5
$\begingroup$

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:

$\endgroup$
3
$\begingroup$

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

$\endgroup$
  • $\begingroup$ 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 Dec 11 '15 at 18:12
  • $\begingroup$ That's all. Your starting material is chiral, and all of the products will chiral. $\endgroup$ – A.K. Dec 11 '15 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 Dec 11 '15 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. Dec 11 '15 at 20:03
  • 1
    $\begingroup$ No, you're good now. I just forgot that a chiral center was formed on 2-bromo-3,4-dimethylpentane. $\endgroup$ – A.K. Dec 11 '15 at 20:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.