The structural dependence of 13C, 13C coupling constants in cyclopropanes

The smallest one-bond carbon—carbon coupling constants of cyclopropane derivatives have been measured for 1-¹³C]cyclopropane-1,1-dicarboxylic acid and cyclopropanecarboxylic acid. The ¹³C, ¹³C coupling constants of cyclopropylcarbinol have also been determined. The dependence of ¹J(CC) of the three-membered ring on different substituents and hybridization effects is evaluated. The carbon—carbon coupling constant of the unsubstituted cyclopropane is discussed on the basis of self-consistent perturbation theory (SCPT) and s character calculations (localized bond orbitals), and the results are compared with the experimental finding. It is shown that the ¹J (CC) can be interpreted by assuming a dual-pathway coupling mechanism.