Organic Chemistry

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16. Conjugated Systems

Stability of Conjugated Intermediates

Regardless of the type of reactive intermediate, conjugation increases the stability.



Stability of Conjugated Intermediates

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Now let's focus on the specific intermediates that conjugation hopes to stabilize. So regardless of the type of intermediate you are, whether you're a carbo cat iron or a carbon ion, the ability to resonate is always gonna make you more stable. But as we learned from prior lessons in organic chemistry, one residents doesn't affect all intermediates equally, some intermediates benefit more from residents, and some intermediates benefit less weaken. See this with the trends of Carvel, Catalans versus Radicals. What we see is let's start with the first one Carbo Catalans. We see that obviously primary carbo Catalans are terrible. And as we add our groups, this will be primary, secondary tertiary as we add our our groups to become more stable, that should make sense with everything else. You've learned about Carbo Karan's thus far. But notice that we have these Carvel cannons in the middle that are both primary, right? So I included these primary carbo Catalans. But what's the difference now You know that these air conjugated thes air conjugated primary Carvell cabins. As you can see, they haven't least three atoms that could resonate in a row, so this would be called primary a Lilic, and this would be called Primary Ben's Ilic. Okay. Either way, both of these were going to be more stable than a typical primary because of their ability to resonate. Now, if we look at the same trend for radicals, we notice a similar pattern, which is that as you add our groups, they become more stable. And as you add conjugation, they become more stable. Okay, however, there's a big difference. Which is that for Carbo Catalans? We tend to say that hyper conjugation or the addition of our groups is actually going to be the best thing for a carb Acadian if you have a tertiary Carl Cadogan that is the most stable. Whereas for radicals, radicals are actually the most stabilized by resonance, meaning that a Lilic and Ben's Ilic positions are truly ideal for radicals to exist because that's the most stable type of radical that you can get. Okay, so regardless of the type of intermediate, it's always gonna make it more stable. But as we compare and contrast Carbo Karen's versus Radicals, we see that radicals benefit even more from conjugation than a typical carbon Catalan. Would that being said, the stability of the Olympic position is gonna open up reactions toe happen at that location that are radical and carbon cattle and intermediate it. And we're going to see that as a general pattern. That thes, um, intermediates love to form on that a Lilic position due to the congregation that they can achieve. So I'm just going to show you guys to really brief examples before we get into the specific types of reactions. But as you can see, imagine that you have a radical in the Olympic position and a radical re agent You could see a termination step occurring, right, a termination step that would then take these two radicals from Sigma Bond. And we would get a product that looks something like this, right? Another possibility would be, Well, what if you had a carbo cat? I inform on that a little position and directed it with something negatively charged. Or let's just say with available lone pair, Well, then you could get just basically a nuclear feel like attack on that reaction site. So then we would form actually pretty much the same exact compound in this case just due to two different mechanisms, so thes air not reactions for you to memorize. I'm really just trying to introduce the idea that we're always going to be watching out. Now that we understand it. We're always gonna be watching out for this a Lilic position. Because if we conform a reactive intermediate in that position, it's highly likely to react with another re agent. And I'm gonna wind up getting reactions at the Olympic position where the double bond remains. But now I have a new Adam attached to that. A little position. All right, so let's all for this topic. Let's move onto the next one.

     1. Carbocations


     2. Radicals