A co-crystal between benzene and ethane: a potential evaporite material for Saturn's moon Titan.

Using synchrotron X-ray powder diffraction, the structure of a co-crystal between benzene and ethane formed in situ at cryogenic conditions has been determined, and validated using dispersion-corrected density functional theory calculations. The structure comprises a lattice of benzene molecules hosting ethane molecules within channels. Similarity between the intermolecular interactions found in the co-crystal and in pure benzene indicate that the C-H⋯π network of benzene is maintained in the co-crystal, however, this expands to accommodate the guest ethane molecules.

Hydrogen Bonding between Water and Tetrahydrofuran Relevant to Clathrate Formation.

Tetrahydrofuran (THF) is well-known as a clathrate former as well as a promoter for gas hydrate formation. This work examines interactions between water and tetrahydrofuran via the effect on water's vibrational spectrum. Due to water's large oscillator strength in the hydrogen-bonded region, interactions are diagnosed by isolating small clusters in a transparent medium (carbon tetrachloride in this study).

Insights into hydrogen bonding via ice interfaces and isolated water.

Water in a confined environment has a combination of fewer available configurations and restricted mobility. Both affect the spectroscopic signature. In this work, the spectroscopic signature of water in confined environments is discussed in the context of competing models for condensed water: (1) as a system of intramolecular coupled molecules or (2) as a network with intermolecular dipole-dipole coupled O-H stretches.

Experimental study on the effect of ammonia on the phase behavior of tetrahydrofuran clathrates.

Clathrate hydrates, ice-like crystalline compounds in which small guest molecules are enclosed inside cages formed by tetrahedrally hydrogen-bonded water molecules, are naturally abundant on Earth and are generally expected to exist on icy celestial bodies. A prototypical example is Saturn's moon Titan, where dissociation of methane clathrates, a major crustal component, could contribute significantly to the replenishment of atmospheric methane. Ammonia is an important clathrate inhibiting agent that may be present (potentially at high concentrations) in Titan's interior.

Formation of a new benzene-ethane co-crystalline structure under cryogenic conditions.

We report the first experimental finding of a solid molecular complex between benzene and ethane, two small apolar hydrocarbons, at atmospheric pressure and cryogenic temperatures. Considerable amounts of ethane are found to be incorporated inside the benzene lattice upon the addition of liquid ethane onto solid benzene at 90-150 K, resulting in formation of a distinctive co-crystalline structure that can be detected via micro-Raman spectroscopy. Two new features characteristic of these co-crystals are observed in the Raman spectra at 2873 and 1455 cm(-1), which are red-shifted by 12 cm(-1) from the υ1 (a1g) and υ11 (eg) stretching modes of liquid ethane, respectively.

Water: a responsive small molecule.

Unique among small molecules, water forms a nearly tetrahedral yet flexible hydrogen-bond network. In addition to its flexibility, this network is dynamic: bonds are formed or broken on a picosecond time scale. These unique features make probing the local structure of water challenging.

Competitive binding of methanol and propane for water via matrix-isolation spectroscopy: implications for inhibition of clathrate nucleation.

Methanol is a well-known thermodynamic inhibitor of clathrate hydrate formation. The interactions responsible for the inhibition, however, are not well-identified. Propane is a relatively simple hydrocarbon that forms a clathrate hydrate under mild conditions.

Spectroscopic identification of water-propane interaction: implications for clathrate nucleation.

Propane is one of several hydrocarbons known to form a clathrate hydrate. To probe interactions leading to clathrate nucleation, the water-propane interaction is investigated in carbon tetrachloride with infrared spectroscopy. Isotopic substitution provides compelling evidence that the water-propane interaction occurs between the propane methylene hydrogen atoms and the water lone pair.