Quantum chemical studies on structure, conformation and isomerization of nitroso, nitro substituted benzene and 1,3-cyclopentadiene

The molecular structure, conformational stability and isomerization of nitroso, nitro substituted benzene and 1,3-cyclopentadiene in gas phase have been investigated using ab initio and density functional theory methods. The molecular geometries and energetics of possible conformers were obtained by employing MP2, B3LYP and B3PW91 levels of theory implementing 6-31G* basis set. The relative stabilities of the conformations were evaluated from the energy differences of the structure. Chemical hardness (η) and chemical potential (μ) were calculated at HF/6-31G* level of theory for all the positional and geometrical isomers to study the maximum hardness principle. Each optimized structure has been tested against the imaginary frequencies at MP2/6-31G* level of theory in order to be sure they are located at energy minimum.