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Tips for Molecular Formula Searching

If the molecular formula
you are searching
Then your action is to
Represents a multi-component
substance
Search the dot-disconnected formula in the /MF
index. Arrange the components as follows:
  • All components contain carbon -
    Arrange by descending carbon count
  • No carbon-containing components -
    Arrange alphabetically by first
    element in each component
  • Both carbon and non-carbon
    components-
    Carbon components come first
Represents the salt of an acid Search the dot-disconnected formula
in the /MF index

Replace the metal with hydrogen in the acid
formula and dot-disconnect the metal

Represents the salt of an amine Search the dot-disconnected formula
in the /MF index

Remove one hydrogen from amine
formula and add it to the anion.
Dot-disconnect the resulting formula

Retrieves too many hits Refine the answer set by:
  • Requiring that rings be present
    (AND RSD/FA)
  • Eliminating ring-containing
    substances (NOT RSD/FA)
  • Adding chemical name segments
Reproduced with the permission of CAS, a Division of the American Chemical Society, from "Tips for Searching the CAplus & REGISTRY Files." (CAS9613-0298)