Show the major product(s) from reaction of the following substances with (1) CH3 CH2 Cl, AlCl3 a

Show the major product(s) from reaction of the following...

Key Concepts

Friedel-Crafts Alkylation

This reaction involves the substitution of an aromatic hydrogen with an alkyl group through the use of an alkyl halide and a Lewis acid catalyst such as AlCl3. The process proceeds via the formation of a carbocation or a complex that acts as the electrophile, which then attacks the aromatic ring in an electrophilic aromatic substitution mechanism. The reaction is essential in organic synthesis for constructing carbon–carbon bonds on aromatic systems.

Electrophilic Aromatic Substitution (EAS)

EAS is a fundamental reaction mechanism in aromatic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. The stability of the aromatic ring is temporarily disrupted during the formation of a sigma complex and then restored after deprotonation. This mechanism underpins many important reactions in organic chemistry, including halogenation, nitration, sulfonation, and Friedel-Crafts reactions.

Electrophilic Aromatic Nitration

This nitration reaction involves treating an aromatic compound with a nitrating mixture of nitric acid and sulfuric acid, which generates the nitronium ion (NO2+). The nitronium ion acts as a strong electrophile that undergoes electrophilic aromatic substitution, attaching a nitro group to the aromatic ring. This type of reaction is widely used to introduce nitro substituents onto aromatic systems, which can then be further modified in subsequent reactions.

Carbocation Formation and Stability

Central to many electrophilic aromatic substitutions, particularly Friedel-Crafts alkylations, is the generation of a carbocation intermediate. The stability of this carbocation is crucial for the reaction to proceed, influencing the reactivity and selectivity of the electrophilic attack on the aromatic ring. Rearrangements may occur if a more stable carbocation can be formed, affecting the nature and position of the substituents on the final product.

Directing Effects in Aromatic Substitution

Substituents already present on the aromatic ring can significantly influence the position at which new substituents are introduced. These groups can be activating or deactivating and can direct incoming electrophiles to ortho, meta, or para positions based on their electron-donating or electron-withdrawing properties. Understanding these effects is essential for predicting the outcomes of multiple substitution reactions on aromatic compounds.

Transcript

00:01 All right.

00:01 So we're given two die substituted benzene's again with some schemes.

00:07 And we just got to predict where the site of reaction is going to happen.

00:13 Which position is that substitution going to happen at? so keep in mind that it's not the reaction, the reaction of the next substitution reaction that's going to dictate where the substituent goes.

00:28 It's what's already on the ring.

00:29 Right.

00:30 So in this case, you can look at this, this orthobromotolune, and you can say, okay, so they're both orthoparad directors.

00:40 The alchal group is a stronger director than the bromine, although they're both orthopara.

00:46 Right.

00:46 So you probably say the methyl group would want to direct here and here the bromine would want to direct here and here.

00:56 But as i said, the methyl group is the stronger.

00:59 Director, so you'd probably favor substitution at either of the sites that the methyl group is directing you to.

01:05 So really, the methyl group is the major director here.

01:09 And we're doing a freedlcraft's alkylation.

01:11 So we have ethyl chloride with aluminum chloride as the lewis acid catalyst.

01:19 So you're going to get a mixture of this product.

01:25 And then you're going to get a mixture.

01:28 The other component is likely going to be.

01:31 The one that's para to that.

01:33 So you're adding an ethel group, right? so between these two products, i would say you're probably going to have a small excess of this one, only because that ethel group is going to have free rotation.

01:43 And you see some steric blocking here where you have if the ethohroup chs and the methyl group chs are colliding, it's probably going to favor the para position substitution.

01:55 While still being a mixture of orthopower, you're probably going to favor the para as the major product, among the major products, right? something else, the textbook doesn't really say this, but you know that the products of alkalations are more active than the starting material because that alkyl group is going to activate.

02:15 So just as a fun exercise, you might even see some products of, let's say, this paris substituted products.

02:23 Now the positions here and here are going to be more activated because now you have an ethel group directing to those sites.

02:32 So you might even see, for example, it's going to be pretty sterically encumbered, but you might even see some tetra -substuted benzene form if you get a second alkylation on the already alkylated set of products because you know that that can happen with alkylations.

02:51 So just a thought experiment...

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