100 Nano-Stories: Naming Alkenes!
Episode #38: Follow-Along Alkene Examples!
Preface! → ✨
It’s your favorite material science & nanotechnology enthusiast! Yesterday, I made an introductory article on alkenes & alkynes! These names are essentially double and triple bonds between carbon atoms in an organic compound/chemical. Check out the introductory article below! :)
But for today’s topic, we will discuss how to name alkenes!
Note: I was planning to name both alkenes & alkynes in this article, but there are so many examples for both of them, it’s better to fully explain the double and triple bonds in separate articles. Cheers! ✌🏽
Alkene Examples! → 😤
Example 1! → 🔑
This alkene is called ethene. But why ethene? If you remember the names we used when we named alkanes, ethane was used for two carbon atoms that are single-bonded together.
But alkenes have double bonds, not single bonds. So all we do in this situation is change the suffix from “ane” to “ene”.
The final answer is ethene! 🔑
Example 2! → 🔑
Let’s try something a bit more complicated, reader!
The first step is to ignore the hydrogen atoms when naming the alkene. You only name alkanes, alkenes, or alkynes by the bonds between the carbon atoms.
The next step in this situation realizes that there are more than 2 carbon atoms. Because of this, we have to use numbers to try and find the lowest number that we can give to the double bonds between the carbon atoms.
If we count from the carbon atom from the far right, we get the carbon double-bond as carbon #2. But if we count the carbon atom from the far left, we get the carbon double-bond as carbon #1.
The correct way to write the number of the double bond in the alkene is with the double-bond having the carbon number as 1!
The next step is to know the name of the organic molecule just by looking at the carbon atoms. There are 3 carbon atoms, and if we remember from naming alkanes, the name for an alkane with 3 carbon alkanes is propane. But because this contains a double-bond (alkene), we change the suffix from “ane” to “ene”. Propane → Propene.
The final step in this problem is how to properly name the molecule. The name of the molecule is propene, and the number of the propene molecule is 1.
When naming an alkene, we add the prefix name first, then the number of the molecule, and then the suffix name.
To name this molecule, we add the prefix name (prop), then the number (1), and then the suffix name (ene.)
The answer to this molecule is prop-1-ene! 🔑
Example 3! → 🔑
Now it’s time for the last example! Time to test your new knowledge of alkenes!
The first step in this situation is to find the longest carbon chain possible!
In this case, the longest carbon chain has already been given to you in the correct order and from the right direction. The double-bond is closer to #1 from the right than from the left. You got lucky this time. . . but not next time. 😈
Anyways, the next step is to name the longest carbon chain. In this case, the longest carbon chain is 6 carbon atoms long. From our alkane naming, this is hexane.
The next step is to name the substituents by their proper number & suffixes. Substituents are carbon atoms that are not part of the main carbon chain and are connected to the main carbon chain.
The substituent at Carbon #4 has two carbon atoms, and because it is not part of the main carbon chain, it is called “4-ethyl”. “yl” is the proper suffix when naming a substituent.
The substituent at Carbon #2 has one carbon atom, and because it is not part of the main carbon chain, it is called “2-methyl”.
The final step is to name the entire molecule! From our alkane naming, the main carbon chain goes last! The substituents go first, but “4-ethyl” goes first because it is not connected to the double-bonded carbon in Carbon #1 and #2.
“4-ethyl” goes first. Next is “2-methyl”. (4-ethyl-2-methyl). Next, we include the main carbon chain name and the lowest number/location of the double-bond. In this example, it is a hexene. But because of the location of the double bond, the number is 1.
To name the end of this molecule, we add the prefix name (prop), then the number (1), and then the suffix name (ene.) We end up with “hex-1-ene”.
Our final answer is (4-ethyl-2-methylhex-1-ene)! 🔑
Closing Thoughts! → 💭
We did it! Now you know a bit more about naming alkenes! Noticing the similarities between alkanes, alkenes, alkynes will eventually make naming the molecules and organic compounds a lot easier! Stay tuned for how to name alkynes! ✌🏽
Vocabulary! → 📓
Alkane → An organic compound that is only made out of carbon & hydrogen atoms, only single covalent bonds.
Single-bond → There is two electrons (or one pair) being shared between two atoms.
Double-bond → There is four electrons (or two pairs) being shared between two atoms.
Alkenes → Double Bonds occur between carbon atoms in a molecule in organic chemistry.
“yl”/moieties → A substituent, or chemically bonded parts of molecules attached to a larger backbone/ring. Essentially, it is not part of the main carbon chain.
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