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

In order to study the influence of hyperconjugative, inductive, steric, and hydrogen-bond interactions on 1 J CF and 2 J CF 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 J CF SSCC in cis-4-t-butyl-2-fluorocyclohexanone is rationalized as transmitted in part by the superposition of the F and O electronic clouds.