Probing the Molecular Orientation of Methyl Isobutyl Carbinol at the Air–Water Interface
The molecular orientation of a branched and short-chained methyl isobutyl carbinol (MIBC) at the air–water interface was examined by sum frequency generation vibrational spectroscopy. The weak vibrational coupling model was spectroscopically validated and employed in developing the data analysis model of this multiple terminal methyl groups-containing structure. The exceptional frothability of MIBC was explained by its molecular orientation at the interface; MIBC was found to tilt at an average angle of 39o to the surface normal, exposing its hydrophobic region to the air medium. Interestingly, this orientation scheme is similar to the hydrogen bonded OH bonds of the interfacial water molecules.
KeywordsSum frequency generation Molecular orientation analysis Terminal methyl groups Air/water interface Weak vibrational coupling treatment
This research was supported under Australian Research Council’s Projects funding schemes (Projects LE0989675, DP1401089 and DP150100395). KN would like to acknowledge the contribution of the Southern African Systems Analysis Centre, the National Research Foundation and the Department of Science and Technology in South Africa as well as the International Institute for Applied System Analysis.
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