title: Stabilization of carbocations CH3+, C2H5+, i-C3H7+, tert-Bu+, and cyclo-pentyl+in solid phases: experimental data versus calculations.
abstract: Comparison of experimental infrared (IR) spectra of the simplest carbocations (with the weakest carborane counterions in terms of basicity, CHB11Hal11-, Hal = F, Cl) with their calculated IR spectra revealed that they are completely inconsistent, as previously reported for the t-Bu+cation [Stoyanov E. S., et al. J. Phys. Chem. A, 2015, 119, 8619]. This means that the generally accepted explanation of hyperconjugative stabilization of the carbocations should be revised. According to the theory, one CH bond (denoted as ) from each CH3/CH2group transfers its σ-electron density to the empty 2pzorbital of the sp2C atom, whereas the σ-electron density on the other CH bonds of the CH3/CH2group slightly increases. From experimental IR spectra it follows that donation of the σ-electrons from the bond to the 2pzC-orbital is accompanied by equal withdrawal of the electron density from other CH bonds, that is, the electrons are supplied from each CH bond of the CH3/CH2group. As a result, all CH stretches of the group are red shifted, and IR spectra show typical CH3/CH2group vibrations. Experimental findings provided another clue to the electron distribution in the hydrocarbon cations and showed that the standard computational techniques do not allow researchers to explain a number of recently established features of the molecular state of hydrocarbon cations.
authors.affiliation: Vorozhtsov Institute of Organic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia. evgenii@nioch.nsc.ru and Department of Natural Sciences, National Research University, Novosibirsk State University, Novosibirsk 630090, Russia.
authors.forename: Evgenii S
authors.identifier: http://orcid.org/0000-0001-6596-9590
authors.initials: ES
authors.lastname: Stoyanov
authors.affiliation: Department of Natural Sciences, National Research University, Novosibirsk State University, Novosibirsk 630090, Russia and Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia.
authors.forename: Anton S
authors.identifier: http://orcid.org/0000-0002-5383-2711
authors.initials: AS
authors.lastname: Nizovtsev