December 19, 2024, 02:16:36 AM
Forum Rules: Read This Before Posting


Topic: 1,4-diphenyl-1,3-butadiene NMR  (Read 8785 times)

0 Members and 1 Guest are viewing this topic.

Offline CJ2347

  • Very New Member
  • *
  • Posts: 2
  • Mole Snacks: +0/-0
1,4-diphenyl-1,3-butadiene NMR
« on: February 17, 2014, 09:34:13 PM »
Recently in lab, we synthesized the above named product though the reaction of cinnamaldehye with benzyl triphenylphosphonium chloride. And then analyzed the product with an NMR in order to determine which stereoisomer was formed. The coupling constants indicate that the E,E isomer was formed. The integration given on the readout for the aromatic peaks is 7.15. Isn't this value to high? Shouldn't it be around 5? Why is it higher?

Offline discodermolide

  • Chemist
  • Sr. Member
  • *
  • Posts: 5038
  • Mole Snacks: +405/-70
  • Gender: Male
    • My research history
Re: 1,4-diphenyl-1,3-butadiene NMR
« Reply #1 on: February 17, 2014, 10:27:33 PM »
Obviously 2 of the C=C protons appear under the aromatic signals, increasing the integral by 2.
Development Chemists do it on Scale, Research Chemists just do it!
My Research History

Offline CJ2347

  • Very New Member
  • *
  • Posts: 2
  • Mole Snacks: +0/-0
Re: 1,4-diphenyl-1,3-butadiene NMR
« Reply #2 on: February 18, 2014, 10:19:33 PM »
I don't understand. I thought the the two doublets of doublets represented the vinylic protons.

Offline discodermolide

  • Chemist
  • Sr. Member
  • *
  • Posts: 5038
  • Mole Snacks: +405/-70
  • Gender: Male
    • My research history
Re: 1,4-diphenyl-1,3-butadiene NMR
« Reply #3 on: February 19, 2014, 12:43:09 AM »
Looks like all the aromatics are more or less together.
« Last Edit: February 19, 2014, 01:18:52 AM by discodermolide »
Development Chemists do it on Scale, Research Chemists just do it!
My Research History

Offline clarkstill

  • Chemist
  • Full Member
  • *
  • Posts: 477
  • Mole Snacks: +77/-4
Re: 1,4-diphenyl-1,3-butadiene NMR
« Reply #4 on: February 19, 2014, 02:26:18 AM »
If it's a weak NMR sample in CDCl3 there may also be a large CHCl3 peak underneath the aromatic region, which you could be including in your integration by accident.

Sponsored Links