STRUCTURAL-PROPERTIES AND POTENTIAL REACTIVITY OF SUBSTITUTED 3-AROYLDITHIOCARBAZATES

A series of substituted 3-aroyldithiocarbazates has been synthesized a nd studied. The corresponding acid dissociation constants have been de termined potentiometrically. Semiempirical PM3 molecular orbital calcu lations suggest the existence of several tautomeric forms of the compo unds. Geometrical parameters, proton affinities. and static reactivity indices have been examined. Structural properties and protonation sit es are well described by calculations. The strong correlations between the pK(a) values and the Hammett sigma constants as well as the N(3) calculated proton affinities indicate that the N(3) atom is the most p robable protonation site. The thermodynamics of the protonation proces s are mainly controlled by HOMO-LUMO rather than electrostatic interac tions. According to PM3 results, 3-aroyldithiocarbazic acid should be quite stable in the gas phase, while a mechanism for its decomposition in solution is proposed.