Carbon‐13, ¹H coupling constants for benzene and the tropylium ion

The 13 C, 1 H spin–spin coupling constants for benzene and tropylium fluoroborate have been measured from the 13 C NMR spectra of [D 5 ]benzene and the [D 6 ]tropylium ion using a new experimental technique which employs highly deuterated compounds and 2 D‐decoupling. For benzene the new data are in good agreement with earlier results. For the tropylium ion we find 1 J = 166.79, 2 J ≃ 0, 3 J = 9.99 and 4 J = (−)0.64 Hz. Secondary isotope effects for 13 C chemical shifts, including one over four bonds, are reported.