Thermodynamic and infrared studies of substituted quinoline N-oxides with bis-(2,4-pentanedionato)oxovanadium(IV)

Abstract

The use of bis-(2,4-pentanedionato)oxovanadium(IV) as a reference Lewis acid has been investigated with 4- and 6-substituted quinoline N-oxides as bases. A correlation has been obtained between the enthalpies of reaction for the acid–base interaction and σ_PyNO for the 4-substituted quinoline N-oxides. A correlation has also been obtained for the shift in the vanadium–vanadyl oxygen stretching frequency of the reference acid (Δ_{v = 0}) and σ_PyNO. Enthalpies of reaction for the interaction of the reference acid and the 4-substituted quinoline N-oxides have been correlated with Δ_v=o. The 4-substituted quinoline and pyridine N-oxides are compared. Frequency-shift and enthalpy data are reported for the interaction of 6-substituted quinoline N-oxides and the reference acid.