Filter Substances by Structure Match

  • Updated
Download Icon Download

Structure matches for As Drawn, Substructure, and Similarity will be retrieved automatically. Select the type you wish to view.


As Drawn

As Drawn displays substances that match the structure exactly as drawn, as well as results that include:

  • Stereoisomers
  • Tautomers (including keto-enol)
  • Zwitterions
  • Charged compounds
  • Mixtures and salts in which the structure appears
  • Radicals or radical ions
  • Isotopes
  • Coordination compounds
  • Polymers in which the structure is a monomer

Back to Substances Page


In a Substructure match, the substances contain the structure query embedded within their chemical structure. Unless specified otherwise, the substructure must appear as drawn, and any substituent is allowed at any open atom position.


You can apply substructure query features to broaden or narrow your query. See Substructure Query Features.

Back to Substances Page


Filtering by similarity displays substance results that are similar to the queried structure.

Similarity scores are calculated based on the query structure. Substances with a higher similarity score are more similar to the search query.


You can filter the substance results by Similarity score ranges.


When viewing structure matches by similarity, each result's similarity score displays in the upper-right corner.


Analyze Structure Precision

For Structure Match with an As Drawn or Substructure filter, Analyze Structure Precision analyzes the structure's precision and categorizes/filters the substance results by Conventional Results and Tautomers/Zwitterions.


The Analyze Structure Precision link will be replaced by a Structure Precision filter with two potential bins:

  • Conventional Results: Conventional search results.
  • Tautomers and Zwitterions: Contains the smart search results, which in CAS SciFinder were the Loosely Associated Tautomers, Closely Associated Tautomers, and Other options. You may select the Conventional Results bin to exclude the smart search results or vice versa.