Solvent properties of piperidinium ionic liquids

Experimental studies were made in the range 298–338 K for four synthesized piperidinium ionic liquids containing an alkyl chain on the cation 1-methyl-1-propylpiperidinium, 1-methyl-1-butylpiperidinium, and 1-methyl-1-octylpiperidinium with anion bis(trifluoromethylnsulfonyl)imide or bis(pentafluoroethysulfonyl)imide, and for three newly synthesized piperidinium ionic liquids containing a functional group on the cation 1-methyl-1-(3-cyano-1-propyl)piperidinium, 1-methyl-1-(pent-4-en-1-yl)piperidinium, or 1-methyl-1-[4,5-bis(methylthio)-1-penthyl]piperidinium with anion bis(trifluoromethylsulfonyl)imide. The influence of alkyl-chain length and the influence of a functional group on the cation on polarity and on three Kamlet-Taft parameters were investigated. The Kamlet-Taft parameters obtained are hydrogen-bond acidity α, hydrogen-bond basicity β, and dipolarity/polarizability π*.

• Piperidinium ionic liquids were synthesized to investigate polarity and Kamlet-Taft parameters.
• Alkyl-chain length on the cation has an influence on polarity and Kamlet-Taft parameters.
• An increase in the alkyl-chain length on the cation gives a small decrease in polarity.