RECHECKING OF THE EQUILIBRIUM GAS-PHASE BASICITY SCALE FOR LOW-BASICITY COMPOUNDS USING FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE SPECTROMETRY

Fourier transform ion cyclotron resonance (FT-ICR) spectrometry was used to study and recheck the proton transfer equilibria for a large number of low basicity compounds, particularly those which are less basic than H2O. The data obtained were used for the construction of a continuous scale of the relative gas-phase basicities between H2S and SO2F2. The present results are compared with the results obtained by McMahon and coworkers using ICR spectrometry and high-pressure mass spectrometric (HPMS) techniques, Satisfactory agreement is found with the existing ICR spectrometric data, The results, however, show unexplained variances with earlier and recent HPMS results that are also not internally self consistent. The substituent effects for some families of low-basicity compounds (nitriles, carbonyl compounds, ethers and some others) are discussed.