As benzoyl radical is very big, E isomer is preferable because of sterical difficulties. E-isomer is less polar, because 2 -C=O groups will be located in the opposite direction relatively to each other. in Z they will be on the same side. Solution As benzoyl radical is very big, E isomer is preferable because of sterical difficulties. E-isomer is less polar, because 2 -C=O groups will be located in the opposite direction relatively to each other. in Z they will be on the same side..