High-level ab initio calculations have been carried out to investigate the preference of insertion with regards to the formation of adducts in the C+(2P) + silanoic acid reaction in the gas-phase. A total of ten local minima of the corresponding potential energy surface have been located and characterized. This has been done by calculating their relative stabilities at the G2 level and by analyzing their bonding characteristics by means of a topological analysis of their electron charge densities and their Laplacians. The global minimum correspond to the insertion of C+ into the Si=O double bond of silanoic acid, while the adducts to the Si=O group or to the hydroxyl group, as well as the insertions into the other bonds of the neutral lie much higher in energy. The most significant characteristics of the corresponding potential energy surface are very different from those found for the reaction between Si+ + HCOOH [1], where the global minimum corresponds to the insertion of the Si+ cation into the C-OH bond of the formic acid. Furthermore, while in the Si+ + HCOOH reaction the Si+ association to the carbonyl oxygen atom yields a complex which is only 4.9 kcal/mol less stable than the global minimum, for the C+ + HSiOOH reactions the association of C+ to the Si=O bond of the silanoic acid is 52.1 kcal/mol less favourable than the insertion into the same bond to yield the global minimum. In both cases we have found all the local minima investigated to lie bellow the reactants in energy. The distonic character of the products of both reaction processes is also analyzed.
This work has been partially supported by the D.G.I.C.Y.T Project No. PB93-0289-C02-01.