Comparison of Minimal and Extended Basis Sets in Terms of Resonant Formulas. Application to 1,3 Dipoles

The validity of weights of structural formulas derived from valence-bond wave functions is questionable, because these functions are, by necessity, calculated with minimal basis sets. To test this validity, we compare the structural weights, calculated in minimal and extended basis sets, for a series of 1,3 dipoles, one of the rare systems for which some kind of extended basis valence-bond function can be obtained. Both basis sets provide results in good agreement for the dipoles having no outer oxygen. The relevance of the calculated structural weights to chemical reactivity is discussed.