[souzami4]

What is the major organic product obtained from the following sequence of reactions?
Toluene -> Na2Cr2O7/H2SO4 -> Br2/FeBr3
a) 3-bromobenzoic acid
b) 2-bromobenzoic acid
c) 4-bromobenzoic acid
d) benzoyl bromide

So far, I know that Na2Cr2O7 changes the toluene to benzoic acid. My next step would be to add a bromine to the ortho or para position, but I know the answer is in the meta position. Why?

Thank you.

Michelle

[orgopete]

I missed the class on groups that direct o/ vs meta. What did your professor say?

[souzami4]

My professor only went over activating vs activating groups. Even if bromine is considered a deactivating croup, it would typically form in the o/p orientation. So there must be something I'm missing if it is oriented in the meta position

[sjb]

My professor only went over activating vs activating groups. Even if bromine is considered a deactivating croup, it would typically form in the o/p orientation. So there must be something I'm missing if it is oriented in the meta position

It's not a case of the directing effects of the incoming group, more of the group already in position...

[souzami4]

Can you be more direct? I don't want to spend days trying to figure this out. Thanks.

[souro10]

Can you be more direct? I don't want to spend days trying to figure this out. Thanks.

You probably want this kind of an answer, but I don't think it's helpful towards learning the chemistry:

You have benzoic acid. The substituent -COOH attached to the benzene ring directs electrophiles to the meta position. This will be clear if you try to draw the resonating structures. Br₂ and FeBr₃ would produce nothing but Br⁺ , an electrophile. Hence, the answer.

[souzami4]

thank you!