Combining nanosecond and millisecond time scale techniques: determination of thermodynamic and kinetic data of primary alkyl amine cation radicals.

Abstract

Primary alkyl amines are one of the most commonly used and effective reagents in CO2 capture. Most of the amines used for CO2 capture are recycled, but a minor portion of the amines are degraded after one electron oxidation process, leading to highly toxic substances. The combination of the complementary information obtained from photoinduced electron transfer (flash photolysis) and heterogeneous electron transfer (electrochemistry) appears to be very attractive to fully characterize the electron transfer reaction mechanism of reactive species in general, as well as for determining important thermodynamic properties, such as standard potentials (E°) or pKa values. It is particularly difficult to determine these crucial data accurately in the cases of alkyl primary amines. Hence, in this manuscript we focus on the establishment of the several alkyl primary amines oxidation mechanism in organic aprotic solvents. In order to achieve this, this work combines information provided by flash photolysis (nanosecond), cyclic voltammetry (millisecond), and digital simulation (nanomile-second). Moreover, the accuracy of the E° values calculated using the nanosecond equilibrium method allows not only revising them, but also estimating new important thermodynamic data concerning the bond dissociation energies (BDEs) of ammonium cations (N(+)-H) and of the amine cation radicals (α-C-H), as well as their corresponding pKa values.