Ab initio (HF, post HF and DFT) conformational
and vibrational investigations of 2,4- dimethyl hexane
A. Aboulmouhajir1*, S. Mouatarif1, N. El Hamdani2, C. Van Alsenoy3
1Equipe de Recherche de Chemoinformatique et Spectroscopie et Chimie Quantique, Lab. de Chimie Physique ;
2Laboratoire de chimie bioorganique ; Dpt. de Chimie, Faculté des Sciences,
Université Chouaib Doukkali, B. P. 20, 24000 El Jadida, Maroc.
3Structural Chemistry Group, Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium;
* Corresponding author. E-mail: email@example.com
Received: 06 December 2012; revised version accepted: 28 March 2013
The 2,4- dimethyl hexane conformational isomerism have been investigated in detail based on HF, Post-HF and DFT calculations at different basis set. The effect of size of basis, ZPE, thermal contributions, electronic correlation and optimization methods on the conformational stability was discussed. The dependence of a structural parameters on a basis set and the methodology was also investigated. The rotational barriers from the most stable conformer to the lowest energy secondary conformers and their correspondent inversion barriers at both HF and MP2 methods using 6-31G* basis set have also been approached. A normal mode calculations of the most and less-stable conformers using a scaled ab initio force field in term of non redundant local symmetry coordinates have been made to elucidate the conformational dependence of the vibrational spectra.
Keywords: Ab initio; Conformational isomerism; Vibrational spectra; Scaled ab initio local symmetry force field.