile and water mixture . Here, the breaking of H-bonds occurs due to heating, and they are completely broken at 90 K, the crystallization temperature of formaldehyde.…”

Clathrate hydrates in interstellar environment

“…Experiments were conducted in an ultrahigh vacuum instrument (base pressure ∼10 −10 mbar), which was described elsewhere (20, 21). Briefly, the instrument consists of a UHV chamber made of stainless steel, equipped with RAIR spectroscopy and TPD mass spectrometry.…”

Qualitative observation of reversible phase change in astrochemical ethanethiol ices using infrared spectroscopy

“…Amorphous ice is, in general, more porous than crystalline ices. In a mixture of molecular ices, for example, in the case of acetonitrile-water mixture, when acetonitrile turns crystalline well before water crystallization temperature, the water molecules are segregated from the mixture [10]. Therefore amorphous ice, due to its higher porosity, relative to crystalline ice, acts as a trap for other molecules which in turn strongly influences the chemical reactivity of the ice at a given temperature.…”