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Analysis of the nitrile and methyl torsional vibrations of n ‐propyl cyanide in its S 0 electronic state
Author(s) -
Castro M. E.,
MuñozCaro C.,
Niño A.
Publication year - 2010
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.22810
Subject(s) - nitrile , cyanide , vibration , computational chemistry , chemistry , state (computer science) , physics , organic chemistry , quantum mechanics , mathematics , algorithm
Abstract This work presents a structural and vibrational theoretical study of n ‐propyl cyanide as a function of the nitrile and methyl torsional modes. A potential energy hypersurface is built at the MP4(SDQ)/aug‐cc‐pVTZ//MP2/aug‐cc‐pVTZ theory level. The equilibrium structure is found in a gauche conformation. Another minimum is found for the trans form. The maximum appears in a cis conformation. For the first time, the interconversion barriers between the different forms are calculated. A two‐dimensional anharmonic vibrational Hamiltonian is built for the nitrile and methyl torsional modes. We find the vibrational energy levels to organize in two stacks associated to the gauche and trans forms. Fundamental frequencies of 113.12 and 220.54 cm −1 are predicted for the nitrile and methyl torsions in the equilibrium, gauch e, conformer. In addition, we find symmetry allowed transitions between the gauch e and trans energy levels stacks. The lowest transition is predicted to appear at 24.49 cm −1 . © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011