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Mills–Nixon effect in heteroanalogs of cyclopropabenzene
Author(s) -
EckertMaksić M.,
Maksić Z. B.,
Hodošček M.,
Poljanec K.
Publication year - 1992
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560420423
Subject(s) - heteroatom , proton , ring (chemistry) , spin (aerodynamics) , chemistry , bond , benzene , computational chemistry , proton spin crisis , physics , thermodynamics , quantum mechanics , organic chemistry , finance , economics
Structural properties of cyclopropabenzene and its heteroanalogs are studied at the SCF 6‐31 G level of theory. It is found that the Mills–Nixon ( MN ) type of localization within the benzene ring is present in these systems. The origin of the bond fixation lies in rehybridization at the carbon junction atoms. π‐electron bond orders usually follow changes within the sigma framework but can be misleading sometimes. It is shown that a judicious choice of heteroatoms can considerably enhance the MN effect. A refined and better definition of the MN effect is offered. Finally, present calculations and analysis of the results in terms of hybridization model and π‐bond orders strongly indicate that experimental 4 J (HCCMe) proton–proton spin–spin couplings over four bonds can be used in identification of the MN effect only with extreme caution.