One of the toughest parts of organic chemistry is understanding the mechanisms behind reactions. Immediately, many pre-dental students want to know if they have to go through the same torture as they did in their college organic chemistry classes to memorize these complex reactions.
You don’t have to know the mechanisms for many of the reactions. However, you are expected to know and understand the mechanisms in basic halogenations, SN1, SN2, E1, and E2 reactions. These are topics that can definitely show up on your exam, such as what the intermediate in a reaction is. As far as knowing how ozonolysis, Diels-Alder, Wittig, and other name reactions work, you do not need to know their mechanisms. You’ll often just be asked what are the reactants or products in these more complex reactions.
That said, I still think it is very beneficial to understand mechanisms. Mechanisms are not voodoo, they don’t occur without a reason. Understanding those reasons and why things proceed as they do will inevitably help you deeply understand organic chemistry and ace the DAT.