At what position, and on what ring, would you expect bromination of benzanilide to occur? Explai

step 1 Okay, so we're working with benzeneylyde here. You'll notice that there are two rings. So we hav

At what position, and on what ring, would you expect...

Key Concepts

Electrophilic Aromatic Substitution (EAS)

This reaction mechanism involves the attack of an aromatic pi system on an electrophile to form a arenium (sigma) complex intermediate, which then loses a proton to regenerate the aromatic system. Understanding the steps of EAS is crucial since it explains the formation of sigma complexes, the role of substituents in stabilizing or destabilizing the intermediate, and how reaction conditions influence regioselectivity.

Substituent Effects in Aromatic Systems

Substituents on aromatic rings can either donate or withdraw electron density through resonance or inductive effects. These effects determine the overall reactivity of the ring toward electrophilic aromatic substitution and direct the electrophile to specific positions (ortho, meta, or para) on the ring. In many systems, electron-donating groups activate the ring and favor ortho/para substitution, whereas electron-withdrawing groups deactivate the ring and often lead to substitution at the meta position.

Resonance Contribution of Amide Groups

Amide groups display significant resonance stabilization because the lone pair on the nitrogen can delocalize into the carbonyl group. However, when the nitrogen is attached to an aromatic ring, this delocalization influences the directing effects and reactivity of that ring. The partial donation from the nitrogen can activate specific positions on the aromatic ring, making them more susceptible to electrophilic attack even if the overall donation is moderated by the adjacent carbonyl.

Transcript

00:02 Okay, so we're working with benzeneylyde here.

00:05 You'll notice that there are two rings.

00:07 So we have to determine which ring and at what position on that ring would bromination occur at.

00:14 So it doesn't matter which electrifier we're adding.

00:15 It matters what we're dealing with what substituents are already on the ring.

00:20 So let's take the ring on the left first.

00:23 The ring on the left only has one substituent and there is a carbonyl on the carbonial on the carbon that's right next to the ring.

00:28 Therefore we're going to have a strong electron withdrawing group on that ring.

00:33 This ring is going to be deactivated because of that carbonyl group.

00:37 So we're off to a good start.

00:40 The ring on the right, even though it is bridged by this carbonyl containing group, the carbonyl isn't adjacent to the ring.

00:51 And that makes a huge difference about the electronics of that ring.

00:55 In fact, because the nitrogen is the group that is, adjacent to the second ring on the right, you actually have an electron donating effect from that nitrogen.

01:07 So although this carbonyl is going to be electron withdrawing overall, you do get some degree of stabilization from the lone pair on that nitrogen.

01:18 So it's somewhat equivalent.

01:20 It's not as good.

01:21 Let's say this was a methyl group instead of a carbonyl.

01:24 The ring on the right would be more activated...

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