Substitution and protonation effects on spin–spin coupling constants in prototypical aromatic rings: C6H6, C5H5N and C5H5P

✍ Scribed by Janet E. Del Bene; José Elguero

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 137 KB
• Volume: 44
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1849

✦ Synopsis

Abstract

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 XC 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. CC 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.