This can be traced back to a less stabilizing dispersion interaction (ΔΔEint(disp) = -7 kJmol -1 ) and a slightly more destabilizing electronic interaction in 6-4 (ΔΔEint(elec) = 4 kJ mol -1 ). While the dispersion interaction correlates with the bending of the molecule (Figure ), the difference between the electronic interactions of the transition state originates from the slightly smaller C-C bond distance of 6-4 and 8-4 (Δd(C-C) = 0.02 Å). This minor change results in a minimal increase in electrostatic interaction (ΔΔEelstat = -9 kJ mol -1 ) but also a larger increase in Pauli repulsion (ΔΔEPauli = 15 kJ mol -1 ), which cannot be compensated by the orbital interaction (ΔΔEorb = -2 kJ mol -1 ). A detailed discussion of the NOCV analysis can be found in the SI.