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My organic chemistry final is next Tuesday, and I have worked through the practice final. The last question is the following: Give and name all the compounds resulting from the radical monobromination 2,3-dimethylpentane. Indicate the major and minor products.

I drew:

My prof says that I am missing my R/S. I can clearly see my chiral centres, but how do I determine the orientation of the H? Red is the major product, blue is the minor product, and magenta is the very minor product.

The second question is: write the mechanism of this reaction identifying the initiation, propagation, and termination steps for the formation of one of the products. This is what I drew:

My prof says that I am missing a propagation step with another bromine-bromine molecule.

EDIT:

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My prof says that I am missing my R/S. I can clearly see my chiral centres, but how do I determine the orientation of the H? Red is the major product, blue is the minor product, and magenta is the very minor product.

You don't determine the orientation of the H you just acknowledge the formation of both the R and S stereo isomers in your products in 50/50 proportions.

My prof says that I am missing a propagation step with another bromine-bromine molecule. I would greatly appreciate your input!

All you need to show is the organic radical reacting with diatomic bromine to form you brominated molecule and another bromine radical.

Bromine Propigation

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  • $\begingroup$ Thank you very much! That's what I thought. So I simply mention the 50/50 ratio where appropriate (i.e. where there is a chiral carbon), right? $\endgroup$
    – Johnathan
    Commented Dec 11, 2015 at 18:12
  • $\begingroup$ That's all. Your starting material is chiral, and all of the products will chiral. $\endgroup$
    – A.K.
    Commented Dec 11, 2015 at 19:07
  • $\begingroup$ Thanks! I have edited my question: I can see it now. The molecules have either 1 or 2 chiral centres. $\endgroup$
    – Johnathan
    Commented Dec 11, 2015 at 19:54
  • $\begingroup$ Not quite. do 2-bromo-2,3-dmethylpentane and 2-bromo-3,4-dmethylpentane have 2 chiral centers or 1? $\endgroup$
    – A.K.
    Commented Dec 11, 2015 at 20:03
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    $\begingroup$ No, you're good now. I just forgot that a chiral center was formed on 2-bromo-3,4-dimethylpentane. $\endgroup$
    – A.K.
    Commented Dec 11, 2015 at 20:09

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