Alright, by now you should have a pretty good understanding of what molecules look like when they have a carbon chain, how they orient themselves, how to name them, etc. Let’s mix it up a little by making things a tiny bit more complicated—let’s add double bonds to the mix. A molecule with a carbon chain containing one or more double bonds is known as an alkene. That means a ring structure with a double bond is ( … you guessed it) a cycloalkene. This double bond opens up a whole new world of possibilities in terms of nomenclature and reactions.

What you should know about alkenes

The first thing to learn about alkenes is naming them. The bad news is that there are new rules to learn since we introduced a new component to our molecule. The good news is there isn’t that much more to learn, and the majority of the rules for nomenclature are exactly the same. The main difference now is that the double bond will be the priority—over chain length and functional groups—in terms of naming the alkene.

Another important thing to note is how the double bond affects the geometry of the molecule. This would be another good time to break out the model kit to visualize this geometry in 3D. You should also note that a good way to identify an alkene, based only on the formula, is the number of hydrogens compared to the number of carbons—alkenes will have 2n hydrogen atoms, with n being the number of carbon atoms.

Make sure you are familiar with alkenes, because these will probably be the most important building blocks for the next sections of Organic Chemistry—the majority of reactions you will learn in this course will involve alkenes.

5 Curated Resources

This website gives a solid overview of all the basic things you’re going to need to know about alkenes including physical properties and a little bit about reactivity.

Alkene Nomenclature

free, Article

When double bonds are involved, you need to get more specific in reference to the physical location of substituents. New methods of naming come into play, and this article is a good summary of these rules.

E and Z Alkenes

free, Guide with practice questions

This is another site that talks about naming alkenes. This one deals specifically with E and Z nomenclature, which is a brand new topic unique to alkenes.

Alkenes and Alkynes

free, Video

Crash Course does a pretty good series on chem, and this is a good video explaining alkenes and alkynes. Alkynes come later in the course, so you can revisit this later on.


free, Article

Cycloalkenes can be a little tougher of a subject to grasp, and this site does a really good job of detailing everything you need to know. Plus, it’s got videos and activities that should help a lot.