Hydrogenation of 6- or 8-R-substituted quinaldines [R=H, CH3, CH(CH3)2, C(CH3)3, or CF3] over platinum in trifluoroacetic acid gave higher yields (∼90%) of 5,6,7,8-tetrahydroderivatives than hydrogenation of the corresponding quinolines. ThepKa-values of 20 quinolines and quinaldines were determined by measuring the half-neutralization potentials in acetic anhydride. More basic quinolines gave higher yields of 5,6,7,8-tetrahydroproduct; exceptions are 6- and 8-methylquinoline and 8-tert. butylquinoline. Explanations for these observations are suggeste