Ab initio calculations of the structure and conformations of 2,6-lutidine
Year: 1997
Authors: Porcinai S., Foggi P.
Autors Affiliation: LENS, Università di Fircnze, Largo Enrico Fermi 2, 1-50125 Firenze, Italy
Abstract: Ab initio molecular orbital calculations at the SCF level have been utilized to determine the structure and the electronic and vibrational properties of 2,G-lutidine (2,6-dimethyl-pyridine) in the ground electronic state. Comparative calculations have been perfomed on the parent molecule pyridine. Structure predictions of both molecules are in good agreement with experimental data. The most stable rotamer of 2,6-lutidine has C2l. symmetry with one of the C-H bonds of both the methyl groups lying in the plane of the aromatic ring and pointing in the opposite direction with respect to the nitrogen atom. This is the result of the minimization of eompetiting forces deriving from steric hindrance and electronic stabilization. Vibrational frequencies and oscillator strengths of C-H stretching in the fundamental region have been calculated for both pyridine and the most stable rotamer of 2,6-lutidine and compared to IR data obtained in pure liquids. The potential energy profile of the C-H bond in and out of plane has been investigated up to five times the equilibrium distance. The trend of the potential curves confirms that the C-H bond lying in the plane has a higher dissociation energy than that of the in-plane bonds as observed in experiments on vibrational overtones.
Journal/Review: IL NUOVO CIMENTO D
Volume: 19 (7) Pages from: 889 to: 900
KeyWords: Stretching overtone spectra; Vapor-phase naphthaleneDOI: 10000000000