Journal of Physical Chemistry A, Vol.113, No.24, 6795-6799, 2009
Ab Initio/DFT/GIAO-CCSD(T) Calculational Study of the t-Butyl Cation: Comparison of Experimental Data with Structures, Energetics, IR Vibrational Frequencies, and C-13 NMR Chemical Shifts Indicating Preferred C-s Conformation
The C-s conformation of the tert-butyl cation 3 was established to be the preferred global energy minimum using a combination of ab initio, DFT, and CCSD(T) methodology with correlation-consistent basis sets. The potential energy surface of methyl rotation involving the C-3v, C-s, and C-3h forms, however, in accord with previous studies, is quite flat. The computed IR absorptions of 3 indicate that it has the greatest degree of electron donation from C-H bonds into the C+-C bonds. The experimental C-13 NMR chemical shifts also agree very well with the experimental data.