Similarly, in the case of 5CF3,C2F5, the computed reverse rate constant results in a kT of 3 × 10 -6 s -1 with a tunneling t1/2 of 20 hrs versus kT of 0.3 s -1 and t1/2 of ~2 s calculated for the forward reaction at 298.15 K, indicating the ephemeral character of P(V) oxide tautomer and thereby, this might explain the reason why only the P(III) form is present in the reported NMR spectra.