Now that we’ve got the review stuff out of the way, let’s start talking about some molecules- specifically, alkanes, which are pretty much the simplest molecules we’ll deal with in this course. Alkanes are molecules composed of a carbon chain, meaning two or more carbons connected in a row. The name alkane implies that all of the carbons are connected by single bonds only. Easy enough, right? It gets a little more complicated when the carbons connect in a circular-like manner, which is known in organic chemistry as a “ring structure”. These are called cycloalkanes. Have two rings? Now we’ve got something known as a bicycloalkane. All of these have pretty important features that you’ll need to understand, because things only get more complicated from here.
By the end of this section, you should be a pro at naming these structures. Keep in mind there are slightly different rules when naming alkanes vs. cycloalkanes vs. bicycloalkanes, and another new set of rules when double and triple bonds come into play. But for now, we’ll be learning the general rules. Also, you’ll want to have a good understanding of strain energies in cycloalkanes as well as how isomerism factors in.
The last topic in this section that’s going to be a major factor is conformations. Ring structures have different ways they position themselves in 3D space. This is done in order to minimize energy caused by interactions between atoms, as well as strain energy. The most important ring is the cyclohexane, which is a ring composed of six carbon atoms and twelve hydrogens. This has two conformations: the chair conformation and the boat conformation. You’ll need to understand this, as well as the difference between an axial and an equatorial atom.
Tip
When initially learning about geometry and configuration, it is a lot easier to learn when visualizing an atom in 3D space. If you have access to a molecular model kit, this will really come in handy in the beginning. You may not need it later on when you become more comfortable with this material, but you can use it to learn how molecules orient themselves in space.
