Fig. 20

Differences between PubChem-standardized and InChI-derived structures—valence models. Examples illustrate modifications from InChI-derived structures applied in Verify Hydrogen (a) and Standardize Explicit Hydrogen (b) during PubChem standardization. a SID 1300. State in (i) as deposited. InChI-derived structure results in alternate Kekulé structure (ii). Subsequent PubChem standardization adds positive charge to tetra-valent nitrogen in step Verify Hydrogen (iii). The final result of PubChem standardization is shown in (iv). b SID 576083. State in (i) as deposited. Standard InChI-derived structure disconnects nitrogen and palladium as well as palladium and oxygen and places charges as appropriate (ii). During subsequent PubChem standardization, two hydrogen atoms are added to each oxygen atom (iii). The result of original PubChem standardization is shown in (iv). Even though (iii) does not possess the complex bonds between nitrogen, palladium and oxygen, the SMILES strings generated for the structures in (iii) and (iv) are identical