Rank the compounds in each group according to their reactivity toward electrophilic substitution

step 1 All right. So there are four parts of this problem. We're going to rank these compounds in order

Rank the compounds in each group according to their...

Key Concepts

Directing Effects

Substituents on an aromatic ring not only affect reactivity but also direct the incoming electrophile to specific positions (ortho, meta, or para). Activating groups generally direct the electrophile to the ortho and para positions, while strong deactivating groups direct the reaction primarily to the meta position due to the maintenance of relative stability in the transition state.

Resonance Effects

Resonance effects involve the delocalization of electrons, where substituents can either donate or withdraw electron density through conjugated pi systems. In electrophilic substitution reactions, substituents that participate in resonance donating typically enhance reactivity, whereas resonance withdrawing groups diminish reactivity by stabilizing electron deficiency in the ring.

Inductive Effects

This refers to the electron-withdrawing or electron-donating influence exerted by substituents through sigma bonds based on differences in electronegativity. In electrophilic aromatic substitution, substituents with strong inductive withdrawing effects reduce reactivity by pulling electron density away from the aromatic ring.

Electrophilic Aromatic Substitution

This is a reaction mechanism in aromatic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. The reaction involves the formation of a non-aromatic carbocation intermediate, which is then deprotonated to restore aromaticity, making the process sensitive to the nature of the substituents already present on the ring.

Substituent Effects (Activating and Deactivating Groups)

Substituents on an aromatic ring influence the rate and orientation of electrophilic aromatic substitution. Electron-donating groups tend to activate the ring by increasing its electron density, thereby facilitating electrophilic attack, while electron-withdrawing groups deactivate the ring by reducing electron density, decreasing its reactivity towards electrophiles.

Transcript

0:00 All right.

00:01 So there are four parts of this problem.

00:02 We're going to rank these compounds in order of their reactivity to electrophilic substitution.

00:09 There was a question like this in the chapter.

00:12 It's a slightly more difficult.

00:14 Right.

00:14 So we're going to go ahead and start with three in a.

00:20 So we have chlorobenzene.

00:22 We have dichlorobenzene.

00:24 And we have regular benzene.

00:26 Right.

00:26 So i'm going to do, i'm going to number one.

00:31 One being the slowest and three being the fastest is going to be my key here.

00:41 There's your legend.

00:44 So if you look at the three options we have here, right? so we're just look at all the substituents.

00:49 Obviously, benzene is going to be your standard, right? that's when you have h as a functional group or a substituent, right? versus one chloro, which is a slight deactivator of the ring, and you have two chlorines, which is going to be twice as deactivating as, well, i shouldn't say that, but you're going to have an additional substituent that's going to contribute to the deactivation of the ring.

01:14 So it's safe to say that dichlorobenzene is going to be slower than regular monochloral benzene, and then both of those are more deactivated than regular benzene.

01:26 So benzene in this case is going to be your fastest because you have mono and dichlorobenzene.

01:33 Which are both deactivated.

01:35 So a similar situation with b here, right? so you have, in this option, you have parabromo nitrobenzine.

01:43 So you have two deactivating groups.

01:45 In this substrate, you have one deactivating group compared to phenol, which is an activating group.

01:50 So it's pretty safe to say that you're going to have phenol being the fastest in this case.

01:56 So which is more deactivating, having a nitro group by itself or having a nitro group? and a bromine.

02:04 So bromine is going to add more deactivation to the ring than having, so nitro plus bromine on the same ring is going to be a more deactivated ring than just nitrobenzine because the bromine is going to deactivate that ring a little more.

02:23 So nitrobenzine is going to be faster than parabromo nitrobenzine for sure.

02:30 Oh, that's a three and that to be a one, sorry.

02:32 That's the slowest.

02:35 On to the next problems, right? so you have fluorobenzene, benzaldehyde, and orthozylene.

02:42 So xylene is dimethylbenzine, right? so they're ortho -to -which -to -ach other.

02:46 It doesn't matter.

02:46 The methyl groups are both activating...

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