How does Diazonium salt work?

[sfoksn]

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Hello, if we have p-nitro bromobenzene and we treat it with Cl2/H2O, we get a diazonium salt.

How exactly does this happen?

I thought it would not be favorable to break the aromaticity of the benzene so the Cl would not be able to kick off the H and replace itself.


Can anyone provide me why?


Thank you.

 

[sfoksn]

why doesn't anybody answer my questions?

is it too complicated?

bump

 

[AmpedUp]

^I'll look this up for you. I'm going through my old OChem notes. I know we discussed it somewhere. When I find it, I'll scan/transcribe it onto here. that is if no one else answers...I'm also curious as well

 

[sfoksn]

Thanks.. if you look at my other questions, no one answers my question very clearly..

its weird 🙁

 

[AmpedUp]

are you sure about the reagents (Cl2/H2O)?

because nitrobenzene should be treated with Zn/HCl or SnCl2/HCl to make the diazonium salt...but I guess you could infer (if these are your actual reagents) that the nitrobenzene has been reduced to an aminobenzene (with H from H2O donated to this structure to form the diazonium salt). At least that's what I'm seeing from my notes that I took a few years ago...

 

[sfoksn]

Hm.. yeah.. I think when I posted I was too sleepy.. Here is the picture:


So the benzene with Br and NH2 gets treated with Cl2/H2O and Cl2 is able to replace the H's on benzene, and I am very confused about that.

Also, when the third benzene (Br, NH2, Cl, Cl) gets treated with NaNO2, HCl at 5 celcius, it gets turned into salt... Could you tell me why?

Then H3PO2 is able to kick off the N2+ Cl- salt group from the benzene..

I do not understand any of the mechanisms and why it happens..

Sorry about the error, AmpedUp!

 

[sfoksn]

oh man, picture came out badly.

click on it to rotate the picture 🙂

 

[sfoksn]

bump

 

[redchesus]

I think that's because NH2 is a o/p director (and activating) in electrophilic substitution. At these two positions, the unshared electrons on NH2 can stabilize the carbocation but at the meta position they can't.

Br is also o/p directing, but it is deactivating and I've learned that you always go with the activator.

 

[sfoksn]

bump