molecular entity quality double bond equivalent 2022-07-11T08:07:03Z DBE, degree/level of unsaturation, unsaturation index, index of hydrogen deficiency (IHD) The number of molecules of H2 that would have to be added to a molecule to convert all pi bonds to single bonds, and all rings to acyclic structures. http://www.chem.ucla.edu/~harding/IGOC/D/double_bond_equivalent.html