AB-INITIO CALCULATIONS ON ONOOH AND ONOO-

The geometry and electronic structure of peroxynitrous acid (O=NOOK) a nd peroxynitrite ion (O=NOO-) were studied at the as 6-31G* level. Th e cis-configuration of peroxynitrous acid was found to be more stable by 3.9 kJ/mol than the trans-form, whereas peroxynitrite is more stabl e by 4.6 kJ/mol in the trans-form. Calculations of the skew forms, whi ch are as defined by an angle of 90 degrees between the ONO/NOO planes , yield energies larger than those of the most stable forms of the aci d or anion by 51.4 and 68.1 kJ/mol, respectively, thus providing an es timate of the gas-phase energy barrier. The electronic structure is di scussed from the point of view of the reactivities and transformation processes of ONOOH and ONOO-. (C) 1993 John Wiley & Sons, Inc.