Chemistry - Software for viewing a structure and altering bond angles

Solution 1:

Have a look at Avogadro!

• build your own structures or import files in various formats.
• optimize the geometry using different force fields
• change and measure bond length, bond angles and dihedral angles

Once you've used it, you don't want to miss it again.

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Geoff Hutchison, who cannot be praised enough for his child Avogadro, has given the right directions in his comment. I'm just adding some images to illustrate how easy angle adjustment is:

1. Draw a molecule in Avogadro
2. From the main menu, select Build -> Properties -> Angles or whatever the localized menu of your system shows (on my German machine, it is Ansicht -> Eigenschaften -> Winkeleigenschaften)
3. In the table that pops ups, select the angle you want to change. Note that the atoms of the selected angle are highlighted

4. Change the value for the angle. Note that the geometry of the molecule is immediately updated!

So again, I think that Avogadro is one of the best tools available and it is free and open source! Use it in education, use it in research and whenever you do, cite the Avogadro paper:
Hanwell, M. D.; Curtis, D. E.; Lonie, D. C.; Vandermeersch, T.; Zurek, E.; Hutchison, G. R.; Avogadro: an advanced semantic chemical editor, visualization, and analysis platform. J. Cheminf. 2012, 4 (1), No. 17. DOI: 10.1186/1758-2946-4-17.

Solution 2:

With the latest beta (5) of Chem4Word 2020 we have introduced the ability to set (fix) bond angles to any value in the range -180 to +180 (measured relative to Screen North)

1. Ensure that ACME (our brand new editor) is selected as your editor in the Options dialogue
2. Import your structure (MOLFile or CML)
3. EDit your structure, then right-click on the bond you wish to rotate.

If the bond is a terminal bond only that will be rotated about its anchor point Otherwise, the whole structure will be rotated.

The text box is free text and is validated to contain numbers in the range -180 to 180. If this contains invalid numbers a save can still be performed so that other changes can be carried out.

You can then export the structure as MOLFile (SDFile) or CML. Head over to Chem4Word Homepage to find out what else it can do.

Please read our beta testing guide Link on our download page before you start to use the beta.