[NewtoAtoms]

Complete the following reaction by supplying the missing reactant(s)

C₆H₅NO₂ + ? ----------> C₆H₅N₂⁺Cl^-

a.  HCl, Fe                                NO - this reaction is only nitration, leaving a benzene ring with a NH2 substitutent not desired product
b.  H2, Ni, then CuCl                   PERHAPS - this is perplexing to me... is the desired product an intermediate of the final product created here?
c.  Hcl, Fe, then NaNo2, HCl         This is incomplete, there is nitration, then the aryl diazonium ion + INCOMPLETE???
d.  NaNO2, HCl                           This is also incomplete
e.  HCl, Fe, then H2PO2, HCl        NO - this is reductive deamination reaction therefore the result would be benzene ring not desired product.

Therefor I would have to say that B is correct,
Does anyone agree with me???

Thank you for your time.

Newtoatoms

[macman104]

I disagree.  You are also getting your terms very mixed up.

a)  This is not a nitration, this is a reduction
b)  This is not the correct sequence, H2 and Ni are again a reduction
c)  I don't even know what you mean by your sentence here.  Why do you think this is incomplete?  You say you get a diazonium at the end, isn't that what you want?
d)  These may not even react
e)  Not familiar with what the H2PO2 will do, but it's not correct.

[alphahydroxy]

Try looking up:


Hydrogenation of nitro groups

Diazotisation

The Sandmeyer reaction


If you look at the mechanisms of these reactions, the answer to your question (and the purpose of such a transformation) should become clear...

[NewtoAtoms]

I am going to post my leg work so that I can make it clear that I have done the work, but I need a bit of assistance:

a.  C6H5-NO2 + HCl, Fe ---> C6H5-NH2 (not desired product)
b.  C6H5-NO2 + H2, Ni  ---> C6H5-NH2 + CuCl BUT MISSING the diazonium -NaNO2, HCl, H2O ---> therefore this one is possible.
c.  C6H5-NO2 + HCl, Fe ---> C6H5-NH2 + NaNO2, HCl ----> GREAT but what are we adding? that's what I meant by not complete (not desired product)
d.  C6H5-NO2 + NaNO2, HCl ---> DOESNT work because we can't add the diazonium before changing NO2 to NH2 (not desired product)
e.  C6H5-NO2 + HCl, Fe ---> C6H5NH2 + H3PO2, HCl ---> Benzene ring (reductive deamination) (not desired product)

Having done all these reactions I would have to conclude that b is the correct answer.
My only issue is that because the diazonium-NaNO2, HCl, H20 are missing is that why we get the C6H5N2+Cl-???

Thank you for your time.

[DrCMS]

Think again.

a) you're correct with this, it is a Bechamp reduction.
b) this is another reduction followed by the addition of CuCl what reaction do you think that last step might cause?
c) is a Bechamp reduction followed by a diazotisation, giving?
d) you're correct
e) you're correct again

Think about the 2nd steps in b and c, what happens when you react an aromatic amine with
b) CuCl
c) NaNO2 / HCl

Now which do you think is correct?

[macman104]

I think you are confused by the question.  Based on you saying "GREAT but what are we adding?"  You are adding each of the possible options to the nitrobenzene and choosing the option that result in the formation of a diazonium.

[NewtoAtoms]

Hello to all my replyers,
I am very grateful for all your help.

I am sorry I was misunderstanding the step of the aryl diazonium ion. 

My apologies, however after going back a few more times and re-reading. I think maybe I have it:

C.  C6H5-NO2 + HCl, Fe ---> C6H5-NH2 ---> C6H5N=N + HCl ---> C6H5N=N+CL- IS CORRECT

Thank you for your patience!!

Newtoatoms