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Transmission mechanisms of inter‐proton long‐range couplings in substituted anisoles
Author(s) -
de Kowalewski D. G.,
Contreras R. H.,
Engelmann A. R.,
Facelli J. C.,
Durán J. C.
Publication year - 1981
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270170314
Subject(s) - proton , coupling constant , sign (mathematics) , chemistry , range (aeronautics) , coupling (piping) , transmission (telecommunications) , ring (chemistry) , space (punctuation) , methyl group , molecular physics , electron , group (periodic table) , computational chemistry , atomic physics , crystallography , physics , stereochemistry , materials science , quantum mechanics , organic chemistry , mathematics , mathematical analysis , linguistics , philosophy , electrical engineering , metallurgy , composite material , engineering
Inter‐proton long‐range and ring couplings were measured in o ‐anisaldehyde and in seven disubstituted anisoles. In order to investigate the transmission mechanisms of long‐range couplings with the methoxy group, partially restricted molecular orbital (PRMO) calculations were carried out within the FPT‐INDO method on o ‐anisaldehyde. σ‐ and π‐electron, and through‐space transmitted components were separated. For the energetically favoured trans ‐OMe conformation a through‐space component was found for the couplings of the methyl protons with the ortho ‐proton, and it was found that its sign, as well as its magnitude, depends on their relative positions. If free rotation, however, is assumed for the methyl group, the averaged value for this coupling constant is negative.