Rate constants for the gas-phase reaction of OH with amines: Tert-butyl amine, 2,2,2-trifluoroethyl amine, and 1,4-diazabicyclo[2.2.2]octane

The title compounds were selected to test the current predictions of OH reaction rate constants. The reactions are studied employing flash photolysis/resonance fluorescence in 130 mbar He at room temperature and up to 420 K. Experimental difficulties were encountered due to the polar and hygroscopic properties of the compounds. The rate constants obtained at 298 K, 12, 0.9, and 22 · 10^-12 cm³/s for tert-Butyl amine (TBA), 2,2,2-Trifluoroethyl amine (TFEA), and 1.4-Diazabicyclo[2.2.2]octane (DABCO®), respectively, are much lower (up to a factor > 20) than calculated with the incremental system devised by Atkinson, indicating that electronic and steric effects should not be neglected. Activation energies are slightly negative for TBA and DABCO and some +450 K for TFEA. The reactivity of TFEA was also determined (as 1.2 · 10^-12cm³/s) relative to a set of hydrocarbons employing continuous photolysis of H₂O₂ in a glass chamber.