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Topic: Rank bromination of arenes from fastest to slowest?  (Read 6137 times)

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Offline UpbeatWhiz

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Rank bromination of arenes from fastest to slowest?
« on: February 07, 2012, 06:53:06 PM »
Hey guys I am having a hard time ranking these from fastest to slowest for my organic chemistry lab and was wondering if you could help me out.

Toluene
Anisole
Diphenyl Ether

In the lab when we actually did it observed that the rates were(from fastest to slowest): Diphenyl Ether, Touene and then anisole but I think theoretically our results should be different?

If anyone could help me out I'd really appreciate it!

Thanks :D

Offline Dan

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Re: Rank bromination of arenes from fastest to slowest?
« Reply #1 on: February 07, 2012, 07:54:24 PM »
Think about Coulombic attraction - this is the heart of organic chemistry.

+ attracts -; electrophiles react with nucleophiles.

Consider your reagents. Are your arenes reacting as nucleophiles or electrophiles? Is the brominating agent an electrophile or a nucleophile?

Nucleophiles are more reactive if they are more electron rich (more negative) and elecrophiles are more reactive if they are more electron deficient (more positive). How does this translate to your series of arenes?
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Offline UpbeatWhiz

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Re: Rank bromination of arenes from fastest to slowest?
« Reply #2 on: February 07, 2012, 09:11:26 PM »
Think about Coulombic attraction - this is the heart of organic chemistry.

+ attracts -; electrophiles react with nucleophiles.

Consider your reagents. Are your arenes reacting as nucleophiles or electrophiles? Is the brominating agent an electrophile or a nucleophile?

Nucleophiles are more reactive if they are more electron rich (more negative) and elecrophiles are more reactive if they are more electron deficient (more positive). How does this translate to your series of arenes?

Bromine is a nucleophile in this case I believe.

So would it be:

Anisole
Diphenyl
Toluene

What confuses me is that we did not observe that when actually conducting the experiment in the lab (Diphenyl Ether, Toluene, and then anisole), is there a reason for that. Maybe the temperature or the some condition in the lab wasn't right?



Offline Dan

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Re: Rank bromination of arenes from fastest to slowest?
« Reply #3 on: February 08, 2012, 03:30:07 AM »
Bromine is a nucleophile in this case I believe.

So would it be:

Anisole
Diphenyl
Toluene

Can you explain your logic for all of this. Think about the mechanism, the curly arrow starts from the nucleophile.
My research: Google Scholar and Researchgate

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