July 04, 2020, 05:45:13 PM
Forum Rules: Read This Before Posting


Topic: Pechmann Condensation mechanism  (Read 12458 times)

0 Members and 1 Guest are viewing this topic.

Offline Tiger

  • Retired Staff
  • Full Member
  • *
  • Posts: 158
  • Mole Snacks: +15/-5
  • Gender: Female
  • When I'm with you Eternity is a step away
Pechmann Condensation mechanism
« on: November 11, 2004, 01:06:22 AM »
Please help me with the second part of the mechanism. I got the first part but I'm not sure how to get to the product.

Here is the link to the reaction

http://themerckindex.cambridgesoft.com/TheMerckIndex/NameReactions/ONR295.htm

Thanks

JN

Offline Tiger

  • Retired Staff
  • Full Member
  • *
  • Posts: 158
  • Mole Snacks: +15/-5
  • Gender: Female
  • When I'm with you Eternity is a step away
Re:Pechmann Condensation mechanism
« Reply #1 on: November 11, 2004, 02:21:38 AM »
How can I obtain this article?

H. v. Pechmann, C. Duisberg, Ber. 16, 2119 (1883)

Offline Mitch

  • General Chemist
  • Administrator
  • Sr. Member
  • *
  • Posts: 5294
  • Mole Snacks: +376/-2
  • Gender: Male
  • "I bring you peace." -Mr. Burns
    • Chemistry Blog
Re:Pechmann Condensation mechanism
« Reply #2 on: November 11, 2004, 02:18:06 PM »
It's in german.
Most Common Suggestions I Make on the Forums.
1. Start by writing a balanced chemical equation.
2. Don't confuse thermodynamic stability with chemical reactivity.
3. Forum Supports LaTex

Offline movies

  • Organic Minion
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1973
  • Mole Snacks: +222/-20
  • Gender: Male
  • Better living through chemistry!
Re:Pechmann Condensation mechanism
« Reply #3 on: November 11, 2004, 04:37:41 PM »
So I assume you got through the trans-esterification part.

The next step is formation of the enol tautomer of the beta-keto ester.  From there the Lewis acid can activate the remaining carbonyl group to do a Michael addition to form the second ring.  Then you just eliminate water to form the enone.

Offline Tiger

  • Retired Staff
  • Full Member
  • *
  • Posts: 158
  • Mole Snacks: +15/-5
  • Gender: Female
  • When I'm with you Eternity is a step away
Re:Pechmann Condensation mechanism
« Reply #4 on: November 12, 2004, 01:19:21 AM »
Thanks to Mitch and Movies.

I went to the library and found that article. The book was so so so so old and smelly. It's in German. I had someone translate the article for me.

JN

Offline AWK

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 7378
  • Mole Snacks: +516/-86
  • Gender: Male
Re:Pechmann Condensation mechanism
« Reply #5 on: November 12, 2004, 02:06:49 AM »
In this reference you will not find any information on mechanism. This is
multiple-transformation process which involves hydroxyalkylation at 2-position of substituted phenol, transesterification and dehydration
AWK

pumpkins

  • Guest
Re:Pechmann Condensation mechanism
« Reply #6 on: November 12, 2004, 10:36:52 AM »
probably it goes like this:

Offline Mitch

  • General Chemist
  • Administrator
  • Sr. Member
  • *
  • Posts: 5294
  • Mole Snacks: +376/-2
  • Gender: Male
  • "I bring you peace." -Mr. Burns
    • Chemistry Blog
Re:Pechmann Condensation mechanism
« Reply #7 on: November 12, 2004, 02:25:41 PM »
Thanks Pumpkins.

Nothing smells better than an old German book. :P
Most Common Suggestions I Make on the Forums.
1. Start by writing a balanced chemical equation.
2. Don't confuse thermodynamic stability with chemical reactivity.
3. Forum Supports LaTex

Offline Tiger

  • Retired Staff
  • Full Member
  • *
  • Posts: 158
  • Mole Snacks: +15/-5
  • Gender: Female
  • When I'm with you Eternity is a step away
Re:Pechmann Condensation mechanism
« Reply #8 on: November 13, 2004, 12:07:20 AM »
Thanks Pumpkins.

Nothing smells better than an old German book. :P

Yup, it's very smelly. I finished my paper last night and turned in today. I have to do a presentation on Pechmann condensation. I haven't done this type of presentation before. Any suggestion??? My prof said that he didn't like Power Point or anything.. use chalk and board...

Offline movies

  • Organic Minion
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1973
  • Mole Snacks: +222/-20
  • Gender: Male
  • Better living through chemistry!
Re:Pechmann Condensation mechanism
« Reply #9 on: November 14, 2004, 12:41:01 PM »
I would start by showing the general transformation for the condensation, then talk about the proposed mechanism.  If you could find some examples of the reactions use in synthesis, that would be a nice addition as well.  You could show where the Pechmann was used in the synthesis and then how that maps onto the final target molecule.  There are a lot of natural products that contain coumarin rings.

Offline Tiger

  • Retired Staff
  • Full Member
  • *
  • Posts: 158
  • Mole Snacks: +15/-5
  • Gender: Female
  • When I'm with you Eternity is a step away
Re:Pechmann Condensation mechanism
« Reply #10 on: November 23, 2004, 03:01:58 AM »
My prof just gave me back my research paper. Oh my goodness, after I took the paper from his hands I hardly saw any black ink on the paper, all red ink  :-[ :'(

Sponsored Links