1993 Volume 66 Issue 11 Pages 3326-3333
The reaction mechanisms of Mg (1S and 3P) atom and XH molecules (X = F, OH, NH2, Cl, SH, and PH2) were studied by ab initio molecular orbital methods. A localized molecular orbital centroid analysis along the reaction coordinate shows that the Mg(1S) atom insertion into the X–H bonds occurs through the pull–push mechanism. The activation barriers for the Mg(1S) atom insertion are approximately the same values for each groups (X = F and Cl, OH and SH, and NH2 and PH2).
For the Mg(3P) atom reactions with above six compounds, the hydrogen abstraction (produces MgH and H) and/or the exchange reaction (produces MgX and H) were studied. Both reactions of Mg(3P) atom are the same one with two-step mechanism. The first step is an electron transfer from a Mg atom into the X–H bonds, which corresponds the transition state. The activation barrier height of the reaction is explained by adiabatic electron affinity of the X–H bonds. The second step is the formation of the products (Mg–X+H or Mg–H+X), which is clarified by the difference of Mg–X and Mg–H bond energies.
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