Brecher J. Graphical Representation Standards for Chemical Structure Diagrams. IUPAC Recommendations

Article. — Pure Appl. Chem. — 2008. — V. 80. — №2. — P. 277–410. — DOI: 10.1351/pac200880020277.The purpose of a chemical structure diagram is to convey information—typically the identity of a molecule—to another human reader or as input to a computer program. Any form of communication, however, requires that all participants understand each other. Recommendations are provided for the display of two-dimensional chemical structure diagrams in ways that avoid ambiguity and are likely to be understood correctly by all viewers. Examples are provided in many areas, ranging from issues of typography and color selection to the relative positioning of portions of a diagram and the rotational alignment of the diagram as a whole. Explanations describe which styles are preferred and which should be avoided.Bonds
Atom labels and other chemically significant text
Orientation of structures
Positioning of substituents
Charges, unpaired electrons, and lone pairs
Aromatic rings and other types of electron delocalization
Salts and related forms
Double bonds, dative bonds, and charge-separated forms
Variable attachment points and substituents
Tautomers
Annotations
Pseudobonds
Linear drawing style