C13–H and X—H Coupling Constants for Compounds of the Type X(CH3)4

Abstract

From high‐resolution proton magnetic resonance experiments, absolute magnitudes of J_C¹³–H and J_X–C–H have been determined for compounds of the type X(CH₃)₄, where X=Si, Ge, Sn, and Pb. The J_C¹³–H values yield the s characters of the carbon orbitals in the C–H and C—X bonds as well as the Juan—Gutowsky s character affinity Δ_X. Rough calculations of J_X–C–H based on the Fermi contact term give widely varying results depending on the value of the effective charge used. A straight line correlation of J_X–C–H with n³ can be explained crudely on the basis of the Fermi contact term.