November 01, 2024, 01:31:26 AM
Forum Rules: Read This Before Posting


« previous next »
Pages: [1]   Go Down

Topic: Iodine addition on alkenes  (Read 7728 times)

0 Members and 1 Guest are viewing this topic.

Offline mir

  • Fascinated organic chemist
  • Chemist
  • Full Member
  • *
  • Posts: 310
  • Mole Snacks: +13/-3
  • Gender: Male
  • Visit my blog: mir.humle.be
    • My humble homepage with norwegian articles
Iodine addition on alkenes
« on: May 26, 2006, 10:16:17 AM »
I guess I have figured out the upper mechanism.
But the lower reaction is causing me to bite my nails and drinking to much coffee. All in all, I need help. On monday I have an oral exam in physcial org chemistry :-/
Logged
No single thing abides, but all things flow.
Fragment to fragment clings, and thus they grow
Until we know and name them.
Then by degrees they change and are no more
The things we know.
- Titus Lucretius Carus

http://www.ife.no

Offline Dan

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 4716
  • Mole Snacks: +469/-72
  • Gender: Male
  • Organic Chemist
    • My research
Re: Iodine addition on alkenes
« Reply #1 on: May 26, 2006, 11:19:10 AM »
How about this:

1. Form the iodonium ion as normal
2. Decarboxylate to open the 3 mem ring
OR
Open to give the tertiary carbocaton, which is rapidly trapped by the CO2H, forming a 4 membered ring
Reverse [2+2] cycloaddition, eliminating CO2

3. SN2 by water
Logged
My research: Google Scholar and Researchgate

Offline Dan

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 4716
  • Mole Snacks: +469/-72
  • Gender: Male
  • Organic Chemist
    • My research
Re: Iodine addition on alkenes
« Reply #2 on: May 26, 2006, 11:53:26 AM »
Like this http://users.ox.ac.uk/~some1599/Images/mech.jpg

It's a bit scruffy, but I had to use use paint, so...
Logged
My research: Google Scholar and Researchgate

Offline movies

  • Organic Minion
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1973
  • Mole Snacks: +222/-21
  • Gender: Male
  • Better living through chemistry!
Re: Iodine addition on alkenes
« Reply #3 on: May 26, 2006, 01:17:33 PM »
How about just forming the diiodide, then deacarboxylate and eliminate one of the I's, then SN2 (or SN2') with water to displace the other.
Logged

Offline Dan

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 4716
  • Mole Snacks: +469/-72
  • Gender: Male
  • Organic Chemist
    • My research
Re: Iodine addition on alkenes
« Reply #4 on: May 26, 2006, 02:19:08 PM »
Yeah that seems more likely, seeing as KI about, good call.
Logged
My research: Google Scholar and Researchgate

Offline mir

  • Fascinated organic chemist
  • Chemist
  • Full Member
  • *
  • Posts: 310
  • Mole Snacks: +13/-3
  • Gender: Male
  • Visit my blog: mir.humle.be
    • My humble homepage with norwegian articles
Re: Iodine addition on alkenes
« Reply #5 on: May 26, 2006, 04:58:38 PM »
Quote from: movies on May 26, 2006, 01:17:33 PM
How about just forming the diiodide, then deacarboxylate and eliminate one of the I's, then SN2 (or SN2') with water to displace the other.

Like this?

I wasnt sure about the decarboxylation step.
I understand now. In such problems, you have to dare to use the imagination.
Even if you have to form a sterically extreme cyclobutane-like ring.
Logged
No single thing abides, but all things flow.
Fragment to fragment clings, and thus they grow
Until we know and name them.
Then by degrees they change and are no more
The things we know.
- Titus Lucretius Carus

http://www.ife.no

Offline movies

  • Organic Minion
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1973
  • Mole Snacks: +222/-21
  • Gender: Male
  • Better living through chemistry!
Re: Iodine addition on alkenes
« Reply #6 on: May 28, 2006, 06:51:52 PM »
Not quite, I was thinking that the second compound you have drawn there would decarboxylate with the electrons from the C-C bond that you would break kicking down to diplace the adjacent I and from the C=C double bond.
Logged
Pages: [1]   Go Up
« previous next »
Sponsored Links