Benzene Reactions - Video Tutorials & Practice Problems
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Benzene Reactions
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Now we've seen benzene a few times within this chapter. Now benzene itself is what we call an aromatic compound. And aromatic compounds have an unusually or uniquely stable condition. Benzene possesses Pi bonds, but because of its aromaticity and its unique stability, it doesn't undergo additional reactions like we would expect. Benzene undergoes substitution reactions instead, and that's unlike alkenes and alkynes which do addition, because they have pi bonds, but they're not uniquely stable. Now here we're gonna cover 2 types of substitution reactions that Benzenes undergo. One being Halogenation reactions, where we're substituting in a Halogen onto the Benzene ring, and then Friedel Craft Alkylation, We're substituting an alkyl group onto the benzene ring. So just remember, Benzene is pretty special. It's aromatic and very stable. It's gonna do substitution reactions instead of addition reactions, because it wants to maintain this very highly stable form that it possesses.
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concept
Halogenation Reactions
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In this video, we're gonna take a look at the halogenation of benzene. Here, benzene would react with either b r 2 or c l 2. In this reaction, one of the hydrogen atoms on the benzene is substituted with an x, which stands in for either bromine or chlorine. Here we'd say that a catalyst in a form of f e x 3, where x 3 is either Br 3 OR CL 3, must be used and has to contain the same halogen as the reagent. So basically what I mean by this is if x 2 here is c l 2, then this has to be FeCl3. If x 2 here is b r 2, then this has to be Febr 3. So if we take a look here at this Benzene halogenation reaction example, we have our Benzene with its 6 hydrogens on it. Remember, x here equals either bromine or chlorine. What happens is that one of these hydrogens gets replaced hydrogens gets replaced by this halogen here, one of them. And so here, the h is now gone, and instead in its place we put one of the halogens. That halogen could be chlorine or bromine. This is a way that we can substitute in a halogen at the expense of losing a hydrogen on benzene.
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example
Benzene Reactions Example
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Which of the following is a correct product of benzene substitution reaction with Br 2? So remember, here we have the bromination of benzene, where we're going to substitute out a hydrogen on benzene for a bromine. A doesn't work because we substituted in somehow an iron, which doesn't work. B doesn't work because we only substitute in 1 bromine, not 2. C doesn't work because the h is still there. The answer here is d because there was an H here, and we substituted it out to get the bromine there, creating bromobenzene as our answer. So here option D is the correct answer.
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Problem
Problem
Name the product of the following benzene halogenation reaction.
A
chlorobenzene
B
1,1-dichlorobenzene
C
1,2-dichlorobenzene
D
1,4-dichlorobenzene
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concept
Friedel Craft Alkylation
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In this video, we're gonna take a look at Friedel Craft Alkylation. Here in this reaction, Benzene reacts with an alkyl halide, And what happens is that one of the hydrogens on the Benzene ring is substituted with an alkyl group. To do this, a catalyst of Aluminum X3 must be used and has to contain the same halogen as the reagent. So basically what we mean by this, if we take a look at this Friedel Crafts reaction down below, this is CH three x. This x could represent either bromine or chlorine. If it's bromine, then this has to be a l b r 3. If this X is chlorine, then this has to be AlCl3. So the halogens have to match between these 2. Now, in this reaction all that happens is that one of the hydrogens on benzene gets substituted out, and the alkyl portion of our alkyl halide comes in. The alkyl portion of our alkyl halide here would be methyl, so we wind up making methylbenzene as our final answer.
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example
Benzene Reactions Example
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Name the major product of the following Friedel Crafts alkylation reaction. Alright. So here we have our Benzene, and we know we're still gonna have Benzene at the end, so we can redraw it. And we know that essentially what happens is, one of the hydrogens on Benzene gets substituted out with the alkyl group portion of my alkyl halide. So here we have Ethyl Chloride and we have Aluminum Chloride as the catalyst. So here, we're going to attach Ethyl to my Benzene. This would be my major product form, and its name would be Ethylbenzene. So just remember with Friedel Crafts alkylation, we're just substituting out an h and bringing in an alkyl group.
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concept
Summary of Benzene Reactions
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So here we have a summary of our benzene reactions. We have halogenation, in it we have the reagent of X2, which could represent Br 2 or Cl 2. We use our catalyst to get things going. In essence what happens is that we substitute out one of the hydrogens on benzene with one of these halogens here. If this is br 2, then this has to be Febr 3. If this is cl 2, then this has to be FeCl 3. At the end, the h is substituted out, the halogen comes in. Next, we have Friedel Crafts alkylation. Here we use as an our reagent in alkyl halide, x again could be CL or BR. But now we're using the catalyst of Aluminum, and it could be either Aluminum Chloride or Aluminum Bromide. Here, we substitute out our Hydrogen and bring in our alkyl group. Here if the X is Cl, then this is aluminum chloride. If the x here is bromine, then this is aluminum bromide. So remember, both of these reactions are quite similar, They use similar types of catalyst, and they're just substituting out an h. This one substitutes in a halogen. This one here an alkyl group.
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Problem
Problem
Provide a complete reaction of benzene Friedel Crafts alkylation with 2-bromo-2-methylpropane and name the product.
A
B
C
D
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Problem
Problem
Fill in the missing reagent for the provided reaction.
A
B
C
D
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