Influence des substituants sur la basicité de pyridines en milieu apolaire

The frequency ν(OH … N) of methanol complexes with substituted pyridines appears to be a sensitive detector of substituent effects on the basicity of pyridines in an apolar medium. The coefficients ρI and ρR, which respond to I and R effects and which are obtained from the Taft–Ehrenson equation, agree with those found for the pKa of pyridinium ions for the three substitution positions. Those values which are observed to diverge are explained by the much greater electron attracting power of the azonium group compared to that of the aza group. [Journal translation]