Athanor by arbastro
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How to choose undefined stereocenters

Select the structure and choose Object › Chemistry › Choose undefined stereocenters. Athanor proposes wedges; Accept keeps them, Reject proposes hashes, and rejecting again leaves them undefined.

Steps

  1. Select a structure with a stereocenter that has no wedge or hash, for example butan-2-ol drawn flat.

  2. Choose Main menu › Object › Chemistry › Choose undefined stereocenters.

  3. Athanor proposes wedges and shows them on the drawing.

    Suggested: Wedges for 1 stereocenter, with Accept and Reject.Suggested: Wedges for 1 stereocenter, with Accept and Reject.

  4. Press Accept to keep them, or Reject to see the other configuration, hashes.

    Suggested: Hashes for 1 stereocenter. Reject to leave them undefined.Suggested: Hashes for 1 stereocenter. Reject to leave them undefined.

  5. Press Accept for the hashes, or Reject again to leave the stereocenters undefined.

The issues badge warns about a stereocenter with no wedge or hash; this command is the quickest way to settle each one. See Why an atom is flagged.

Drawing basicsHow to draw wedge and hash bondsWith the Bond tool, press U for wedge, H for hash or Y for wavy, then click a bond to change it or click empty canvas to draw a new one. The narrow end sits on the stereocenter. View › Show stereochemistry labels each center R or S.Atoms, bonds and ringsHow to list every stereoisomer of a structureSelect the structure and choose Object › Chemistry › Stereoisomers. Every stereoisomer is listed with its own R/S and E/Z, meso forms counted once; press Place on one or Place all.Troubleshooting and FAQWhy an atom is flaggedThe badge at the bottom left of the canvas counts problems in what you drew, such as a carbon with five bonds (an error) or a stereocenter with no wedge (a warning). Click it to see the list. Athanor flags problems and never changes your structure on its own.

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Last updated Nov 12, 2026