4
$\begingroup$

For (a) (iii), how do you get the second product listed in the answers manual? I just can't visualize it.

What about (c) (i), why are there three resonance structures? If a hydrogen is taken away from a specific carbon of the initial molecule to have a radical, there is no way you can have three resonance structures.

$\endgroup$

1 Answer 1

3
$\begingroup$

The barrier to rotation in the allyl radical is low (~15-16 kcal/m) and it can undergo cis-trans isomerization.

enter image description here

As to question (c)(i), you're right, there are only two resonance structures.

enter image description here

What you show above with three resonance structures is the trimethylenemethane diradical, isobutene with 2 allylic hydrogens removed.

$\endgroup$
6
  • $\begingroup$ ron, what are the dotted lines? Why is there a positive charge? $\endgroup$
    – yolo123
    Sep 27, 2014 at 18:43
  • $\begingroup$ the delocalized allyl radical, a shorthand way of drawing the 2 resonance structures; no positive charge, it is a radical, so just 1 unpaired electron. $\endgroup$
    – ron
    Sep 27, 2014 at 18:44
  • 1
    $\begingroup$ The symbol that might look like a plus sign is just how my drawing software draws a radical. $\endgroup$
    – ron
    Sep 27, 2014 at 18:47
  • $\begingroup$ Oh, ok. I didn't know this barrier to rotation was so easy. It seems that Solomons' textbook does not discuss this. :O Thanks for the info. $\endgroup$
    – yolo123
    Sep 27, 2014 at 19:21
  • 1
    $\begingroup$ @yolo123 I'll edit my answer to cover this. $\endgroup$
    – ron
    Sep 27, 2014 at 20:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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