Kinetical and thermodynamical analysis of the reactivity of thiourea by association to Ca2+

We have carried out a computational study on the kinetics of the reaction between Ca2+ and TU. The most preferred product from the kinetical point of view is the Coulomb explosion yielding TU+ and Ca+. This observation totally agrees with the MS/MS spectra of [CaTU]2+ complex and complements the conclusions drawn from the analysis of the Potential Energy Surface (PES). Contrary to [CaTU]2+, the process with the highest yield in [CaU]+ is the release of NH3. This dissimilar reactivity of U and TU towards Ca2+ is attributed to the lowest ionization potential of thiourea with respect to that of urea.