STN Express logo

Ring Tool

The Ring Tool can be used to draw various ring systems:

To draw isolated rings:

  1. Type the ring size that you want in the Ring Description box, os use the scroll bar to display ring sizes available.

  2. Place the ring cursor where you want the ring and click.  The ring is drawn vertically upwards from the cross in the center of the cursor, using the current atom type but not the current bond type.  Resent the current atom to C before using the Ring Tool.  Additional rings of the same type will be drawn on subsequent clicks. The saturated and unsaturated rings displayed in the Ring Tool dialog can be selected directly by pointing to them and clicking.

To draw fused rings:

Rings can be fused, with an appropriate ring size selected, by pointing to an existing ring atom for spiro fusion, or to the middle of an existing ring bond for fusion along that bond.

Note: The cross in the center of the cursor is the "active point" for ring fusion, and the cursor changes when positioned over an atom or bond (displaying an "A" or "--"). Fused ring systems, consisting of 6, 5, or 4 membered rings, can also be typed into the Ring Description box in the Ring Tool dialog. The direction of fusion is left to right, the direction can be changed from horizontal using "U" or "D" for up or down. For example, 66U6D5 draws a steroid skeleton.


Click right on the Ring Tool to select the default ring system. Also, click right in the drawing area to place alternating single and double bonds for the default ring system.

Copyright © 2017 American Chemical Society. All Rights Reserved.