Structure and dynamics of aqueous 2-propanol: a THz-TDS, NMR and neutron diffraction study
Collins, James HP
Holbrey, John D
Youngs, Tristan GA
Stitt, E Hugh
Physical Chemistry Chemical Physics
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McGregor, J., Li, R., Zeitler, A., D'Agostino, C., Collins, J. H., Mantle, M., Manyar, H., et al. (2015). Structure and dynamics of aqueous 2-propanol: a THz-TDS, NMR and neutron diffraction study. Physical Chemistry Chemical Physics, 17 30481-30491. https://doi.org/10.1039/C5CP01132A
Aqueous liquid mixtures, in particular, those involving amphiphilic species, play an important role in many physical, chemical and biological processes. Of particular interest are alcohol/water mixtures; however, the structural dynamics of such systems are still not fully understood. Herein, a combination of terahertz time-domain spectroscopy (THz-TDS) and NMR relaxation time analysis has been applied to investigate 2-propanol/water mixtures across the entire composition range; while neutron diffraction studies have been carried out at two specific concentrations. Excellent agreement is seen between the techniques with a maximum in both the relative absorption coefficient and the activation energy to molecular motion occurring at ∼90 mol% H2O. Furthermore, this is the same value at which well-established excess thermodynamic functions exhibit a maximum/minimum. Additionally, both neutron diffraction and THz-TDS have been used to provide estimates of the size of the hydration shell around 2-propanol in solution. Both methods determine that between 4 and 5 H2O molecules per 2-propanol are found in the 2-propanol/water clusters at 90 mol% H2O. Based on the acquired data, a description of the structure of 2-propanol/water across the composition range is presented.
The authors would like to acknowledge CASTech (EPSRC grant EP/G011397/1), RCUK Basic Technology Grant (EP/E048811/1), STFC for beamtime allocation (RB910286) and Jon Mitchell (Cambridge) for valuable discussions.
External DOI: https://doi.org/10.1039/C5CP01132A
This record's URL: https://www.repository.cam.ac.uk/handle/1810/253435
Attribution 2.0 UK: England & Wales
Licence URL: http://creativecommons.org/licenses/by/2.0/uk/
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