I hope you guys gave this a fair shot because this is also a very common synthetic pathway. You should know by the end of this lesson how to turn trans into cis and cis into trans. That's a huge part of this chapter. So let's go ahead and get started. Since there's no way to directly turn this into one or the other, I'm going to need to go to the triple bond first. I'm going to need to take it up to a triple bond and then I can hydrogenate it to whatever type of double bond I want. So if I'm making this a triple bond, then I'm going to start off with a diatomic halogen again. Let's try Cl₂ this time. What that's going to do is it's going to give me vicinal dihalides. Okay? Then my second step is going to be to make this into a triple bond, and I can do that using one of my strong small bases in excess. Now notice that this is not a terminal triple bond. What this is going to make is actually an internal triple bond where the triple bond is inside of 2 different carbon groups. So could I ever get an alkynide out of this? Remember, an alkynide has that negative charge. No. Because this doesn't even have a hydrogen to remove. There's no hydrogen here. So when I take my base in excess, I'm just going to end at the triple bond. I'm not going to go all the way to the alkynide. Okay? So now I have that triple bond. What could I do to make that into a cis double bond? It's not that hard. All I have to do is use Lindlar's catalyst.

Okay and there were a whole lot of other ways to write it. I'm going to let you guys look that up depending on what your professor wants. But I'm just going to write 'Lind Lars' because that's another acceptable way to write it.

Okay, and it would be 'Lind Lars' and H₂. H₂ and Lind Lars. And what that's going to give you is that's going to turn that into a cis double bond, and now you've just made the conversion from trans to cis.

And now, you guys should for practice, really before you get to your exam, should know how to go the other way as well, to go from cis to trans. It's not that hard. Okay? So I hope that made sense to you guys. This is just a small taste. At the end of the day, you're going to have to practice, you're going to have to do homework, but I'm just trying to show you, give you hints of stuff that I've seen come up over and over again, and stuff you absolutely can't get to your test without knowing how to do. All right? So let me know if that helped, and let me know if you have questions. Let's move on.