Athanor by arbastro
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How to show R and S, E and Z labels

Turn on View › Show stereochemistry. Each stereocenter gets R or S and each stereo double bond E or Z, worked out from the CIP priority rules and updated as you draw.

Steps

  1. Draw or insert the structure, for example menthol (press / and type menthol).
  2. Choose View › Show stereochemistry in the Main menu.
  3. Every stereocenter shows (R) or (S), and every double bond with a defined geometry shows (E) or (Z).

Menthol with R and S labels on its three stereocenters.Menthol with R and S labels on its three stereocenters.

The labels follow the CIP rules (Cahn, Ingold and Prelog), which rank the groups on each center. Change a wedge to a hash and the label flips at once. See How to draw wedge and hash bonds.

For one structure only

Select the structure. In the Properties panel, under Display, set R/S labels to On.

Note

A stereocenter drawn without a wedge or hash has no label, and the issues badge counts a warning such as "C's configuration is not drawn".

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 add charges, radicals and lone pairsPress Q for the Charges tool, pick plus (+), minus (-), lone pair (L), radical, diradical, delta plus or delta minus, and click the atom. clear takes every mark off an atom.

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Last updated Nov 12, 2026