Substituents

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The three Substituents properties specify the number of substituents that may be bonded to the selected atoms. In ChemDraw, a substituent is defined as a non-hydrogen atom connected by a bond of any order.

For example, in the figure below, the carbonyl carbon, indicated by the arrow in propanal, has a substituent count of two: the alpha carbon and the aldehyde oxygen. The double bond to the aldehyde oxygen counts as only one substituent and hydrogen atoms never count as substituents.

The substituent count atom property allows you to specify the number of bonds to an atom in the target structure. This includes bonds already drawn in the query structure.

The substituent options are described in the following table.

Option	Search Result
Unspecified	Default. Search is determined by the target database. Some databases (including ISIS) find compounds with any substitution at this atom and some databases (including DARC) find only compounds with substitution exactly as drawn.
Free Sites	Finds compounds in which the selected atoms may contain a range of substituents up to the number specified plus the number of bonds as drawn. A value of zero finds a substituent count as drawn. You can also use the Free Sites symbol in the Chemical Symbols palette to apply free sites. For more information, see , "Drawing Orbitals, Symbols, Arrows, Arcs, and Other Shapes" on page 75.
Up to	Finds compounds in which the selected atoms may contain a range of substituents up to the number specified.
Exactly	Finds compounds in which the selected atoms contain the exact number of substituents as specified, up to 15 substituents.