GEOMETRICAL CONSEQUENCES OF RESONANCE-ASSISTED INTRAMOLECULAR HYDROGEN-BOND FORMATION FROM AB-INITIO MO CALCULATIONS ON 2-NITRORESORCINOL

Ab initio orbital calculations on phenol, nitrobenzene, and 2-nitroresorcinol have been performed with the GAUSSIAN 92 series of programs. Initial RHF/6-31G* and RHF/6-31G** optimizations were followed by second-order Moller-Plesset MP2(FC)/6-31G* optimizations. The general geometrical features of these molecules, and, in particular, the characteristic changes as going from phenol to 2-nitroresorcinol and from nitrobenzene to 2-nitroresorcinol are in good agreement with recent gas-phase electron diffraction studies and with the notion of resonance-assisted intramolecular hydrogen-bond formation in 2-nitroresorcinol.