On the important role played by polarization functions in calculations involving hypervalent molecules

It is shown that special care must be taken to choose a basis set with an a ppropriate number of polarization functions when studying processes involvi ng several hypervalent molecules, each with some particular atom exhibiting different Lewis structures. The reaction between 1,3 butadiene and sulfur dioxide rendering either sultines or sulfolenes, depending on the experimen tal conditions, serves as an illustration. (C) 2000 Elsevier Science B.V. A ll rights reserved.