Searching by Functional Groups and Common Heterocyclic Rings
Chemical Abstracts Service, 1993. Reproduced for educational purposes with permission from CAS, a Division of the American Chemical Society.
- CAS has defined approximately:
- 160 terms which represent structural features
- 40 short linear descriptions for common heterocycles
- 10 functional group class terms
- Functional Group and Ring terms are quick and easy to search, allow you to do general reaction searching, and can be used to overcome structure search system limits.
- While Functional Groups and Ring terms may be used to search reactants, reagents, and products, they may not be used to search solvents and catalysts.
Role Qualifiers for Functional Groups
- Group is present in the reaction, not that the group definitely
participates in the reaction(s):
Group is in a reactant /FG.RCT Group is in a reagent /FG.RGT Group is in a product /FG.PRO Group has any role /FG
- If Group is involved in the reaction, then use these indexes:
Group on reactant takes part in the reaction /FG.RXN Group is formed in the reaction /FG.FORM Group is present, but does not participate in the reaction /FG.NON
=> s nitrile/fg.pro [to find a nitrile in the product]
=> s nitrile/fg.form [to find nitrile formed in the reaction]
Using Multiple Functional Group Search Terms
- The (S) Operator
- The (S) proximity operator specifies that the reacting functional group is actually converted to the forming functional group. The definition of conversion is that at least one atom in the reacting group is still present in the forming group.
- For example, to retrieve only reactions in which a nitrogen atom in the
reacting functional group is converted to a primary amine:
=> s azide/fg.rxn (s) primary amine/fg.form
- The (S) operator cannot be used with the /FG.RGT, FT.NON, or /FG indexes
- Use (S) proximity for the best precision.
- The (L) Operator
- The (L) proximity operator specifies that the functional groups be in the same reaction. This is a broader specification than the (S) operator.
- The (L) operator may be used with the /FG.RGT, FT.NON, or /FG indexes.
“In the Presence of” Reactions
- To look for reactions in the presence of a functional group, we combine reacting, forming, and non-reacting functional groups using (S) and (L) proximity.
- For example, to look for the conversion of an azide to a primary amine in the
presence of a primary alcohol.
=> s azide/fg.rxn (s) primary amine/fg.form (l) primary alcohol/fg.non