[ricecake]

Ethybenzene + HNO₃/H₂SO₄,t°  A + KMnO₄,t° +H₂O B+Na₂S,t°  C +HNO₂,0-5°C,HBF₄,t°

Please help with this problem. I am a bit iffy about the position of NO₂ group and Na₂S

A would be p-nitroethylbenzene?
B would be
C would be
D would be

[Dan]

1. Your nitro groups have gone crazy. I assume this is a SMILES typo - use N(=O)=O, not N=O=O.
2. Look up the regioselectivity of permanganate oxidation of aromatic hydrocarbons.
3. So you are suggesting Na₂S reduces an acid to a hydrated aldehyde. You are on the right track with reduction, but it won't reduce the carboxylic acid - something else...
4. It looks like you have identified this as diazonium chemistry - but, have you ever seen the formation of diazonium salts from nitroarenes? What functional group normally forms a diazonium with HNO₂? This gives you a big clue about step 3.

[ricecake]

Thank you so much for your help.
Yes, step B was a smiles typo. Is this closer to the correct answer?

A is still p-nitroethylbenzene
B is p-nitrobenzoic acid (the CH₃ will fall off from the branch)
C is
D is