This topic identifies techniques for controlling ring formation in substructure search results.

Substructure searching retrieves matches where rings or chains of a structural skeleton are embedded within a larger ring system.

By default, a substructure search on retrieves the following:

Structure matches	Example
Exactly as you drew it
Substituted at open positions
With the ring side-fused to another ring
With the ring spiro-connected to another ring

By default, a substructure search on retrieves the following:

Structure matches	Example
Exactly as you drew it (with assumed hydrogens)
Substituted at open positions
With the chain bonds forming rings
With the chain atoms part of a spiro ring

The Lock Rings tool   controls ring formation.

The Lock Rings tool does not prevent substitution at open positions.

Tools and structure drawing techniques are available to control substitution.