Question

Can somebody be kind and elucidate the difference between Bromine and Chlorine regarding Selectivity in Free Radical Reactions?!

Answer 1

Well, for a basic introductory organic chemistry course, all you really need to know is that it follows markovnikov's rule (I think that's the name of the rule), meaning that the halogen(s) add to form the more stable product. As you might already know 3º>2º>1º

Answer 2

But, if you really want to get into a more detailed explanation, it has to do with activation energy and it really goes into some heavy thermodynamics.
Another thing you might want to consider is the product(s). HBr vs HCl.
Bonding is greater in HCl over HBr - without going into anything too complicated, think about the atomic size and orbital interaction.

Answer 3

I am pretty sure that any general chemistry book would have values for bond formation of HCl and HBr, which you can also use as a reference to see which is greater or less.

Answer 4

maybe @AravindG can "elucidate" some more information for you if you're still having some problems.

Answer 5

Chlorine has more tendency to undergo a kinetically controlled reaction and hence order of reaction is in the ratio 5:3.8:1 respectively for tertiary,secondary and primary. Bromine has tendency for a thermodynamically controlled reaction ratio is around 1600:80:1.

Answer 6

@abb0t Thanks Abb0t! btw, the word elucidate is used in my town more than the word 'explain', don't really know why lol. thanks for elucidating :P