Building a molecule and adjusting the dihedral angle.

Create the molecule.

• Add 3 carbon atoms in the Editor window.
  • Create bonds between atoms, with a double bond between the second (C2) and third carbon (C3).

• Add 1 oxygen atom with double bond to the first carbon (C1).

• Click on Comprehensive Cleanup (brush icon on left margin).
  • This the optimize the geometry and add the hydrogen atoms.

Adjust the dihedral angle.

• Click on Tools in the upper margin and select Adjust from the menu.
  • Click on the oxygen atom.

• Shift and click on the first carbon (C1).

• Shift and click on the second, then third carbon atoms.
  • Now the Adjust Dihedral Angle icon is available in the left margin.
    • Click on the icon (between arrow and brush).

• As an example, change the angle to 90.0.