Draw the resonance structures for the intermediate formed by substitution of anisole at the orth

Draw the resonance structures for the intermediate formed by...

Key Concepts

Mesomeric Effect

The mesomeric (or resonance) effect refers to the ability of substituents to either donate or withdraw electron density through pi-bond interactions. This effect is important in systems where substituents stabilize reaction intermediates by delocalizing positive charge, thereby playing a critical role in determining the rates and outcomes of electrophilic aromatic substitution reactions.

Substituent Effects and Directing Groups

Substituents attached to an aromatic ring influence both the reactivity of the ring and the position at which substitution occurs. Electron-donating groups, through their ability to donate electron density, activate the ring and direct electrophilic attack to ortho and para positions, significantly affecting the formation and stabilization of intermediates.

Resonance Structures

Resonance involves drawing multiple valid Lewis structures to represent the delocalization of electrons in a molecule. This concept is crucial for understanding how charge is distributed in intermediates, as the real electronic structure is a hybrid of these forms, which helps explain the stabilization of reactive species.

Electrophilic Aromatic Substitution (EAS)

EAS is a reaction mechanism where an electrophile replaces a hydrogen atom on an aromatic ring. This process involves the formation of a carbocation intermediate (often called the sigma complex or arenium ion), where the aromaticity is temporarily lost and then restored in the final step, making it essential for understanding aromatic reactivity.

Transcript

00:01 Okay, so this is a question that talks about the resonance forms of a nitrated benzene upon reaction with a second electrophile.

00:12 So the last few pages before this question in the textbook on page 589 shows you the orthopara and meta intermediates, carbocana intermediate, it's based on what, based on what substituent you have on the ring already before you undergo nitration.

00:37 And it cues you into what kind of things you should look for to denote something as being the least stable residence form or the most stable residence form.

00:49 So we're going to go through some of those here.

00:53 Now you know that nitration or that nitro groups are meta directing, right? so you're going to see something that would deter addition at ortho and parapositions that you won't see with meta.

01:11 So we're going to do ortho and power first just so i can get that point across.

01:14 So i'm going to do my hour portion in red.

01:16 So you're just going to take those double bonds.

01:18 You're going to rotate them in the ring.

01:22 So now we have this with your carbocat ion at this position over here, right? and now i can move that one more carbon over.

01:46 So now you have this.

01:47 Not wrong.

01:49 It's really easy to mess up these arrows.

01:52 No, that's right.

01:53 I'm not going crazy.

01:54 Right.

01:54 But the issue with, so we've arrived at the problem child.

01:59 Right.

01:59 So these are the three main ones, right? so you'll notice that, so you know with carbocations, they like to be stabilized by electron groups that are willing to share or donate their electron density.

02:17 Right.

02:17 So that's why carbocadions that have other carbons around it, like tertiary carburecabions are more stable than secondary for things like hypochonjugation and stuff like.

02:30 That right so same reason here except the reverse reasoning right so having a carbacallion directly on the same atom the same carbon atom as a nitro group which is one of the more strongly deactivating strongly electron withdrawing groups known to chemistry known to chemists it's going to seriously destabilize the intermediate and therefore being that the resonance form is kind of like an average of all contributing residence structures, right? so this guy here is going to be your least stable, your highest in energy, which is going to deter addition of the electric file at the ortho position because of the contribution from this residence form where you have the strong electron donating group on the same atom as your carbocation.

03:22 So you'll notice with the para, all i have to do is move the double -bondi, over one and you're going to arrive at the analogous high energy intermediate here.

03:44 Boom, right there.

03:47 So same deal there...

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