Effect of Electronic Interactions on NMR 1 J CF and 2 J CF Couplings in cis - and trans -4- t -Butyl-2-fluorocyclohexanones and Their Alcohol Derivatives

Abstract

In order to study the influence of hyperconjugative, inductive, steric, and hydrogen-bond interactions on 1 JCF and 2 JCF NMR spin spin coupling constants (SSCCs), they were measured in cis- and trans-4-t-butyl-2-fluorocyclohexanones and their alcohol derivatives. The four isotropic terms of those SSCCs, Fermi contact (FC), spin dipolar (SD), paramagnetic spin orbit (PSO), and diamagnetic spin orbit (DSO), were calculated at the SOPPA(CCSD)/EPR-III level. Significant changes in FC and PSO terms along that series of compounds were rationalized in terms of their transmission mechanisms by employing a qualitative analysis of their expressions in terms of the polarization propagator formalism. The PSO term is found to be sensitive to proximate interactions like steric compression and hydrogen bonding; we describe how it could be used to gauge such interactions. The FC term of 2 JCF SSCC in cis4-t-butyl-2-fluorocyclohexanone is rationalized as transmitted in part by the superposition of the F and O electronic clouds.