Arrange the following groups of compounds in order of...

Arrange the following groups of compounds in order of decreasing reactivity toward electrophilic aromatic substitution: a. benzene, ethylbenzene, chlorobenzene, nitrobenzene, anisole b. $1-$ chloro- 2,4 -dinitrobenzene, 2,4 -dinitrophenol, 2,4 -dinitrotoluene c. toluene, $p$ -cresol, benzene, $p$ -xylene d. benzene, benzoic acid, phenol, propylbenzene e. $p$ -nitrotoluene, 2 -chloro- 4 -nitrotoluene, 2,4 -dinitrotoluene, $p$ -chlorotoluene f. bromobenzene, chlorobenzene, fluorobenzene, iodobenzene

Arrange the following groups of compounds in order of decreasing reactivity toward electrophilic aromatic substitution:
a. benzene, ethylbenzene, chlorobenzene, nitrobenzene, anisole
b. $1-$ chloro- 2,4 -dinitrobenzene, 2,4 -dinitrophenol, 2,4 -dinitrotoluene
c. toluene, $p$ -cresol, benzene, $p$ -xylene
d. benzene, benzoic acid, phenol, propylbenzene
e. $p$ -nitrotoluene, 2 -chloro- 4 -nitrotoluene, 2,4 -dinitrotoluene, $p$ -chlorotoluene
f. bromobenzene, chlorobenzene, fluorobenzene, iodobenzene

Key Concepts

Resonance Effects

Resonance effects involve the delocalization of electrons through conjugated systems within the aromatic ring. Substituents that can engage in resonance with the ring can either stabilize the intermediate complex formed during electrophilic aromatic substitution or alter the electron density distribution, influencing both reactivity and regioselectivity.

Inductive Effects

Inductive effects pertain to the electron-withdrawing or electron-donating properties of substituents through sigma bonds. These effects alter the electron density on the benzene ring by shifting electrons toward or away from certain regions, thereby affecting the overall reactivity of the aromatic system in electrophilic substitution reactions.

Activating and Deactivating Groups

Activating groups are substituents that donate electrons to the aromatic ring, enhancing its reactivity toward electrophiles, while deactivating groups withdraw electrons, thereby reducing reactivity. The relative strengths of these groups determine the overall rate of electrophilic aromatic substitution and the preferred positions for substitution.

Electrophilic Aromatic Substitution (EAS)

EAS is a fundamental reaction mechanism in aromatic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. This process generally involves the formation of a positively charged sigma complex, followed by deprotonation to restore aromaticity. The reactivity of the aromatic system in EAS is greatly influenced by the substituents present on the benzene ring.

Substituent Effects

Substituent effects refer to the influence that attached groups exert on the reactivity and orientation of subsequent reactions in aromatic systems. These effects are manifested through changes in electron density on the benzene ring, affecting both the rate and regioselectivity of electrophilic aromatic substitution reactions.

Transcript

00:01 We're going to order the reactivity of some benzene derivatives.

00:09 Okay, so starting up, we have regular benzene.

00:13 I'm just going to list out the substituents here.

00:16 So if we have h and ethyl, okay, then the chloro group, a nitro group, and demethoxy.

00:28 Okay, so that's actually quite a bit, but we know actually that.

00:34 Hydrogen or the benzene will most likely be in between since we're going to have some activating groups that will give it higher activity and deactivating groups that give benzene lower reactivity.

00:47 So here we can see there are actually only two activating groups, with the methoxy being stronger than the ethyl.

00:57 And then we have two deactivating groups with the nitro being more deactivating than the clothexivating.

01:03 Then the chloro, okay, and the benzene is in between.

01:08 Okay, so we're going to put the reactivity.

01:14 It will be here, here, here, and there.

01:18 Okay, so there we have one.

01:23 Okay, next up we are going to have, okay, here we're going to show it.

01:33 So we have one, chloro, two, four, dinitro, followed by phenyl dinitro.

01:54 Then we also have a thaluvine dinitro.

02:00 So then the dinitro and its position is common in all of these three benzene.

02:07 Okay, so now we're just left to look at the other substituents here on the one position.

02:15 Okay, so we know that the hydroxyl is actually, it has lone pairs, just like the methoxy that's able to donate to loan pairs and to be a very good, you know, activating group, and that could at least cancel out one nitro group.

02:32 Okay, well, the methoxy is a weak activating group, and the chloro is the weak deactivating group.

02:40 So that will actually allow us to place this.

02:43 It's most reactive, pulled by the m for the tal uvein, and the three for the chloral.

02:51 And that's just now looking solely at the subsistuient on the one position.

03:01 Okay, next step.

03:04 We have tal uine.

03:07 So here, we have to also draw the full things.

03:12 We have tall uvein.

03:13 A kressol.

03:15 So kressol is toluene again, but now alcohol, all for alcohol, followed just by benzene, which i just call h, and then a parasylene...

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