I doubt schools will compare your score on the o-chem section from the DAT with your o-chem grade. What will help to straighten out the poor performance in o-chem is a good overall science GPA. They will also look at the TS score from the DAT, and see a solid 21. Assuming you did well in other science classes, I don't think you need to worry about it.
Personally, I got a C in O-chem 1, retook it and got a B+, got a B in O-chem 2, got a 19 in O-chem in 2005, took 4 years off, retook the DAT, got a 19 again, and got 1 acceptance.