CHEMISTRY COMMUNITY

Does is matter if you place the substituents below or above the parent chain? Especially if there are two substituents for the same carbon, how do you determine which one goes above or below?

The orientation of substituents does not matter for most molecules because the bonds can rotate, so any number of different orientations can be correct as long as they yield the same name. The only significant exception is in the case of geometric isomers. When choosing orientations around a double bond, one must consider whether it is cis(Z) or trans(E).

If you have a chain of sp³ carbons, then writing above or below the chain does not matter. Be careful with geometric isomers, like cis and trans, since orientation does matter for those molecules.