Determination of size of molecular clusters of ethanol by means of diffusion NMR and hydrodynamic calculations
(English)Manuscript (preprint) (Other academic)
Microscopic structure of ethanol in liquid state is characterized as dynamic equilibrium of hydrogen bonded clusters of different sizes and topologies. We have developed a novel method for determination of average size of the clusters that combines measurement of diffusion coefficient by means of PFG NMR technique and hydrodynamic simulations. The approach includes the use of HydroNMR [de la Torre 2000] for small molecules, which is attained here by the calibration procedure using dilute solution of tetramethylsilane. It is thus possible to correlate the experimentally determined apparent hydrodynamic radius of ethanol with calculated hydrodynamic radii of the modeled clusters of different sizes. We found that average size of the clusters in 0.16 M solution of ethanol in hexane ranges from monomer above 300 K to hexamer below 200 K. The clusters in the case of 0.44 M are generally slightly larger – from average size of dimer at 320 K to heptamer below 210 K.
ethanol, hydrogen bond, NMR, hydrodynamic simulation, density functional theory, diffusion coefficient, hydrodynamic radius
Research subject Physical Chemistry
IdentifiersURN: urn:nbn:se:su:diva-92899OAI: oai:DiVA.org:su-92899DiVA: diva2:643122