From Molekel

ReferenceGuide: Edit bonds

Molekel supports the addition and removal of bonds. To add/remove bonds enable the molecule interaction mode then select atoms to link or bond to remove and click on the Add/remove bonds toolbar button.

A 720p video showing how to remove and add a bond is available here: http://molekel.cscs.ch/video/addremovebond.html

Add bond

1) Click on Interact with molecule toolbar button

2) Click on Pick atom/bond toolbar button

3) Click on first atom

4) Click on second atom while holding down the Shift key; this will enable the Add/remove bond button

5) Release the Shift key

6) Click on Add/remove bond toolbar button

Remove bond

1. Click on Interact with molecule toolbar button
2. Click on Pick atom/bond toolbar button
3. Click on bond to remove
4. Click on Add/remove bond toolbar button