𝐴 𝐵 = exp 𝐸(𝐴)-𝐸(𝐵) 𝑘𝑇 Interestingly, the calculated molecular dipole of the organomercuric chlorides was approximately 3.5 Debye, whereas that of the organomercuric triflates was about 7.5 Debye. This speaks to a greater ionic character for the organomercuric triflate species, which no doubt contributes to its reactivity, and may be the underlying reason for the observed selectivity. We analyzed the molecular orbitals to better quantify this polar effect. In the extensively delocalized HOMO of each organomercurial triflate, hyperconjugation of one or both silanol oxygen lone pairs into the σ* of the C-Hg bond is observed (Figure ). The HOMO of the 5-exo rearranged product 73-OTf is lower in energy than that of the 6-endo intermediate 72-OTf by 1.47 kcal/mol. It follows that the presence of an additional silanol oxygen lone pair has a destabilizing effect on the HOMO for the 6-endo intermediate, which may be the ultimate driving force for the observed 5-exo selectivity.