S. Tauro, E. Coutinho
Nov 17, 2000
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Influential Citations
13
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Journal
Journal of Molecular Structure-theochem
Abstract
Abstract The compound 7-amino-4-hydroxy-3-[(4-methoxy-2-sulfophenyl)azo]-2-naphthalene sulfonic acid is an intermediate in the preparation of water-soluble dyes that are used for dyeing and printing of textiles in fast shades. The geometries and energies of the ground and transition states of tautomers of this molecule were computed at the PM3 level of theory. The results show that there are two stable conformations of the trans azo configuration and two unique cis azo forms. However, the trans azo forms are more stable than the cis . Among the five possible tautomers, it is seen that the order of stability runs I (azo)> II (hydrazone)≫ III a ∼ III b > IV . Transition states computed for the various equilibria show that the azo–hydrazone ( I ⇋ II ) equilibrium is the most favored with the lowest energy. The results from this study closely parallel those reported earlier by us for a related molecule, from which it is concluded that the position of the amino group in these molecules has very little influence on their structure and dynamics.