From here on out we will continue our study of sp2 hybridized carbon atoms but now instead of studying carbon-carbon pi bonds, we are going to shift our focus to carbonyls.
A carbonyl group is just a carbon double bonded to an oxygen(C=O). Carbonyl chemistry is rich with long lists of reactions which are often daunting to students. If you look for patterns though, the amount of new material to learn is manageable. Once again, you will be looking at substitution, elimination, and addition reactions, except this time on a sp2 hybridized carbon atom with a double bond to oxygen. Before you dive into carbonyl chemistry, it is really important to have a solid understanding of the resonance structures of a carbonyl.
Review why carbonyls are electrophilic, how to make a carbonyl more electrophilic, and how they can help stabilize a negative charge on a neighboring carbon atom by watching the videos below. Then practice the fundamental arrow pushing patterns in the recommended puzzles.