IR-visible sum frequency generation (SFG) vibrational spectroscopy was employed to investigate the microscopic structures at interfaces between room temperature ionic liquids and various molecular liquids. The alkyl chain of the [C_nmim]~+ polar cation orients toward the hydrophobic (CC1_4) phase at the CCl_4/ionic liquid interface, while it orients randomly or points towards the ionic liquid phase at a D_2O/ionic liquid interface. An anomalous enhancement in the amplitude of the CD3 asymmetric stretching mode is observed at a butanol/ionic liquid interface, suggesting the formation of a hydrophobic layer which consists of the alkyl chains of the butanol and the [C_n mim]~+ cation.
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