1H nuclear magnetic resonance studies of solutions of aromatic bases. Part I. Proton exchange in ethanol solutions of pyridines
Abstract
The overall rate of proton exchange in ethanol solutions of pyridine, γ-picoline, and 2,6-lutidine was measured by observation of the methylene proton lineshape as a function of concentration. The process obeys the empirical rate equation (i) where k1= 2·8 × 109 l mol–1 s–1 for pyridine, 4·3 × 108 for γ-picoline, and 0·7 × 108 for 2,6-lutidine and k2 is approximately constant at 6 × 108 s–1. The first term refers to the symmetrical exchange reaction (ii). Rate =k1[BH+][B]+k2[BH+] mol l–1 s–1(i), BH++ EtOH*+ B ⇌ B + HOEt + H*B+(ii)
The second term may reflect exchange catalysed by EtO–.