In the case of overlapping graphics, you may bring one to the foreground using the Send to Back tool.
Do one of the following to assign a selected structure to the back layer of overlapping graphics:
Select the structure and click on the Send to Back tool in the Chemistry toolbar.
Select the structure and choose Arrange > Send to Back.
Select the structure, right-click anywhere in the drawing area to bring up the Drawing Area pop-up menu, and choose Arrange > Send to Back from the menu.
See also: