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Persistent URL http://purl.org/net/epubs/work/46695101
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Record Id 46695101
Title Co-crystals, Salts and Ionic Co-crystals of Ethanol and Ammonia
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Abstract Compounds of ethanol and ammonia have been known for over a century but no structural characterisation has been carried out. Solid crystalline specimens of molecular ethanol mono-ammoniate and ethanol hemi-ammoniate were prepared by flash freezing of stoichiometric liquids in liquid nitrogen followed by annealing between 175 K and 195 K. High-resolution neutron powder diffraction measurements were used to determine the complete structures of the two compounds. Both are triclinic (P-1, Z = 2): ethanol mono-ammoniate is characterised by linear tapes of four-sided hydrogen-bonded rings, which extend along the crystal’s b-axis; ethanol hemi-ammoniate’s structure is defined by sheets (in the crystal’s a – b plane) comprised of two different types of four- and six-sided H-bonded rings. Measurements collected as a function of temperature provide a precise determination of the thermal expansion of the two ethanol ammoniates and of solid deutero-ammonia. Density Functional Theory calculations yield insights into the response of each structure to hydrostatic stress, including a proton transfer to form either wholly ionic ammonium ethoxide crystals or ionic co-crystals of ethanol ammonium ethoxide. The switch from molecular to ionic co-crystal in ethanol hemi-ammoniate may occur on cooling at ambient pressure, with kinetic frustration due to the low temperature of the transition. Proton transfer at ambient pressure, or at modest impact shock pressures, suggests that there may be extensive ammonium salt formation amongst compounds of the simplest alcohols. This may represent an important additional mechanism for the generation of NH4+ spectroscopic signatures in remotely sensed data from interstellar, cometary and planetary ices.
Organisation ISIS , ISIS-HRPD , STFC
Keywords
Funding Information
Related Research Object(s): 10.5286/ISIS.E.95699847 , 50387189
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Language English (EN)
Type Details URI(s) Local file(s) Year
Journal Article ACS Earth and Space Chemistry 4, no. 9 (2020): 1612-1625. doi:10.1021/acsearthspacechem.0c00155 2020