If Coenzyme Q is reduced by one equivalent, the following structure results, a ubisemiquinone, and is denoted QH. Note the free radical on one of the ring oxygens (either oxygen may become a free radical, in this case the top oxygen is shown as such).

Click this LINK to visit the original image and attribution information. Right click on the image to save the 800px teaching JPEG.



If Coenzyme Q is reduced by one equivalent, the following structure results, a ubisemiquinone, and is denoted QH. Note the free radical on one of the ring oxygens (either oxygen may become a free radical, in this case the top oxygen is shown as such).