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Stabilization of carbocations CH3+, C2H5+, i-C3H7+, tert-Bu+, and cyclo-pentyl+ in solid phases : Experimental data versus calculations. / Stoyanov, Evgenii S.; Nizovtsev, Anton S.
в: Physical Chemistry Chemical Physics, Том 19, № 10, 08.03.2017, стр. 7270-7279.Результаты исследований: Научные публикации в периодических изданиях › статья › Рецензирование
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TY - JOUR
T1 - Stabilization of carbocations CH3+, C2H5+, i-C3H7+, tert-Bu+, and cyclo-pentyl+ in solid phases
T2 - Experimental data versus calculations
AU - Stoyanov, Evgenii S.
AU - Nizovtsev, Anton S.
N1 - Publisher Copyright: © the Owner Societies 2017.
PY - 2017/3/8
Y1 - 2017/3/8
N2 - 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 CHClubsuit sign) from each CH3/CH2 group transfers its σ-electron density to the empty 2pz orbital of the sp2 C atom, whereas the σ-electron density on the other CH bonds of the CH3/CH2 group slightly increases. From experimental IR spectra it follows that donation of the σ-electrons from the CHClubsuit sign bond to the 2pz C-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/CH2 group. As a result, all CH stretches of the group are red shifted, and IR spectra show typical CH3/CH2 group 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.
AB - 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 CHClubsuit sign) from each CH3/CH2 group transfers its σ-electron density to the empty 2pz orbital of the sp2 C atom, whereas the σ-electron density on the other CH bonds of the CH3/CH2 group slightly increases. From experimental IR spectra it follows that donation of the σ-electrons from the CHClubsuit sign bond to the 2pz C-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/CH2 group. As a result, all CH stretches of the group are red shifted, and IR spectra show typical CH3/CH2 group 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.
KW - STABLE CARBONIUM-IONS
KW - BUTYL CATION
KW - CONDENSED PHASES
KW - HYPERCONJUGATION
KW - PROTONATION
KW - ENERGETICS
KW - CHEMISTRY
UR - http://www.scopus.com/inward/record.url?scp=85015784916&partnerID=8YFLogxK
U2 - 10.1039/c6cp06839a
DO - 10.1039/c6cp06839a
M3 - Article
C2 - 28239699
AN - SCOPUS:85015784916
VL - 19
SP - 7270
EP - 7279
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
SN - 1463-9076
IS - 10
ER -
ID: 9053498