Organic Chemistry

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10. Addition Reactions

Alkyne Hydroboration

Hydroboration-oxidation of terminal alkynes leads to formation of aldehydes. (If the alkyne is not terminal, it will just yield a ketone). 



Anti-Markovnikov addition of alcohols to terminal alkynes yields aldehydes

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All right. So remember that we had three different ways at alcohol. We had hydration. We had Oxy, Mark. We had one more, and that was Hyderabad oration. Remember? What was kind of interesting about hydro gration was that it did everything opposite hydro operation is actually going to be anti Markov Nankov addition of alcohol. So what that means is that if once again, I have the blue site and I have the red site, which one is it gonna add to? Well, it would actually add to the less substituted position. So it ad right here. Okay, so once again, notice that I'm getting an eagle. I'm still getting a vinyl alcohol. The difference is that it's just in a different position. Okay, Now, notice my re agents really quick. Just noticed that I said ph three or on other boron source. That's because hydro operation there's a lot of different boron sources that your professors could use. So you just have to be aware of the one that your professor likes to use, okay? And then obviously the bottom part was the oxidation step. So I've got the Enel. How do I figure out what the product looks like same process. I'm going to switch the position of the double bond and the H. So what that means is that in my final product, what I'm going to get is now, instead of a double bond there, I'm just gonna get a single bond. And instead of a single bun to the oh, I'm gonna get a double one to the O. Okay. So what this means is that where did the extra h go? The extra h went here? Because right now there was only one h here. And now there's gonna be two ages. There's that original age. And then there's that extra age that extra blue H whatever. Was this a trade here and it transferred. Okay, so now notice what kind of molecule this is. I just drew a terminal carbon Neil, This actually has ah hydrogen at the end. This is actually going to lead to the formation of Alba hides. Okay, so when you do a Markov knockoff edition of water, that's gonna be a key tone product. Okay. When you do an anti Markov knockoff edition of water, where you're gonna lead to is an anti Markov nick off alcohol or Enel, which then turns into an alga hide. Now, notice that in general this is still called the Keto form. Okay, if you were to say just in terms of Todd Immers, this is the anal totem. Er, this is the Keto totem. Er, but this specific molecule happens to be an alga hide because the carbon is right at the edge, and it has one h on it. Okay, so just something that you guys need to be aware of. It's something that could definitely come up. So you guys just need to know what's going on. All right? So I hope that made sense. Let me know if you have any questions.

This reaction yields an anti-Markovnikov vinyl alcohol, which will tautomerize into a carbonyl on the terminal position, which is the definition of an aldehyde.