While I haven't taken the MCAT, I have finished Organic Chemistry. For us, the second half of Ochem was learning mechanisms and reactions with some emphasis on sugars and polymers. I don't know that you'll necessarily learn much from the second part of OChem that is pertinent to the MCAT but I will definitely say that without it, your skills will be pretty far behind because of all the practice that you are missing out on. The concepts might have been rehashed a bit in Organic 2 but without them, I don't know that I would have understood most of it as well. To give this some credibility, I scored in the top 13% in the nation in OChem as I'm sure many of the premeds who took the ACS exam did so I promise I'm not just blowing smoke.