TY - JOUR
T1 - π-σ* hyperconjugation mechanism on methyl rotation in cationic state of substituted toluenes
AU - Kawai, Masaaki
AU - Nakai, Hiromi
N1 - Funding Information:
Part of the calculations was performed at the Research Center for Computer Science (RCCS) of Okazaki National Research Institutes and the Media Network Center (MNC) of Waseda University. Part of this study was supported by a grant-in-aid for Scientific Research on Priority Areas `Molecular Physical Chemistry' from the Japanese Ministry of Education, Culture, Sports, Science and Technology, and by a Waseda University Grant for Special Research Projects.
PY - 2001/11/15
Y1 - 2001/11/15
N2 - Internal rotation of methyl group in cationic state of substituted toluenes has been investigated by the ab initio theory. Substituted groups studied here are F (fluorotoluene), NH2 (toluidine), OH (cresol), and CN (tolunitrile). The rotational barriers in the neutral and cationic ground states calculated by the Hartree-Fock method are in reasonable agreement with experimental values. Variations of the rotational barriers by the ionization are shown to be directly correlated with the stability of the HOMO. In the HOMO and HOMO-1, a new type of orbital interaction named π-σ hyperconjugation (HC) appears and determines their stability. The π-σ HC mechanism clarifies the differences between ortho- and meta-systems, between π-electron donating and accepting substituents in the cationic state.
AB - Internal rotation of methyl group in cationic state of substituted toluenes has been investigated by the ab initio theory. Substituted groups studied here are F (fluorotoluene), NH2 (toluidine), OH (cresol), and CN (tolunitrile). The rotational barriers in the neutral and cationic ground states calculated by the Hartree-Fock method are in reasonable agreement with experimental values. Variations of the rotational barriers by the ionization are shown to be directly correlated with the stability of the HOMO. In the HOMO and HOMO-1, a new type of orbital interaction named π-σ hyperconjugation (HC) appears and determines their stability. The π-σ HC mechanism clarifies the differences between ortho- and meta-systems, between π-electron donating and accepting substituents in the cationic state.
UR - http://www.scopus.com/inward/record.url?scp=0035528988&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0035528988&partnerID=8YFLogxK
U2 - 10.1016/S0301-0104(01)00482-7
DO - 10.1016/S0301-0104(01)00482-7
M3 - Article
AN - SCOPUS:0035528988
SN - 0301-0104
VL - 273
SP - 191
EP - 196
JO - Chemical Physics
JF - Chemical Physics
IS - 2-3
ER -