Ring Tool
The Ring tool places complete rings in one click. Press R to activate it, pick a template from the toolbar flyout, then click empty canvas, an existing atom, or an existing bond. Each target gives a different placement mode: free placement, attachment, or fusion.
Ring templates
Long-press or click the Ring toolbar button’s flyout to choose a template. Two groups are available:
- Carbon rings: cyclopropane (3), cyclobutane (4), cyclopentane (5), cyclohexane (6), cycloheptane (7), cyclooctane (8)
- Aromatic heterocycles: benzene, pyridine, pyrrole, furan, thiophene
Heterocycle templates place the heteroatom (N, O, or S) at one vertex automatically. For five-membered aromatic heterocycles, the alternating double bonds are offset so none lands on the heteroatom.
Default behavior
With no template selected, the tool defaults to a six-membered ring placed as benzene: alternating double bonds in Kekulé style plus an aromatic circle record. Hold Shift while clicking to place the non-aromatic version (plain cyclohexane) instead.
Aromatic rings render with alternating double bonds by default. To show a circle instead, use Structure, then Display, then Aromatic Display. You can also override the display per bond in the Object Properties panel.
Placing on empty canvas
Click empty space and release to drop the ring with its default orientation. To rotate it first, click, hold, and drag: the drag direction points one vertex toward the cursor. The rotation snaps to 30 degree increments when Smart Guides are on; hold Shift or Alt during the drag for free rotation. Release to commit.
Attaching to an existing atom
Click an existing atom to attach the ring at that vertex (a spiro-style attachment when the atom already sits in another ring). With a plain click, the ring points away from the atom’s existing bonds. Drag before releasing to swing the ring around the anchor atom in 30 degree steps; hold Shift for free rotation.
While dragging, if one of the new ring’s edges lines up with an existing bond of standard length (within about 15 degrees), the preview snaps to that bond and releasing fuses the ring onto it instead of attaching at a single atom. Hold Shift to suppress this snap.
Fusing onto a bond
Click the middle of an existing bond (away from both endpoints) to fuse the ring onto that bond. The two bond atoms become shared ring vertices and no duplicate bond is created. By default the new ring goes on the side opposite any existing ring; drag across the bond before releasing to flip which side it lands on.
When fusing an aromatic template, bond orders alternate around the new ring and account for double bonds the shared atoms already carry, so no atom ends up with two double bonds.