another ochem question

[sherry225]

Sorry to bombard the forum with more questions.....

If (HNO3, H2SO4) are added to a benzene ring with a NH2 group attached to it, will the NH2 become NO2? or is the NO2 will get attached to the ring? I think one of the topscore question has the NO2 attach to the ring and I remeber seeing somewhere that the NO2 replace NH2. Is there some special rules for this?

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[jheidenr]

This is an example of electrophilic aromatic substitution. The amine group is a stong activating substituent of the benzene ring, therefore othro- para- directing. The mixture of nitric acid and sulfuric acid will create a nitronium ion intermediate, the most favorable position for the ion to form would be in the para position.

The nitro group would not become reduced, that would require something like Zn with diluted HCl.

 

[sherry225]

I remember reading in Kaplan book that the NH2 on the ring forms diazonium salt with (HNO2, H2SO4)? (By the way, the ring also has a Br group on the para postition. Then in this situation, how come NO2 didn't get attached to ortho?

 

[jheidenr]

Sorry, I didn't have the question in from of me to look...it would go to the ortho position.

As for the diazonium salf formation...that is with HNO2/H2SO4 (nitrous) not HNO3/H2SO4 (nitric)

 

[sherry225]

Thanks! I didn't notice that!