When I took the DAT last year, KAPLAN's blue book did a horrible job for O-chem, simply because it doesn't discuss all the reactions that may show up on the test. What I saw in KAPLAN was a small fraction of all the O-chem reactions one should know for the DAT.
The G-chem section of KAPLAN does a fine job on discussing the topics, but you should complement that with doing lots of problems from destroyer.
Good Luck!