| Abstract
| - In a pilot study of the dielectric constant of room-temperature ionic liquids, we use dielectric spectroscopyin the megahertz/gigahertz regime to determine the complex dielectric function of five 1-alkyl-3-methylimidazolium salts, from which the static dielectric constant ε is obtained by zero-frequency extrapolation.The results classify the salts as moderately polar solvents. The observed ε-values at 298.15 K fall between15.2 and 8.8, and ε decreases with increasing chain length of the alkyl residue of the cation. The anionsequence is trifluoromethylsulfonate > tetrafluoroborate ≈ tetrafluorophosphate. The results indicate markedlylower polarities than found by spectroscopy with polarity-sensitive solvatochromic dyes.
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