Yes I agree with previous posts, don`t memorize, you must understand it. You know that the questions will be different on each DAT, I wouldn`t gammble with selective memorization. You never know what they decide to put on the DAT. Your safest bet is to learn everything from the organic chemistry college course. By learn I mean understand how to do the problems. You shouldn`t memorize any overly complex structures and their molecular weights, but know how to name organic compounds.