A final pathway that could potentially be envisioned is direct oxocarbenium capture by uracil, followed by deprotonation. In essence, this corresponds to the S N 1 pathway, but without the initial ribose-phosphate dissociation. As our calculations indicate that the rate-determining step of the S N 1 pathway is retained in this final alternative, both are equally unlikely to transpire: the energetic spans, as well as the susceptibility to electric field effects, are the same.