Figure 6.

The geometry of the second transition state TS2 (φ = −160°, ψ = −176°, χ₁ = 176°). This transition state connects EN1 (Figure 5) and EN2 (Figure 7), and is for an OH rotation in the H₂PO₄⁻ ion of the enol-H₂PO₄⁻ complex. Selected interatomic distances are shown in Å. The imaginary frequency of this transition state is 131i cm⁻¹. Grey: carbon; white: hydrogen; blue: nitrogen; red: oxygen; orange: phosphorus.