EAS:Synergistic and Competitive Groups - Video Tutorials & Practice Problems

EAS with Polysubstituted Benzene

By now, we're really good at adding EAS reactions to unsubstituted Benzene by itself. And we're even pretty good at figuring out where to put the second group once you have the first one on there, when you react with a monosubstituted benzene. But what if you have 2 or more groups already on that benzene? Then what happens? Now there's going to be multiple new factors you have to take into account because now you have 2 or more groups. So this is called polysubstituted benzene. So when you have those 2 or more substituents, there are multiple new factors that you have to think about where to add that third, fourth, or fifth one. The first one is steric effects. Now that you have 2 or more groups, you may have some sites on that benzene that are completely unreactive due to the fact that they're between 2 sterically hindered groups. For example, the group between 2 tert-butyls like here, that position or the position between 2 rings like maybe a ring that's on the chain and a phenyl group, pH stands for phenyl, right? That wouldn't be very reactive. So these are sites that just would not react. They would literally be the very last site to react in an EAS reaction because all of the other sites are going to be more favored than that one. That's something you have to think about when you're using EAS, polysubstituted. You have to avoid those spots that are between sterically hindered groups. But guys, we also have directing effects because it turns out that the groups, now that you have more than 1, you have to consider the directing effects of all of them, not just one of them. The first type of effect that you could see is what's called synergistic groups, synergistic directing groups. That's when multiple directing groups all point to the same position. Here you notice that I'm adding Br 2 over FeBr 3 . This is going to be an EAS bromination. However, we've got an issue. We've got 2 groups already on this benzene. So, we have to analyze what are the directing effects of both of those. Nitro we know is a strong electron-withdrawing group. And OHC, what is that? Is that an alcohol? No, guys. You should know this from orgo 1. That is an aldehyde. We know that the CHO condensed formula stands for an aldehyde. So it's actually an aldehyde, so it's also a moderate withdrawing group as well. Then, we would expect these to both be meta directors. So the nitro group, I'm just going to draw its effects with a circle shape. So the nitro group is going to direct towards this meta position and this meta position. See how those are both meta to the carbon that it's on. And then the aldehyde is going to direct towards this meta position and this meta position because those are the ones that are meta to

Which is NOT a possible product of the reaction?

• A.
• B.
• C.
• D. All of them are possible products

Which is NOT a possible product of the reaction?

• A.
• B.
• C.
• D. All of them are possible products