Tables for
Volume F
Crystallography of biological macromolecules
Edited by M. G. Rossmann and E. Arnold

International Tables for Crystallography (2006). Vol. F. ch. 24.3, p. 664

Section 2D chemical connectivity data

F. H. Allena* and V. J. Hoya

aCambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, England
Correspondence e-mail: 2D chemical connectivity data

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The formal two-dimensional chemical structural diagram for each entry (Fig.[link] is encoded in the form of a compact connection table. Chemical connectivity is recorded in terms of a set of atom and bond properties. The atom properties recorded are: atom number, element type, number of connected non-H atoms, number of terminal H atoms and the formal atomic charge. Bond properties are encoded as a pair of atom numbers and the formal chemical bond type that connects those atoms. Bond types employed in the CSD connectivity descriptions are: single, double, triple, quadruple (metal–metal), aromatic, delocalized double and π bonds. Bond types are (automatically) coded negative if the bond forms part of a cyclic system.


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2D chemical connectivity data for a simple organic molecule.

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