Thermochemistry of gaseous manganese oxides and hydroxides

The reactive vaporization of MnO(c) in the presence of O2 and H2O/D2O has been studied by effusion-beam mass spectrometry, and the new species MnO2, MnOH, Mn(OH)2, and MnO(OH) have been identified. The identities of the hydroxides were confirmed from deuterium isotopic substitution. Reaction enthalpies and standard enthalpies of formation have been derived from equilibrium measurements, yielding the ΔfH°298 values for the gaseous species MnO2, −17.6; MnOH, 0.1; Mn(OH)2, −95.9; and MnO(OH), −41.1, all in kcal mol−1. For use in the analysis, thermal functions were calculated from known or estimated molecular constants. Bond energies derived from the results fall in a logical and consistent sequence.