The complexity of organic chemistry lies in the memorization and understanding of its general formulas. Hydrocarbons only contain carbon and hydrogen, and their structures can be chain-like or cyclic. Double bonds indicate alkenes, triple bonds indicate alkynes, while those connected by single bonds are alkanes. Aliphatic compounds form chain-like structures, while aromatic compounds have benzene rings. It should be noted that isomers have the same molecular formula but different structures, so their general formulas are interchangeable. In organic chemical reactions, the formation of derivatives depends on the changes of functional groups. For example, carboxylic acids contain carboxyl and hydrocarbon groups, while ketones, ethers, and amines contain carbonyl, ether bonds, and amino groups, respectively. In addition, phenol is a substance with a hydroxyl group on a benzene ring, while naphthalene is a compound with two benzene rings connected. In organic chemical reactions, oxidation and reduction reactions are common types, where the oxidation of alcohols produces ketones or aldehydes. Meanwhile, halogenation is also one of the important reactions in organic chemistry. Finally, polymerization is the process of connecting monomers into linkages, and breaking π bonds is the key step to connect these linkages in series.