Table 2 Tautomerism patterns detected by InChI

M = Q − ZH ↔ MH − Q = Z or M = Q − Z⁻ ↔ M⁻ −Q = Z

M, Z = N^III, O^II, S^II, Se^II, Te^II (Roman superscripts designate chemical valence)

Q = C, N, S, P, Sb, As, Se, Te, Br, Cl, I

H = hydrogen, deuterium, or tritium

The “=” bond may be a double bond, a bond in the alternating single/double bond ring, or a “tautomeric” bond (shown in blue)

The H atom below can be replaced with a negative charge