as you may recall, last blog we talked about the wonderful world of alkanes. But it was a little plain, no? Now you have the chance to spice it up a little bit with adding in a few doubles bonds here, and a few triple bonds there. Let's start off with a few definitions:
Alkene: An organic compound containing a double bond between two carbons.
Alkyne: An organic compound containing a triple bond between two carbons.
Now we've established the difference between those two, we can get down to business.
This is an alkene. Note the double bond.
How to name alkenes? You would name it just like alkanes, except changing the -ane to a -ene. For example, in the above image, there are two carbons. If you were writing an alkane, it would be ETHANE. However, because of the double bond, it is an alkene. Thus, the name for the above compound would be ETHENE.
Drawing them is a different matter. "How would we know where the double bond goes?", you may ask. Here is a better example to work with than the above:
Meet hexene. As you can see, his double bond is in the middle of the schmongle. Recall how to write alkanes. Note that the carbon with the double bond is the 3rd one from the left/right. So we wouldn't have to bother with worrying about the smallest number. Since the double bond is on the 3rd carbon, we would name this 3-hexene. So drawing them would be the same matter. Just the corresponding number to where the double or triple bond is.
Now meet ethyne. Ethyne is an alkyne. How do we know? See that triple bond there basking in it's glory? That's how we know.
Dealing with alkynes may look exhausting because of the triple bond, but do not fear. You'd be glad to hear that you do exactly what you've been doing all along with alkanes and alkenes. Just always, ALWAYS, remember to label where the triple bond is.
TMFAQ (The Most Frequently Asked Question)
Promising title isn't it? But the question is: What if we have a branch AND a double/triple bond?! What do I do with the naming? Would the branch be a priority for the "lowest number" used in describing the compound or would I use the location of the double/triple bond and then do things accordingly?! SAY WHAT?
Calm down, my young disciples. If something looked like this:
You will ALWAYS, prioritize the double bond first. Same with triple bonds (alkynes). THEN, you do things accordingly. Therefore, this would be 2-methyl-3-hexene.
Calvin's take on "OChem"...