Interconversion of five isomeric tautomers of formohydroxamic acid via intramolecular proton transfer has been examined by ab initio theoretical calculation. The transfer potential surfaces, the global isomeric structures, and the transition geometries of intramolecular proton transfer were determined by the MP2/6-31+G** level of calculation. The energy was further analyzed by a single point calculation, MP2/6-31++G**//MP2/6-31+G**, and the use of G2 theory. Not counting the unstable charge separating species, the order of stability of these tautomers calculated at the HF level was 1E > 1Z > 2Z > 2E, and it shifted to 1Z > 1E > 2Z > 2E at the MP2 level, where 1Z and 1E are keto forms, while 2Z and 2E are iminol forms. Further investigation using G2 theory redirects the order to be 1Z > 2Z > 1E > 2E. The strength of the intramolecular hydrogen bond and the effect of dipole moment are the two major factors to dominate the acidity of formohydroxamic acid. Judging from the transition barrier of intramolecular proton-transfer we believe that formohydroxamic acid in dissociating proton in the gas phase is an N-acid.

We performed ab initio electronic structure calculations on the structures and energetics of the mixed hyperalkaliated hydrogen oxides Li 4 OH, Li 3 NaOH, and Li 2 Na 2 OH. Five equilibrium geometries exist for each complex of Li 4 OH and Li 3 NaOH, and seven minima were located for Li 2 Na 2 OH. The calculated dissociation energies for the possible dissociation pathways are all endothermic. The global minimum structures of the three complexes have C 2V symmetry and contain a hydrogen-bridged, Li-H-Li, three-centered skeleton. We also investigated the charge redistribution within these complexes in their ionic forms. The energetic factors governing the construction of the equilibrium structures and their bonding properties are analyzed.

1997 theory, structure theory, structure C 1000 -003Ab initio Calculations on the Structures and Energetics of Li4OH, Li3NaOH, and Li2Na2OH Isomers.-Ab initio calculations show the existence of five equilibrium geometries for each complex of Li4OH and Li3NaOH and locate seven minima for Li2Na2OH. The global minimum structures have C2v symmetry and contain a Li-H-Li hydrogen-bridged three-centered skeleton. -(LEE, C.-L.; SHEU, M.-J.; SHIE, Y.-S.; WU, D.-H.; HO, J.-J.; J. Phys.