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Fig. 31 | Journal of Cheminformatics

Fig. 31

From: PubChem chemical structure standardization

Fig. 31

Functional group standardization II. Shown are cases that will not be modified (ac) and pre-processing steps carried out before the covalent single bond is replaced by a complex bond. Z indicates the transition metals and semiconductors (see Fig. 28). Z′ as used in b and c is a subset of the elements in Z. Terminal atoms are specified as such by visually restraining them using a parenthesis ‘]’. The transformation index for transition metal processing (df) is 15 (see the text for the description of transformation indices). a Bonds that are not modified (true for all elements in Z): double bond to oxygen, single bond to oxygen that is single-bonded to a metal M (see Fig. 28b), single bond to a halogen X, single bond to hydrogen. b Bonds that are not modified for elements in Z’: single bond to tetra-valent carbon. c Bonds that are not modified for elements in Z’: single bond to di-valent oxygen, single bond to di-valent sulfur, single-bond to tri-valent nitrogen. d A positive charge is moved from tetra-valent nitrogen to the transition metal. e Special case of carbon and nitrogen in carbon-only and nitrogen-containing five-membered aromatic rings, respectively. The same transformation applies to 7-membered aromatic carbon-only rings. f Special case of carbon and nitrogen double-bonded to oxygen

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