Chlorination vs. Bromination

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EmanUT

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Can anyone quickly clarify the differences in adding Br2 vs. Cl2 in light/heat. Since this is free radical halogenation, do they both simply add to the most stable carbocation? Also, since Cl2 is more reactive than Br2, what effects does this have? Thanks guys!
 
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EmanUT said:
Can anyone quickly clarify the differences in adding Br2 vs. Cl2 in light/heat. Since this is free radical halogenation, do they both simply add to the most stable carbocation? Also, since Cl2 is more reactive than Br2, what effects does this have? Thanks guys!
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Whoa, NO CARBOCATION INVOLVED IN FREE RADICAL HALOGENATION EVER!!!!!! They give the most stable FREE RADICAL
 
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EmanUT said:
Can anyone quickly clarify the differences in adding Br2 vs. Cl2 in light/heat. Since this is free radical halogenation, do they both simply add to the most stable carbocation? Also, since Cl2 is more reactive than Br2, what effects does this have? Thanks guys!
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It doesn't really sound like you have a specific question. Free radical halogenation is about the simplest concept you will tackle in O-Chem. It sounds like you are in O-Chem 1, but it would seem to me that you would be tackling conjugated systems at this point in the semester.

As far as what is the difference between CL2 and Br2, in general if you can use chlorine you can also use bromine. There are some exceptions, but I'm sure your professor/book will cover it when the time is right.
 
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Hardbody said:
It doesn't really sound like you have a specific question. Free radical halogenation is about the simplest concept you will tackle in O-Chem. It sounds like you are in O-Chem 1, but it would seem to me that you would be tackling conjugated systems at this point in the semester.

As far as what is the difference between CL2 and Br2, in general if you can use chlorine you can also use bromine. There are some exceptions, but I'm sure your professor/book will cover it when the time is right.
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In addition to what everyone else said, bromination is more selective than chlorination. So that means you'll get about a 60:40 ratio between chlorines added to a secondary carbon to chlorines added to a primary carbon. On the other hand, bromination would give about a rough 97:3 estimate between bromines added to a secondary carbon to bromines added to a primary carbon. Either way, when in light, these halogens add to carbons via the free radical mechansim. Your textbook should give a good outline of the details of the mechanism.
 
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EmanUT said:
Can anyone quickly clarify the differences in adding Br2 vs. Cl2 in light/heat. Since this is free radical halogenation, do they both simply add to the most stable carbocation? Also, since Cl2 is more reactive than Br2, what effects does this have? Thanks guys!
Click to expand...

For both Cl2 and Br2 they favor the more stable free radical position: tertiary > secondry> primary.

For Cl2 thou, the ractivity ratio is 5.5 (tertiary)>4.5 > 1 (primary) and for Br2 the reactivity ratio is 1700 (tertiary)> 97 > 1 (primary) --> so you'll rarely see a bromination for a primary free radical position.
 
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