Predict the major product(s) of nitration of the following substances. Which react faster than b

Predict the major product(s) of nitration of the following...

Key Concepts

Activation and Deactivation

Activation or deactivation of an aromatic ring is determined by the overall electron density influenced by existing substituents. Electron-donating groups activate the ring (making it more reactive than benzene), while electron-withdrawing groups deactivate the ring (making it less reactive). This concept is critical in predicting the relative reaction rates of various substituted benzenes compared to benzene itself.

Directing Effects

Directing effects arise from the substituents on the benzene ring that influence the position where a new substituent will be introduced during electrophilic aromatic substitution. Activating groups generally direct incoming electrophiles to the ortho and para positions, while deactivating groups tend to direct them to the meta position, based on the stabilization of the intermediate carbocation.

Electrophilic Aromatic Substitution (EAS)

EAS is a fundamental reaction mechanism in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. The process involves formation of a sigma complex (an arenium ion), followed by deprotonation to restore aromaticity. Nitration is one common example of EAS, where a nitro group is introduced into the aromatic system.

Nitration Reaction

Nitration is a specific type of EAS where a nitro group (-NO2) is introduced onto an aromatic ring typically using nitric acid and sulfuric acid as reagents. This reaction is sensitive to the electronic nature of substituents already present on the aromatic ring, which can either accelerate or decelerate the reaction relative to benzene.

Substituent Effects

Substituent effects refer to the electronic influence exerted by groups attached to the aromatic ring. These effects, which include electron-donating or electron-withdrawing influences via resonance or induction, modify the reactivity of the ring towards electrophilic attack. Activating groups, typically electron-donating, increase the ring's electron density, while deactivating groups, usually electron-withdrawing, reduce it.

Transcript

00:01 Okay, so question 16 .29, we have to predict the nitration products of these six reactants, and then which reacts faster than benzene and which reacts slower than benzene.

00:14 So pretty general with the latter part of that question, a pretty general answer.

00:19 If there is a deactivating group on the ring, it's going to react slower than benzene.

00:23 If there's an activating group, it's going to react faster than benzene, if there's an activating group.

00:29 So that pretty much handles that.

00:32 And i'll say it again as i'm doing these, right? but it's basically just making the connection between ortho -paradirectors and meta -directors.

00:47 Right, i forgot the other name of that.

00:49 So let's get started, right? so you have bromobenzene here.

00:53 Bromene is an ortho -paradirector.

00:55 So you're going to get probably a mixture of the ortho -nizuretic.

01:00 Nitration product and the para nitration product probably favors the para position just because you might have some steric strain between the nitro group and the bromine group.

01:37 All right.

01:38 On to b.

01:40 So we're going to look at cyanobenzene now.

01:44 So cyanobenzene is a strongly deactivating group.

01:49 It's also a meta -director.

01:51 So that's going to cue us, well, why did that happen? that's going to cue us into the product here, right? so we're going to draw our little hexagon.

01:57 There we go.

01:58 Meta -director, we'll put it down here.

02:03 Same thing with c, right? well, really c and d and e are all pretty much the same.

02:09 So they're all deactivating groups, and they're all going to put the nitro.

02:17 Sorry, i forgot the arrow.

02:18 They're all going to put the nitro group meta to whatever substituents already there...

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