Indirect ¹³C¹³C couplings in benzene and the contribution of their anisotropies to the direct couplings in the oriented molecule

Abstract

Abstract The indirect ortho and para carbon‐carbon coupling constants in benzene were determined utilizing the deuterium isotope effect on the carbon chemical shifts in 1‐ d 1 ‐ and 1,3,5‐ d 3 ‐benzene. The measurements gave for J (CC, ortho ) and J (CC, para ) the values of 55.3 ± 0.5 Hz and 10.08 ± 0.10 Hz, respectively. The ratios of the direct dipolar CC coupling constants were calculated using the previous results of 1‐ 13 C‐benzene in an oriented phase. These ratios differ from the theoretical ones obtained assuming the benzene ring to be hexagonal, showing significant indirect contributions in the D values.