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Substitution and protonation effects on spin–spin coupling constants in prototypical aromatic rings: C 6 H 6 , C 5 H 5 N and C 5 H 5 P
Author(s) -
Del Bene Janet E.,
Elguero José
Publication year - 2006
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1849
Subject(s) - chemistry , protonation , coupling constant , substitution (logic) , spin (aerodynamics) , coupling (piping) , aromaticity , crystallography , stereochemistry , computational chemistry , organic chemistry , molecule , thermodynamics , physics , quantum mechanics , ion , mechanical engineering , computer science , engineering , programming language
Ab initio equation‐of‐motion coupled cluster calculations have been carried out to evaluate one‐, two‐, and three‐bond 13 C 13 C, 15 N 13 C, 31 P 13 C coupling constants in benzene, pyridine, pyridinium, phosphinine, and phosphininium. The introduction of N or P heteroatoms into the aromatic ring not only changes the magnitudes of the corresponding XC coupling constants ( J , for X = C, N, or P) but also the signs and magnitudes of corresponding reduced coupling constants ( K ). Protonation of the heteroatoms also produces dramatic changes in coupling constants and, by removing the lone pair of electrons from the σ‐electron framework, leads to the same signs for corresponding reduced coupling constants for benzene, pyridinium, and phosphininium. CC coupling constants are rather insensitive to the presence of the heteroatoms and protonation. All terms that contribute to the total coupling constant (except for the diamagnetic spin‐orbit (DSO) term) must be computed if good agreement with experimental data is to be obtained. Copyright © 2006 John Wiley & Sons, Ltd.