Organic - Odyssey number 36 Carbonyl compounds

[Mrhyde]

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Organic - Odyssey number 36 Chap.14 - Carbonyl Compounds topic.

I have never seen this reaction that happens after the Hoffman reaction.

The two confusing things I find from this question are :

1) When Br2 attaches Ortho/Para it is usually always done through using a Louis Acid Catalyst since this is an EAS reaction...........but we just use Br2 over h20 in this one and it works ?

2) When Br2 attaches in an EAS reaction we usually get the Ortho + Para products BUT in this case, we get ONE product that has BOTH Ortho and Para added to the same benzene ? I remember adding both Orth and Para to one product being wrong from my notes.....

 

[DAT Destroyer]

Organic - Odyssey number 36 Chap.14 - Carbonyl Compounds topic.

I have never seen this reaction that happens after the Hoffman reaction.

The two confusing things I find from this question are :

1) When Br2 attaches Ortho/Para it is usually always done through using a Louis Acid Catalyst since this is an EAS reaction...........but we just use Br2 over h20 in this one and it works ?

2) When Br2 attaches in an EAS reaction we usually get the Ortho + Para products BUT in this case, we get ONE product that has BOTH Ortho and Para added to the same benzene ? I remember adding both Orth and Para to one product being wrong from my notes.....

A perspicacious student you are !!!! The NH2 group is a SUPER activator,,,,,it is so reactive they we don't even need a Lewis acid catalyst !!! In real life, it would be a waste of money . Note that the reaction didn't just give a single bromination , but both ortho positions and the para position are brominated. In lab, we often use protecting groups such as acetyl chloride when dealing with the NH2 group on a benzene ring. If you need to read more on this, The Maitland Jones text as well as the David Klein text do a wonderful job. Great question. I hope this helps.

Dr. Romano

 

[Mrhyde]

A perspicacious student you are !!!! The NH2 group is a SUPER activator,,,,,it is so reactive they we don't even need a Lewis acid catalyst !!! In real life, it would be a waste of money . Note that the reaction didn't just give a single bromination , but both ortho positions and the para position are brominated. In lab, we often use protecting groups such as acetyl chloride when dealing with the NH2 group on a benzene ring. If you need to read more on this, The Maitland Jones text as well as the David Klein text do a wonderful job. Great question. I hope this helps.

Dr. Romano

@orgoman22 .... Interesting. I was expecting a ortho + para product , something like this https://upload.wikimedia.org/wikipedia/commons/d/d4/AromaticChlorination.png
So ortho and para being on the same one product instead of having an ortho + para product, happens in this case just because NH2 is seen as a "super activator" ?

Thank you 🙂