STRUCTURE AND ENERGETICS OF NAPHTHOFURAZAN OXIDES AND THEIR O-DINITROSO ISOMERS - A COMPUTATIONAL STUDY

The equilibrium between annelated furoxans (6, 7, 12, 16, 18, 22, 24) and the isomeric dinitroso derivatives (9, 10, 11, 13, 14, 15, 17, 19, 20, 21, 23, 25) has been investigated theoretically by semiempirical( AM1, PM3) and ab initio methods (MP2/6-31G1/6-31G* and RHF/6-31G*). I n order to describe the equilibria correctly it is necessary to includ e electron correlation. For both 1,2- and 2,3-dinitrosonaphthalene, se veral conformers exist as minima on the potential energy surface (PES) . Calculations of the energy difference between [1,2,5]thiadiazolo[3,4 -e]benzoxadiazole-1-oxide (26) and 3-oxide (27) are in qualitative agr eement with experimental data.