Cyclopentyl, cyclohexyl, and cycloheptyl cations: computational studies of the structures, stability, 13C NMR chemical shifts, and possible rearrangement pathways

Abstract

Various structures of the cyclopentyl cation were computed at the MP2/cc-pVTZ and CCSD (T)/cc-pVTZ levels. Energetically, the classical cyclopentyl cation 1 and the 1,2-hydrogen-bridged structure 3 were found to be almost identical. The structures and energies of the cyclohexyl and cycloheptyl cations were also calculated at the MP2/cc-pVTZ level. The σ-delocalized nonclassical ion 16 was found to be the lowest energy structure for the cycloheptyl cation. The 13C NMR chemical shifts of the ions were also computed and compared with the experimental results.