CRYSTALLOGRAPHIC AND PM3-COSMO SCF-MO STUDY OF THE STRUCTURE AND PROPERTIES OF ARYLOXY-THIAZINONES OR ARYLTHIO-THIAZINONES

The solid state structures of three para-substituted aryloxy- or arylt hio-thiazinone derivatives reveal that the conformation of 2 differs f rom 1 and 3 in the orientation of the Y-aryl bond, due in part to an u nusually strong C=O...H-C-S intermolecular interaction of r(O...H) 2.2 0 Angstrom present in 2. A search of the Cambridge crystal structure d atabase revealed relatively few other structures with similarly strong O...H-C interactions in which the common feature is the H-C-S structu ral unit. The observed reaction rate for aqueous hydrolysis of this se ries of compounds via attack of water at the C(2) position was found t o correlate with the energy of the highest unoccupied orbital correspo nding to sigma rather than pi character, but no feature in the wavefun ctions could be found which identified 2 as the most likely to form th e strongest O...H-C-S hydrogen bonding interaction in this series.