Rates of N-H proton exchange for 1 and 2 were determined (a) by analysis of line-shape changes of H2O solutions at pH 8-11 and (b) by analysis of the slow spectral changes of D2O solutions observed at pD 2-6. The exchange reaction is OH- catalyzed over the whole pH range investigated. However, H2O catalysis contributes to the observed rate at pH <3. For 3, in which the β-carbon atom is the asymmetric center, rates of base-catalyzed C-H proton exchange and of inversion were found to be comparable. © 1969, American Chemical Society. All rights reserved.