Determination of the Lewis acidity of amide–AlCl3 based ionic liquid analogues by combined in situ IR titration and NMR methods

Abstract

A combinatorial method to determine both acidic strength and acidic amount of each Lewis acid site in amide–AlCl₃ based ionic liquid (IL) analogues was developed by the combination of in situ IR titration and NMR analysis. ³¹P NMR was used to distinguish effectively the acidic strength of each Lewis acid site in the amide–AlCl₃ based IL analogues. Nitrobenzene was used as a molecular probe to measure the total Lewis acidic amount of the amide–AlCl₃ based IL analogues by in situ IR titration. The acidic amount of each Lewis acid site in the amide–AlCl₃ based IL analogues was calculated with the assistance of ²⁷Al NMR analysis.