OChem!

[Jab1113]

Quick OChem question.

I understand that on a benzene ring, we have o-/p- directors and m- directors. EWG/EDG. K cool no problem.

Question: So how do I know when to add to the benzene ring in the o-/p- vs. m- or simply attacking the group attached to the carbon....

So for example,

If i have a benzene ring with a methyl group attached to it (toluene in this case), and I want to add bromine by doing free radical bromination (Br2/heat), how do I know to attack the carbon and not add o-/p-?

Ive attached a picture to help explain my question:

http://i1136.photobucket.com/albums/n488/Jab1113/topscore.jpg

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[Golfguy]

The answer is B, via a radical mechanism. The benzylic carbon produces a very stable radical when an H is removed.

Addition to the benzene ring would require FeBr3 or other catalyst.

 

[bharat008]

The answer is B, via a radical mechanism. The benzylic carbon produces a very stable radical when an H is removed.

Addition to the benzene ring would require FeBr2 or other catalyst.

+1..

Remember, if you don't have catalyst such as FeBr3 or AlCl3 then you never attack at ortho or para or meta.. Always look for C that are attached to the benzene ring such as CH3 in this case and attack there..

Hope that helped..

 

[Jab1113]

You guys rock! thank you

 

[bharat008]

You guys rock! thank you

We know that...

 

[wired202808]

You guys rock! thank you

jab, please remember what Br2 with light does, it replaces a Hydrogen with a Br. However, since the ring is conjugated and contains double bonds it would not be able to attack it and instead attacks the carbon outside of the ring. Usually the first carbon (meaning the a 2nd or 3rd degree carbon)

on the other hand if you simply had cyclohexane, then the answer would have a carbon with a Br and a CH3. hope this helps.

 

[Jab1113]

jab, please remember what Br2 with light does, it replaces a Hydrogen with a Br. However, since the ring is conjugated and contains double bonds it would not be able to attack it and instead attacks the carbon outside of the ring. Usually the first carbon (meaning the a 2nd or 3rd degree carbon)

on the other hand if you simply had cyclohexane, then the answer would have a carbon with a Br and a CH3. hope this helps.

makes sense! thanks for the follow up